PVB

Winterize Backflow Preventer

PVB Backflow Preventer
PVB Backflow Preventer

It’s a Sunday night in November and you’re heading to bed when it suddenly occurs to you….your irrigation system is still on and it’s going to be crazy cold tonight!

How could it be this cold?!? Wasn’t Halloween like a week ago? And wasn’t that trip to the beach like two weeks ago? How does time move so quickly? How are the days so incredibly short already? It’s only 3:30pm and it’s already dark. How is that possible?!?

Winter is coming ? Winter is here
Winter is coming ? Winter is here

Okay, stay calm and don’t give yourself an existential dread induced panic attack. Now is the time to practice that deep breathing technique that your YouTube yoga instructor is always going on about.

Namaste
Namaste

Take a deep breath and relax. You may not have time to get a licensed lawn sprinkler system contractor out to blow out a sprinkler system, but you can at least buy yourself some time. 

Sweet, precious, time. There may not be much of it left, but there is enough to get you to bed in the next 15-30 minutes. That is, if you can keep taking those deep breaths and be cool, Yolanda.

DISCLAIMER: This information on this site is for entertainment purposes only. The authors and owners of this site accept no responsibility or liability for any actions taken by readers. If you are not comfortable attempting repairs, please hire a licensed professional. Thank you!

What you will need:

  • Flathead screwdriver
Flathead screwdriver
Flathead screwdriver
  • Work gloves
Work gloves
Work gloves
  • Channel Lock pliers or adjustable pliers
Channel Locks or adjustable pliers
Channel Locks or adjustable pliers

We have established that we can’t get a lawn sprinkler system contractor out to winterize an irrigation system in the middle of the night, so that’s not going to happen. And even if you have an air compressor and can follow instructions and winterize a sprinkler system, it’s too late at night to be considering that option.

You do not need the cops showing up and issuing you a ticket for a noise ordinance violation because you’re running your very loud air compressor at midnight. And you definitely don’t need your HOA board member neighbor Janet with the too-perfect hydrangeas ringing your doorbell and hassling you.

So, what do you do? You drain backflow preventer and buy yourself some time.

How to Turn Off Backflow Preventer

FYI, not everyone is in a situation where a night or two of cold temperatures is going to damage their irrigation system, but if you have an above ground backflow preventer, it’s time to get to work and learn how to drain backflow preventer.

RPZ backflow preventer
RPZ backflow preventer

Most newer irrigation systems require an above-ground, exposed RPZ backflow preventer (reduced pressure backflow preventer) or PVB (pressure vacuum breaker) backflow preventer; but if your irrigation system was installed way back in the day when your closet was full of cavaricci pants and Mark Wahlberg was still going by the nom de plume, Marky Mark, then you might not need to worry too much.

PVB
PVB

In the past, many municipalities allowed new irrigation systems to be installed with what is called a dual check backflow preventer. This is a much cheaper backflow preventer than an RPZ backflow preventer or PVB sprinkler pressure vacuum breaker. A dual check is a much more basic design, and is often installed either underground or in the house (most often in the basement, if you are fortunate enough to have one of those sweet, sweet subterranean living spaces).

Dual check backflow preventer
Dual check backflow preventer

Turn Off Sprinkler Valve

If you have a basic dual check valve installed outside underground or inside your basement, to try to buy yourself a little time until you are able to get a lawn sprinkler system contractor out to blow out your irrigation system, the first step is to turn off the sprinkler system shut off valve. 

Sprinkler system shut off valve
Sprinkler system shut off valve

Then, once you have the sprinkler shut off valve turned off, you can turn on each zone or “station” on your irrigation controller to alleviate some of the pressure in the pipes. 

Turning on each zone at your irrigation controller is not necessarily going to drain a lot of water unless any of the pipes have been installed at an angle. This is because sprinkler valve diaphragms need a decent amount of pressure to open. But if it’s going to be very cold it may be worth a shot since you don’t have a lot of options in the short term.

Sprinkler controller
Sprinkler controller

Another more reliably effective option is to unscrew your sprinkler blow out or winterization point (a cap on your mainline pipe designed to allow an air compressor to be hooked up to blow the water out of your outdoor irrigation pipes). We will cover both of these methods in detail later on.

