I have two (hopefully small) repairs that I need to do for my system. Luckily most of it is in a control box, so it is easy to get at. Here's the setup:

Sprinkler setup

At the top was a valve that was broken, and at the bottom was (what the guy Lowe's said was) a backflow preventer:

Backflow preventer angle 1Backflow preventer angle 2

Last relevant picture, is just outside of the control box on the left side:

Outside the control box

It's still a little covered, but you can see that there is a T joint close to the box.

Replacing the valve

The valve that was in place had male connectors, but the store only had valves with female connectors. I bought one of those valves and two adapters, but there isn't quite enough room - the valve plus the two adapters is about 2cm too wide to fit. These are 1" pipes. The two parts to connect to are swivel connectors somewhat like this.

What are my options here? I thought of three possibilities, and would like to know which one would work best as a long-term fix and if there is a better option that I haven't considered.

  1. Cut off about 1 cm from each of the two adapters until the valve+adapters fits snuggly in there. This should leave a little more than 1 cm exposed on each side. I'm concerned that this wouldn't leave enough to screw onto to get a good seal. I also don't trust my ability to cut the adapters cleanly enough to have it be absolutely flat against the other parts of the pipe.

  2. Cut off one of the swivel connectors and put a new one on. I could cut off enough pipe to get a fit as snug as I need and also get slightly longer adapters to make sure that the fit isn't too loose.

  3. Cut out a section of pipe and get a connector to rejoin the two new ends, effectively shortening the pipe.

General question - how tight does the fit need to be? Will it leak if there is even a small gap between the adapter and the pipe inside of the swivel connector?

Replacing the backflow preventer

As you can see in the pictures, there was an adapter at the end of the pipe coming into the box, but it was cracked and the threaded part came off with the backflow preventer (which was also cracked, hence why I needed to replace it). After I cut off that broken adapter there will still be 1" of pipe coming out of the T joint. There will be 6" of space from there to the threading of the valve that's still in there. Here I'm working with 3/4" pipe. I already have a new backflow preventer with female connectors on both ends, and it's not quite 5" long.

How do I replace this? There's not enough room in there for an extendable repair piece. I figure that I should put the new backflow preventer in first, and that will leave about 1.5-2" of space and then 1" of pipe to connect to. What parts should I get and how to I get them all in there?

2 Answers 2


Well, I think you have some remodeling of your sprinkler system to do. Here are some things that you need to think about.

  1. There needs to be an anti-siphon type valve on each controlled sprinkler circuit.
  2. These anti-siphon valves need to be mounted at an elevation that is 6 to 12 inches above the highest level of the sprinkler heads on each circuit. Not in a box buried under the ground.
  3. Since all of the controlled valves will feed off of the same pressurized main water line it is convenient to install all of the valves at the same elevation.
  4. If you want to hide the valves then build a wood cover that is above grade to hide then and blend in with the side of the building structure.

So if you understand the above most of your questions become moot. Pull that box of the ground and toss it away. Then re-pipe the main water feed line to above grade and create a manifold arrangement that can feed to the number of anti-siphon valves that you need (number of controlled sprinkler circuits). The manifold is best placed closer toward the building foundation. Then re-pipe the various sprinkler circuit pipes so that come up right in front of the manifold connections. The valves will affix above. When it is completed it can look something like this:

enter image description here

or like this:

enter image description here

The advantages are many. It is much easier to repair and replace things that you can get to. The anti-siphon type valve, properly deployed, is the tried and true method to provide the isolation between the pressurized potable water service and sprinker circuits. Placing your control valves high like this is also an advantage if you live in a freeze climate zone where it becomes necessary to use pressurized air purging of the lines to clear out all the water before winter. The air can be applied to each circuit at the control valve. Lastly your low voltage control wiring is above grade where is stays much dryer and less chance of wiring corrosion.

  • 2
    I agree with the anti syphon idea but I lived in a city that required backflow preventers on all in ground sprinkler systems and they were required to be tested every 2-3 years. This was all that was required so a total redo may not be required but a good idea.
    – Ed Beal
    Commented Aug 25, 2017 at 19:12

I guess my take on this one would be to dig up the box and replace the whole thing. You're gonna need to dig out those pipes and get rid of that tee with a one inch lead. You'll maybe get a coupler to stay, it might leak. Tees also cause friction in the line. So if you're going from main water to back flow and then tee off immediately and go different directions, just a lot of turns and twists in a short distance. Dig this up, put in a bigger box so you have more room;dig down deep enough you can fill the bottom two inches of the box with gravel, leave the pipes exposed and a couple inches above that and replace your back flow. And move that tee a foot down the line so you'll have less restrictions. I know they say with pvc and poly it doesn't matter; it does. I been digging trenches for thirty years. I've seen it all.

That other guy's setup is righteous but I imagine it'd cost a fortune. I'm in Minnesota and I've not seen it done here like that but I wouldn't be surprised if that's the way we end up going. I'd probably buy a giant fake rock to cover all that because I find plumbing unsightly but that's just me.

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