· Plumbing
Backflow Preventer Replacement
Leaky Backflow Preventer and freezing temperatures don't mix.
Leaky Backflow Preventer and freezing temperatures don't mix.
Chapter 1: The back story
What happens when the inlet ball valve of your backflow preventer leaks, and you shutoff and drain said backflow preventer, and you let it go through the freezing winter? Yep...it breaks.
The trail of tears started when we noticed a GINORMOUS water bill for our sprinkler circuit.
I say "our sprinkler circuit" because our irrigation line is separate from our house line. That means we have two curb cocks, or shut-off valves at the city water connection. One for our house, and one for our sprinklers. This is handy so that when you need to do any irrigation supply repairs, you don't have to mess with your main house water supply. Anyways, I digress...
After getting this bill, we went on the search for a leak somewhere with the sprinkler lines themselves. After a few months of troubleshooting and not finding anything significant, we noticed some pretty heavy growth around the backflow preventer box. Even under normal circumstances, this isn't abnormal since our entire property pretty much drains into the locale where our backflow preventer resides. However, we noticed that it seemed a bit more than usual.
Our investigation revealed that there was a continuous leak coming out of the relief valve of the backflow preventer. However, the leak appeared to be emanating from this check valve. If you look closely, you can see that the check valve's seal ring (orange) is actually folded over itself inside the check valve assembly.
We inspected the check valves and the relief valve, and it was apparent that one of the check valves suffered some serious damage from the last freeze season, which was the cause of the leak.
So naturally, we did what you would expect any law abiding citizen to do, which is replace the parts that are damaged. Only replacing this simple spring and plunger assembly costs about $200. That was the best price I could find it. I still have no idea why these parts are so expensive. To buy the whole kit for all three valves it costs $500 - $600. OUTRAGEOUS!!!
So anyways, we bought the one kit, and replaced the front check valve. Tested it, everything looked good. At this time, we didn't need the circuit running, so I shut the inlet ball valve to prevent any water from entering the backflow preventer. Case closed...or so we thought.
A couple weeks later, we noticed even more overgrowth and a very unusual amount of mud. I lift the box covering the backflow preventer and find that there is a constant but faint stream of water coming out of one of the test cocks on the check valve. I had apparently left the test cock open after testing everything after the check valve repair. Which shouldn't have been a problem, except that there was an obvious additional issue with the inlet ball valve. Although I had shut off the ball valve, over time, it was opening up. And since I didn't have the test cock closed, water was constantly spewing out of it (face palm).
It was suddenly apparent what the root cause of check valve damage was. Although we had shut off the inlet ball valve during the winter months, it was also damaged enough to let water seep in and eventually freeze, then expand to the point where it deformed the check valve internals.
So now, the question was, can we replace the ball valve. It seems that it is attached to the check valve assembly, which denotes it should be detachable. We found that it was, but in order to replace it, we are looking at another $500 part, just for the inlet ball valve. I did find a cheaper alternative which was about $80, but it didn't have the test cock on it. The test cocks are handy and I use them (obviously, since I left one open) regularly, so I didn't want to replace the part without one.
So we decided to replace the whole part. After sourcing it, we found it for about $1,200. I didn't want to swap out the ball valve and find that we still need to replace the other check valve or the relief valve, or both, which would put me over the price of a new one. So we bit the bullet.
And so here we are which led us to this article that others may enjoy, and hopefully, it will help others see that anyone can fix there problems with the right tools, knowledge, and motivation.
Chapter 2: The plan
So we need to shut the water supply off at the street. Once that is done, then we can proceed to remove the backflow preventer and its connected elbows by unscrewing what are called unions. In our setup, the unions are just above the ground and are attached to the pipes which are coming out of the ground.
Chapter 3: I digress...test cocks are handy
Test cocks are handy for testing and draining the system.
Chapter 4: The removal
For some reason, the unions were installed in the inverse direction. The one on our side (the customer side), the union is installed right side up, and the one on the city side is installed upside down. That means in order to remove detach at the unions, we need to turn counter-clockwise on the customer side, and clockwise on the city side. Typically, you would turn both sides counter-clockwise to detach them.
Once the unions are detached, we can remove the backflow preventer and its elbows.