Sprinkler blow out cap
Sprinkler blow out cap

If you don’t know where your irrigation system shut-off valve is, here is an article with detailed instructions to help you find it: How to Turn off Sprinkler Valve.

PVC irrigation shut off valve
PVC irrigation shut off valve

Turn Off Sprinkler System

To turn off sprinkler system for winter, you will need to close the sprinkler main shut off valve. There are different irrigation shut off valve types. If you have a globe valve (a round handled valve), you will turn the globe valve clockwise (righty-tighty) until it is closed.

If your sprinkler main shut off valve is a ball valve (a valve with a tongue depressor shaped handle), you will need to turn the irrigation shut off valve handle 90° to turn off sprinkler system.

Start to close the sprinkler system shut off valve
Start to close the sprinkler system shut off valve
Continue to close the sprinkler system shut off valve
Continue to close the sprinkler system shut off valve
Finish closing the sprinkler system shut off valve
Finish closing the sprinkler system shut off valve

Don’t Turn off Water to House

The whole house water shut off valve can look very similar to the sprinkler system shut off valve, and they are often located right next to one another. If you think you may have turned off the whole house water shut off valve instead of the sprinkler water shut off valve, you can go to the main floor of your house and run the cold water to your kitchen or bathroom sink for at least 20 seconds or so.

Kitchen faucet running slow
Kitchen faucet running slow

You want to avoid using a sink in the basement for this test because gravity will drain all of the water from the pipes above the sink. So, if you use the sink in the basement, the water from the pipes on the main floor and the second floor (if you have a second floor) will also drain down and it may seem as though the water is on when in fact, it is not.

Kitchen faucet no water
Kitchen faucet no water

Once you have confirmed that your irrigation system shut-off valve is off, the next step will be to run your sprinkler controller manually for a few minutes for each zone to let gravity drain as much water as possible from the exposed pipe. 

Hunter Pro-C sprinkler controller
Hunter Pro-C sprinkler controller

Winterize Sprinkler System

If you live in a region where the temperatures drop below freezing in the winter, you will still need a sprinkler winterization. Draining the backflow valve and exposed pipe is just buying you a little time in an attempt to avoid freeze damage in the short term. Eventually, you will need to winterize sprinkler system.

Air compressor
Air compressor

Sprinkler Blow Out

Before you drain the backflow valve, you will need to find the sprinkler blowout point, which is a stubbed out threaded pipe that is designed for blowing out sprinkler system. If you know where your sprinkler blow out point is, you can also unscrew the cap. This will help drain even more water out of your pipes, which will further prevent freeze damage. 

Sprinkler cap
Sprinkler cap

* BEFORE YOU UNSCREW THE CAP, MAKE SURE THE WATER TO THE IRRIGATION SYSTEM IS OFF *

Make sure your irrigation shut off valve is off before unscrewing the cap
Make sure your irrigation shut off valve is off before unscrewing the cap

If your irrigation shut off valve is still on and you unscrew the cap completely, you will be unable to get the cap screwed back on until the sprinkler shut off valve is off; and that will be stressful and will waste water. And if there is one thing we hate more than just about anything here at Irrigation Skill, it is wasting water.

If you want to be absolutely certain that the sprinkler system shut off valve is off (and believe me, you do), go to your irrigation controller (or pull up your app if you have a Rachio or another smart sprinkler controller) and run a test cycle, or at least run one or two zones.

Hunter Pro-C controller
Hunter Pro-C controller
You can run a test cycle on your irrigation controller
You can run a test cycle on your irrigation controller
On this Hunter Pro-C sprinkler controller you press & hold the right arrow to turn on the system manually
On this Hunter Pro-C sprinkler controller you press & hold the right arrow to turn on the system manually
Or you can turn each zone on your irrigation controller on manually
Or you can turn each zone on your irrigation controller on manually

If you think you’ve turned off the in ground sprinkler shut off valve and you turn on a zone or two manually (or run a test cycle), and no sprinkler heads come up, that is probably confirmation that the water is off. Though, that’s not always a perfectly effective confirmation method, because the rain sensor may be preventing the system from running either because it has recently rained, or because the sprinkler rain sensor itself is malfunctioning. 

But it’s still worth trying to run the system from the irrigation controller because your rain sensor is probably not malfunctioning. And you should be able to bypass the rain sensor on your sprinkler controller to make sure any recent rain won’t keep the system off during this test.

If you do not know how to run the system manually from the controller, here is an instructional article on how to do so on a Hunter Pro-C. Even if you don’t have a Hunter controller, most controllers are pretty similar, so it may be worth checking out the article anyway.

Side note, if you have confirmed which valve is the sprinkler shut off valve, take a minute and label it! If the irrigation shut-off valve is inside, you can just label it with a standard label maker or with a label sticker that you can write on with a marker. Or if you have neither of those items, you can use a piece masking tape and a marker. Or cut a small rectangle out of a sheet of paper and stick it on with a piece of packing tape.

Label the irrigation shut off valve
Label the irrigation shut off valve

If the sprinkler system shut off valve is outside and you fear you may forget where it is located, write a note with the location details on it and stick the note to your irrigation controller (if it is located in your house or garage). If your sprinkler controller is located outside, maybe you can make a note and draw a crude map. You can then stick the map in your drawer or filing cabinet (or messy pile of papers in your closet) with your other random homeownery paperwork. 

You will thank yourself for taking a few minutes to label or document the location of the sprinkler system main water valve the next time you are inevitably in this exact same situation. One day your future self will love you for this.

Once you are certain that you were able to turn off sprinkler system water valve, you can get back to finding that pesky sprinkler blowout point so that you can drain pipes.

Your sprinkler winterization point is probably going to be a PVC, CPVC, or metal (most likely brass) threaded cap that should be teed off of your irrigation mainline pipe.

Sprinkler blow out cap
Sprinkler blow out cap

If your irrigation shut off valve is in your basement, your sprinkler blowout point will likely be up against the house somewhere; probably in a landscaping bed. 

Your sprinkler blow out could be:

  •  A white or brass cap randomly sticking out of the ground; often in a landscaping bed.
  • If the irrigation mainline pipe exits the house above the ground, the cap may just be somewhere on the pipe manifold that exits the wall and then runs underground.
  • Or it may be inside of an irrigation valve box. A valve box is basically an upside down bucket with a removable lid that is designed to provide relatively easy access to underground irrigation components.

Regardless of where the cap is located, you will likely need a pair of channel lock pliers or tongue and groove pliers to help provide additional leverage to help unscrew the sprinkler cap, if you cannot unscrew it by hand. This is because the sprinkler cap is connected to a threaded male adapter that should be wrapped in Teflon tape, which can make screwing it on and off a bit of a challenge. 

Sometimes the cap will only be hand tight and you will not need any assistance from adjustable pliers, but just in case, it’s best to have some “handy” (see what I did there?).

If your winterization or sprinkler blow out point (PVC, CPVC, or brass cap connected to your irrigation mainline) is inside of an irrigation valve box, you will need to pry up the lid of the valve box. You might be able to do this with your hand. If so, you ought to at least be wearing work gloves. You can try using your hand. If that doesn’t work, try using your channel locks or flathead screwdriver to get under the lip of the valve box and pry it up.

Use your adjustable pliers to pry up the lid of the valve box
Use your adjustable pliers to pry up the lid of the valve box

Once the lid has been removed and the sprinkler cap is visible and accessible, try to unscrew the cap by hand. If it’s on too tight, you will need your tongue and groove pliers. Adjust your channel locks to the appropriate settings so that you can grip the cap.

A sprinkler cap can break fairly easily, so *GENTLY*, grip the cap and start applying pressure in a counter-clockwise direction (lefty loosey). 

Gently grip the cap with your channel locks & slowly turn counter-clockwise
Gently grip the cap with your channel locks & slowly turn counter-clockwise
Keep gently & slowly turning the cap with your tongue and groove pliers
Keep gently & slowly turning the cap with your tongue and groove pliers

Once the sprinkler cap starts turning you can grip it with your hand and finish unscrewing the sprinkler cap. 