Chapter 5: Disassembly
The elbows are hand tightened to the backflow preventer, so they can be removed by hand. The disassembly consists of removing each elbow, and then cleaning up the threads on each of the elbows. We don't need to clean up the threads on the old backflow preventer since we are replacing it with a new one.
Chapter 6: Test fit with extender
After assembling our extender, we perform a quick test fit to ensure that we get the correct overall length so that our new backflow preventer assembled with the elbows, will fit in place on site.
Here is a bit more detail on our extender:
Chapter 7: Assembly
Assembly is just a matter of screwing the elbows back to the new backflow preventer with the new addition of our extender to compensate for the size difference between the old and the new one. The idea here is to get back to 31" on-center between the inlet and outlet. We get close enough with our assembly for a fit check.
The process of applying the pipe dope and the teflon tape is simple. We liberally apply the pipe dope to fill the thread gaps, then wrap that with teflon tape, being careful not to let the teflon tape cover the opening. Usually you can avoid this by starting the application of the teflon tape 1 to 2 threads back from the opening so that the tape doesn't breach the opening.
Once the teflon tape is applied, you simply screw the piece on with good old fashioned elbow grease. No tools required.
Chapter 8: Field test fit
This part was pretty easy. It wasn't exactly the fit I was expecting, but that was mainly because I was able to tighten the pieces more after putting the pipe dope and teflon tape on the threads. While a bit counter-intuitive, applying the pipe dope and teflon tape actually allow you to cover more threads when tightening, than when the parts are dry. It actually makes sense if you stop and think about it, but it isn't inherently obvious that you can tighten more after applying the thread sealants. Definitely something to consider when doing a dry test fit. I think the dry test fit was about a quarter of an inch wider than where we ended up after doing the final assembly. So be sure to compensate a bit of extra distance when using your dry test fit for measurement.
Chapter 9: Failure
It wouldn't be a DIY project without at least one failure. But if failure keeps you from doing-it-yourself, then you probably shouldn't be doing it. In short, my makeshift extension piece didn't perform how we needed it to. So, time to go to plan B, and source parts that are more fit for the function. Let's see what we find.
Chapter 10: Plan B
After running around town to three different hardware/plumbing supply stores, I found the combination of parts that I should have been able to find at Home Depot...at least it seems like I should have. But the short story is that Plan B consisted of two parts, a male threaded nipple, and a female threaded coupler. A nipple is simply a coupler that is designed to fit inside the standard set of pipe sizes. In other words, a 2" male threaded nipple, is a pipe that is covered in threads, that is meant to fit into a 2" female threaded coupler. It's classified as a nipple because it is setup the same on both ends, which in this case is male threads.
I connect this male threaded nipple, which is as short as the threads that cover it, to a female threaded coupler, which also has threads on both sides. We need threads on both sides of the female coupler, since it is attached to the elbow which has male threads. Putting these two pieces together, the threaded male nipple, and the female threaded coupler, gave us exactly the width we needed for our extension. So we put them together and attached the new extension to our whole assembly.
Chapter 11: Success
And there you have it, all pieces fit nice and snug, and the assembly is put in place without any leaks. After having the city water turned back on, we were able to activate without issue and we are now back in business.
For this unit, and in general, I think the activation procedure is similar. You start off with the inlet and outlet ball valves closed. Once the city water is turned on, follow these steps:
- Bleed any air in the circuit by opening the inlet ball valve test cock and wait for a constant stream of water without air. (Air sounds like a sprinkler when it is first turned on as it spits both water and air. Water without air is a constant steady sound)
- Close the test cock after bleeding the air.
- Slowly open the inlet ball valve (large lever on the city side)
- This lets water into the backflow preventer, but not into your system yet.
- Water will spit out the relief valve at the bottom, but should stop by the time you open it all the way. If it doesn't you may have a problem with the internals.
- Bleed any air in the backflow preventer
- Just as in the first test cock, open all other test cocks on the backflow preventer that are not attached to the inlet ball valve, and wait for the air to bleed out.
- Close the test cocks after bleeding the air.
- Now the unit is charged, and you can slowly open the outlet ball valve (the other large lever on the customer side).
And that's it. A successful backflow preventer replacement.
Conclusion
Thanks for following along in our journey as We DIY life around here. You can too. If you have any questions about what we did, how we did it, or other projects you might like to see, drop us a line using our Support Us link.