Once the cap has been loosened with your adjustable pliers, start to turn the cap with your hand
Once the cap has been loosened with your adjustable pliers, start to turn the cap with your hand
Do not fully remove the cap
Do not fully remove the cap

Do not unscrew the irrigation cap all the way. Unscrew it just enough to allow some water to drain out. Wait a minute or three to see if the pressure/flow starts to lessen and ease up. If the water flow lessens and starts to die down to a trickle, this is a good sign that you successfully turned off the water to the irrigation system.

If the water never stops flowing out of the sprinkler cap, then it is time to make sure that you actually turned off the correct valve. Again, do not fully unscrew the sprinkler cap until the water flow reduces significantly.

Once the water stops trickling out, you may finish unscrewing the irrigation cap.

Now that the water has ceased to flow, you may fully remove the cap
Now that the water has ceased to flow, you may fully remove the cap
Remove the cap to make sure all the water has leaked out
Remove the cap to make sure all the water has leaked out

You can either leave the cap unscrewed for now, until your irrigation contractor can fully blow out sprinkler or you can return the sprinkler cap to the pipe fitting and screw it back on (righty tighty, if you would like. The benefit to leaving it unscrewed is that if any water freezes and expands, it can exit the pipe. But if the cap is screwed back on, there will be nowhere for the water to go if it does expand beyond the pipes.

The benefit to loosely screwing the cap back on is that you won’t lose it. If you do choose to screw the cap back on, do not screw it all the way down. That way, if there is any ice that forms and the water expands, it will have somewhere to safely exit the pipes.

Now you may screw the cap back on in a clockwise direction
Now you may screw the cap back on in a clockwise direction, if you would like.
Continue to screw the cap back on
Continue to screw the cap back on. If you do screw the cap back on, it may be a good idea to leave it loosely connected to allow any water that might freeze room to expand and exit the pipes.

Okay, now that you have turned off the water to your irrigation system, it is time to drain backflow preventer sprinkler.

How To Drain Backflow Preventer

If you don’t know what kind of backflow preventer you have, check out this article. It has a guide and photos that will help you identify which model of backflow valve you have.

Once you have figured out whether you have an RPZ valve (reduced pressure zone backflow preventer), a PVB irrigation vacuum breaker, or a dual check backflow preventer, it’s time to grab your flat head screwdriver and get to draining.

Draining Sprinkler System Backflow

It is not possible to drain a dual check valve backflow preventer, so we will skip over that one.  

Dual check backflow preventer
Dual check backflow preventer

An RPZ backflow preventer or reduced pressure zone is the BMW of backflow preventers in that they are expensive, complicated, and prone to annoying maintenance issues. But, it makes sense that more and more municipalities are requiring them because unlike a dual check backflow preventer, you generally know when an RPZ reduced pressure zone assembly is not working…because they leak. Another benefit is that an RPZ reduced pressure valve can be tested and certified. 

RPZ backflow preventer
RPZ backflow preventer

The fact that they can be tested is great news because it’s the test cocks that the testing equipment connects to that can be opened to drain an RPZ backflow preventer. So, let’s learn how to shut off backflow preventer and drain it.

Backflow Preventer Drain

The test ports, “test cocks”, “bleeder valves”, or “backflow drains” are small stubbed out pieces of brass. The top of the test cocks have a groove that looks like a flathead screwdriver would fit perfectly into. This is because a flathead screwdriver will, in fact, fit perfectly into it. 

Backflow test cock
Backflow test cock

How to Drain Backflow Sprinkler

When the flathead screwdriver valve is running perpendicular to the test cock, this means that the test port is closed. When the valve is running parallel with the backflow test cock, that means that it is open.

The blue circled test cock on this RPZ backflow preventer is open & the black circled test cocks are closed
The blue circled test cock on this RPZ backflow preventer is open & the black circled test cocks are closed

The test cocks on your backflow preventer should be closed (perpendicular) if your irrigation system has been turned on this year. The backflow test cock valve can be turned 90° in either direction to either open or close the test port.

Drain Backflow

You can open all of the test ports on the backflow preventer one by one to drain as much water as possible. 

If you have a PVB pressure breaker valve, the process for draining it is very similar to draining an RPZ reduced pressure backflow preventer.

A PVB sprinkler system vacuum breaker also has backflow drains (test cocks) with flathead screwdriver shaped valves that can be turned 90° in either direction to open. Check out the PVB in the photo below with the test cocks labeled.

PVB with closed test cocks
PVB with closed test cocks

Much like unscrewing the cap, you also want to open the test cocks on your backflow preventer slowly. Again, if the water is still on to your irrigation system, it can release a huge amount of pressure and get water everywhere. So, please make sure the irrigation shut-off valve is off and open the backflow test cocks very slowly.

Drain Backflow Valve

When opening the first test port with a flathead screwdriver, please do so slowly. Even if the water is off, you can get a pretty serious burst of water. It is a much better idea to open the backflow test cocks slowly and let the pressure die down. Then, you can turn the backflow drain valve a little more until eventually there is no more water to drain out.

Depending on the type and model of backflow preventer, there are usually two to four test ports. They are small brass pieces that are stubbed-out of the backflow preventer itself. 

Test cock
Test cock

RPZ

An RPZ reduced pressure valve has four test cocks.

Please see the photo below with arrows pointing to the test ports on your backflow preventer:

The black arrows are pointing to the closed test cocks & the yellow arrow is pointing to an open test cock on this RPZ backflow preventer
The black arrows are pointing to the closed test cocks & the yellow arrow is pointing to an open test cock on this RPZ backflow preventer

In the photo, the BLACK ARROWS are pointing to CLOSED test ports. If the line on the test port is running perpendicular with the test port, the valve on the backflow test cock is closed.

Your test cocks will likely be closed.

If the line on the test port is running parallel with the test port itself, the valve on the test port is open. In the above photo, The YELLOW ARROW is pointing to an OPEN backflow drain port.

The test port valves can be opened by turning the backflow test cock valve 90° in either direction with a flathead screwdriver.

*AGAIN, if you decide that you would like to drain your backflow preventer to prevent possible freeze damage, before you open the test port valves on your backflow preventer TURN OFF THE IRRIGATION WATER VALVE.

If your irrigation system’s water valve is still on and you open the test ports, there will be a lot of water.

If your irrigation system’s water valve is off, some water will likely gush out for a few seconds, but then will slow and stop, as long as the irrigation water valve is off to the system.

If you would like to drain your backflow preventer, it would be best to open all of the test ports on your backflow preventer. Again, this may be accomplished by turning the test cocks 90° in either direction with a flathead screwdriver to open them.

The blue circled test cock on this RPZ backflow preventer is open & the black circled test cocks are closed
The blue circled test cock on this RPZ backflow preventer is open & the black circled test cocks are closed

Wilkins 375XL

A Wilkins or Zurn 375XL is another RPZ model. Wilkins 375XL backflow preventer also has four test cocks that can be drained in the same process. The test cocks on the 375XL backflow are just angled and located slightly differently.

The test cocks on this Wilkins 375XL RPZ backflow preventer are closed
The test cocks on this Wilkins 375XL RPZ backflow preventer are closed

The test ports in the photo of the Wilkins 375 RPZ are all closed. As with the 975XL RPZ, the test cocks can be slowly turned 90° in either direction to drain the water.

Here are photos of other RPZ models with labeled test cocks:

Watts 919

Test cocks labeled on a Watts 919
Test cocks labeled on a Watts 919

Febco 825Y

Febco 825Y
Febco 825Y

Febco 860

Febco 860
Febco 860

PVB (Sprinkler Pressure Vacuum Breaker)

This Febco 765 PVB has two test ports
This Febco 765 PVB has two test ports

Draining a pressure vacuum breaker, like a Febco 765 in the photo above, is very similar to draining an RPZ valve. A PVB pressure vacuum breaker assembly has two test ports, while an RPZ reduced pressure valve has four. So, you’ll need to drain two fewer backflow test cocks. What will you do with all of the time you have saved?!?

The test ports on this Wilkins 720A backflow are circled in red
Both test cocks on this Wilkins 720A backflow are closed

In the above photo of a Wilkins 720A pressure vacuum breaker, the red circle is highlighting the test cocks. Both test ports are closed in the photo.

You can open the backflow test cocks by inserting the flathead screwdriver into the test port valves and SLOWLY turning the bleeder valve either clockwise or counter-clockwise until you have eventually turned it 90°.

To start out the test cocks should look like the test ports in the photo of a Wilkins 720A pressure vacuum breaker below; but once you are done turning the test cock bleeder valves 90° to open them, they will look the opposite of the ones in the photo.

Both test cocks on this Wilkins 720A backflow are closed
Both test cocks on this Wilkins 720A backflow are closed

Spill Resistant Vacuum Breaker

It is less likely that you will need to drain your spill resistant SVB, because they are ideal for indoor use (they’re designed to not spill), and obviously most indoor spaces are heated. If preventing freeze damage is the reason you are draining your backflow, it is likely unnecessary in an indoor, heated space such as a basement or heated garage. 

But if you do need to drain your spill resistant vacuum breaker (SVB), here is a photo of the test cock:

Wilkins 460XL
Wilkins 460XL

Double Check

Much like an RPZ, a double check backflow preventer also has four test cocks. 

Febco 850
Febco 850

And just like an RPZ, each test cock can be turned with a flathead screwdriver to drain the backflow preventer.

Here is a photo of another double check model (Watts 719QT) with labeled test cocks:

Watts 719QT
Watts 719QT

Back Flow Valve

It may seem tempting to turn off the backflow preventer shut off valve, but this is probably not a good idea for now. If there is water in the backflow preventer, you want to provide a way for the water to flow out. If the backflow valve (or valves) is (are) closed, it can trap any remaining water inside the pipes or backflow preventer and it can increase the likelihood of freeze damage. 

Water expands as it freezes. In fact, water expands by over 9% when it freezes. This 9%+ expansion is what causes the pipes or backflow preventer to crack. 

Have you ever put a room temperature can of Coke or bottle of beer in the freezer to cool it down quickly, and then forgotten about it? If so, you know exactly what that extra 9% of volume causes….a mess. 

The Coke can or Corona bottle is designed with efficiency in mind; so when the liquid freezes and expands by an extra 9% that the bottle or can is not designed to hold, it cracks open under the growing pressure and leaves you with frozen or half frozen soda or beer all over your freezer.

If the backflow preventer valves are closed, they can constrict the water inside. But if you have already drained down the water in the pipes and backflow preventer and the valve is open, there should be some room for the water to expand if it does end up freezing and expanding. 

So, for that reason, you may want to leave the two ball valves on either end of the backflow open. This should allow some extra room in case any ice shows up to the backflow preventer party uninvited.

Check out the photo below of a Watts pressure vacuum breaker (PVB) with two open shut-off valves with blue arrows pointing to them. This is what you will want your ball valves to look like if you have a PVB:

The backflow valves on this PVB are open
The backflow valves on this PVB are open

You can tell the backflow valves are open because the back flow valve shut-off handle runs parallel with the pipe. Assuming that your irrigation system has been on for the warm watering season, your backflow valves should be on. If so, you can just leave them that way.

In the below photo of a Febco 765 pressure vacuum breaker, the shut-off valves are also open.

The backflow valves on this Febco 765 pressure vacuum breaker are open
The backflow valves on this Febco 765 pressure vacuum breaker are open

 If the backflow valve handle runs perpendicular with the backflow and pipe, that means it is closed. 

The photo below shows two closed shut-off backflow valves:

The backflow valves on this Wilkins 720A pressure vacuum breaker are closed
The backflow valves on this Wilkins 720A pressure vacuum breaker are closed

How to Remove Backflow Preventer

If you have an outdoor backflow preventer, rather than simply draining it, you might want to just disconnect it and bring it inside your garage or basement. This may or may not be possible. It will depend on whether your backflow preventer has what are called “unions” or not. See the photo below of unions on a Watts 009. Specifically, a Watts LF009. Even more specifically, a Watts backflow preventer 009 with unions.

Watts backflow preventer 009 with unions
Watts backflow preventer 009 with unions

Unions are the part that makes the backflow preventer (relatively) easily to be attached and reattached to the pipe connections each year. Unions are threaded fittings that connect both a male and a female part by screwing together. On a backflow preventer, unions are often attached around shut-off valves and allow the backflow preventer itself to be disconnected from the shut-off valve and the backflow pipe manifold.

If your backflow preventer does have unions, you can unscrew them to remove the backflow preventer; and then reattach them by screwing them back together. Much like removing the sprinkler blow out cap, you will likely also need your adjustable pliers or Channel Locks to get the process started. This is because backflow preventer unions can be difficult to turn. Moreso if your backflow preventer is outside because it is exposed to the elements (rain, wind, UV rays, heat, cold, snow, etc…).

Because the pipe and fittings that connect your backflow preventer to the water pipes are vulnerable to breaking, unscrewing the backflow preventer unions needs to be done extremely carefully, regardless of what kind of pipe your backflow is connected with. But if your backflow pipe connections are PVC or CPVC, then you really need to be careful

There are stronger versions of PVC pipe like schedule 40 and schedule 80 that are thick and tough and can withstand some abuse, however standard class 200 PVC pipe can break easily if it is wrenched or torqued too hard.

Wilkins 975XL with unions & shut off valves connected to PVC
Wilkins 975XL with unions & shut off valves connected to PVC

This is why it is very important to be careful and gentle when you are unscrewing the unions to remove your backflow preventer. You do not want to apply too much pressure and snap the pipe. I mean, isn’t the whole point of what we’re doing to avoid cracks in the pipe from freeze damage? Let’s not compound the potential problems by breaking your pipe in two before the temperatures even get down below freezing.

If you start to try to turn it and the union won’t budge, you may want to think about spraying some WD-40, or some other kind of penetrating oil lubricant to help loosen up the union. Then as the saying goes, try try again.

If the unions are stuck, another way to avoid damage is to apply counter pressure by holding the backflow preventer or or the pipe while you are turning the unions with your tongue and groove pliers. If your unions are fairly loosely connected it may not be necessary, but sometimes turning the unions requires a decent amount of force. In these cases, it is best to grip and brace the backflow preventer or backflow pipe while you are turning each union.

After successfully unscrewing the first union, you will need to hold onto the backflow preventer while unscrewing the second union anyway; because once the second union is unscrewed, the backflow preventer will fall on the ground if it is not being held. 

Removing your backflow preventer is the far easier part. Reconnecting it can be a hassle. It is possible that your irrigation company may charge extra to reconnect your backflow preventer. Most don’t, unless there are issues that make it a more time consuming process. 

But an RPZ backflow preventer can cost $1,000 or more to replace if it freezes and cracks; and they certainly shouldn’t be charging you anywhere near $1,000 to reconnect your backflow in the spring. So, don’t let a possible small backflow reconnection fee discourage you if you feel strongly that the backflow preventer should be removed and brought inside.

In the photo below, you can see the unions on a Wilkins 975. Specifically, a 975XL. Even more specifically, a 975XL backflow.

Wilkins Zurn 975XL with unions
Wilkins Zurn 975XL with unions

And here is a photo of unions on a Watts LF7. Specifically, a Watts LF7 backflow preventer.

Watts LF7 backflow preventer with unions
Watts LF7 backflow preventer with unions

The choice between draining or removing the backflow is yours. In many cases, turning off the irrigation system’s water shut-off valve and draining the backflow preventer will be sufficient to prevent freeze damage for a night or two. But, if you are concerned and you have a backflow preventer that has unions, you can take your backflow inside and remove any possibility that it will freeze after you drain sprinkler backflow preventer. 

Insulate Backflow Preventer

Once you have drained your backflow preventer, if you choose not to remove it for the winter, you can also insulate it to further prevent possible freeze damage. This may only raise the temperature of your pipes and backflow by a few degrees, but those few degrees could be the difference between a cracked, frozen backflow preventer that costs $1,000 to replace, and a non-cracked, frozen backflow preventer that does not cost you $1,000 to replace. 

To insulate your backflow valve, grab some old towels or blankets and wrap them around your backflow preventer and pipes. Then you may want to add some plastic bags and tape to make sure they don’t fall off if it gets windy or gravity rears its ugly head and the insulation falls off causing you to no longer have an insulated backflow preventer. 

Speaking of tape, you may be tempted to buy heated tape to wrap around your backflow valve, but you should know that once it has been applied, it is a huge hassle to get that tape off. Because it heats up and is adhesive, it basically bakes onto the backflow valve and the pipes. And removing it can take hours of scratching it off.

Regardless of which precautionary steps you choose to take, you now know how to turn off backflow valve. And knowing how to drain sprinkler backflow may just buy you some time and save you some money.

Abbreviated Instructions:

  1. Turn off the water shut-off valve to your irrigation system. See this article for additional details
  2. If you are uncertain whether or not you turned off the correct valve for your irrigation system, go to your controller or open the app on your smartphone and turn on your sprinkler system manually from your irrigation controller. If the sprinkler system does not come on, that probably means you turned off the correct shut-off valve. See this article for additional details.
  3. Turn on each zone from the sprinkler controller for a few minutes to try to allow gravity to drain some of the water in the pipes.
  4. Determine what type of backflow valve you have installed, and whether or not it has test cocks or unions and can be drained. See this article for additional details.
  5. Double check that you have turned off the correct sprinkler shut off valve, rather than your whole house water shut off valve. One way to do this is to turn on your main floor kitchen or bathroom sink and let it run for 20 seconds or more to see if the pressure starts to die down. If so, you probably accidentally turned off the whole house water shut off valve. So, turn it back on and keep looking so that you can turn off water to sprinkler system.
  6. Once you’ve found your irrigation system shut off valve, label your sprinkler system shut off valve so that future you knows exactly where it is.
  7. Get your flathead screwdriver ready.
  8. Drain your backflow preventer by SLOWLY turning the flathead-screwdriver-shaped bleeder valves on the top of each of your backflow preventer’s test cocks 90° in either direction.
  9. SLOWLY unscrew your sprinkler blow out cap/winterization point to drain even more water out of your backflow valve and any other exposed, above ground irrigation pipe that currently contains water.
  10. How to remove backflow preventer: If your backflow preventer has unions, you may consider unscrewing them (carefully!) and removing your backflow for the winter and storing it in your heated basement or garage to further reduce the possibility of freeze damage.
  11. If you choose not to remove your outdoor, above-ground backflow preventer, it can be beneficial to insulate it by wrapping it with old towels or blankets. You can then wrap them with plastic bags and tape it up. 
  12. Make sure to get your irrigation system fully blown out and winterized to remove the water from all of the sprinkler pipes before the ground freezes when it gets even colder

That’s it! You are now equipped with all of the information you should need to be able to drain your backflow preventer and buy yourself some time before your irrigation company can come out and winterize sprinkler system. 

I have tried to give you some side notes with helpful little tips and tricks. One was to be sure to label your irrigation shut-off valve so that you know where it is in the future. Another was to think about insulating your backflow preventer if you would prefer not to remove it for the winter.

I will leave you with one last bit of advice, and that is to go into your calendar for next year right now and add a reminder to contact your irrigation contractor in September or October at the latest to schedule your annual winterization service. That way you won’t be frantically googling “drain backflow preventer” at midnight on a very, very cold night. Instead, you’ll be fast asleep, or enjoying a delicious drink by the roaring fire in your warm, warm house.

Mistakes are inevitable, and they will continue to happen regardless of how cautious we are. But ideally we would try to learn from our errors and not make the very same mistakes year after year. So, whatever you need to do to make sure you remember to schedule irrigation winterization well before the temperatures get down below freezing, make it happen. 

If you keep a physical calendar and already have next year’s ready, write a note to yourself in September or October to schedule the sprinkler blowout. If you use Google calendar or Apple calendar, open it up and add an entry for September or October to schedule sprinkler winterization. Or you can think out of the box and tape a piece of paper to your rakes with a reminder to schedule sprinkler winterization. 

That way, when the leaves start to fall and the pumpkin spice starts to be added to everything, you’ll be sure to have a reminder. Or you could always take drastic action and go full Guy Pierce and write your sprinkler blowout reminders to yourself Memento-style…but that seems a little drastic. I’d stick with the calendar or note on the rake thing for now.

As always, thank you for reading! 

Good luck and be safe. 

  • Mister Irrigation

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