Backflow Preventer

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jimbethesda

jimbethesda

Gold Supporter
Jul 2, 2018
648
Austin, TX
Pool Size
20000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
The city requires a back flow preventer be hooked up to my autofill line. The pool builder installed one. The problem is that, fairly often, it starts to vent water from the CITY side. I know it's from the city, because I tasted it (not salty at all) and also my pool water level was well below the autoflow so no way it could be from the pool.

I called someone and said that I think it's installed backwards. Why would you ever want to vent out the city water? Isn't this suppose to ensure that pool water doesn't end up in the water supply? I'm ok with city water going into the pool (that's why I have the autofill).

So...I've turned off my autofill. I was tired of listening to our constant wasting of water.

My question is, is this true? Is this really how they are designed, or do I have a bad one? If it is how they are designed, any engineers want to start a back flow preventer business?

Thanks.
 
Here's a picture. Looks like the brand is Wilkins Zurn. Not sure where the model name is.


IMG_0493.jpeg
 
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Which way is the water going?

How old is it?

When did the problem begin?

img_0493-jpeg.476339

1678312567956.png
 
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JamesW said:
Which way is the water going?

How old is it?

When did the problem begin?

img_0493-jpeg.476339

View attachment 476343
Click to expand...
The water from the city is the pipe on the right, pipe on the left goes to the pool. That seems to match the picture you posted.

It was installed 4 years ago. I noticed the issue soon after it was installed. It doesn't vent all the time, so it took me a little bit to notice. My best guess is that it's always done it. I stopped using it about 2 years ago. I'd either like to get rid of my autoflow altogether so I don't have to have it inspected every year. If I can get it to work better, that's even better.

Thanks.
 
James beat me to it. They have arrows on them indicating which way the water should flow. So that's easy to determine. Start there.

I have seen mine spit water once is a while, but it's like a teaspoon or so, it's not a constant flow or anything like that.

The nice thing about having a quality BFP is that it can be tested. These are the test ports:

Screen Shot 2023-03-08 at 2.10.48 PM.png

Someone with the proper equipment uses these ports to verify the thing is working as it should. The trick is in finding that "someone." The guy that tests mine once in a while used to work for a big city's water company. Start there. Call your local water company and see if they offer BFP testing, either free or for a fee. If not, see if they can recommend someone that can do it.
 
Dirk said:
James beat me to it. They have arrows on them indicating which way the water should flow. So that's easy to determine. Start there.

I have seen mine spit water once is a while, but it's like a teaspoon or so, it's not a constant flow or anything like that.

The nice thing about having a quality BFP is that it can be tested. These are the test ports:

View attachment 476347

Someone with the proper equipment uses these ports to verify the thing is working as it should. The trick is in finding that "someone." The guy that tests mine once in a while used to work for a big city's water company. Start there. Call your local water company and see if they offer BFP testing, either free or for a fee. If not, see if they can recommend someone that can do it.
Click to expand...
It's tested every year, actually came out today which prompted me to post this. Every time they say, it passed and is working as designed. Either they are wrong, or all back flow preventers are designed poorly. Or maybe I'm just missing something?
 

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JamesW said:
It has a vent, so it must vent for some purpose, but I am not sure what causes it to vent.

I would contact the company and ask them if the operation is normal or not.





Contact Us | Engineered Water Solutions | Zurn

Call Zurn Customer Support at 1-855-ONE-ZURN (1-855-663-9876), or by filling out our contact form here.
www.zurn.com www.zurn.com
Click to expand...
I watched the troubleshooting video already. He talks about troubleshooting venting from the POOL (or other application) side. Never once did he mention troubleshooting why it's venting from the city side. I'll reach out to the company.
 
I called them. He defended why it's designed this way, but said that if it is discharging a lot and seems to do it when we use water (toilet flush, start shower, etc.), then a single check valve installed before the back flow preventer should help and take the brunt of the "water hammer".

Does that sound right? I'm happy to spend the money for a plumber to install one, but only if it will work.

Thanks for all your help.
 
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It seems logical to me that installing a check valve before and after the backflow preventer would reduce discharge.

You can also do a rebuild as shown in the video to make sure that the issue is not related to worn, damaged or defective parts.

Maybe put a pressure gauge on your supply plumbing somewhere to see what the normal pressure is and if it is fluctuating a lot.

You can install it on an outside spigot and watch the normal pressure vs. pressure drop during high use.




 
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What is between the discharge side of the BFP and the pool ? Can you sketch what that plumbing looks like?
 
If they don't require specific BFP in language that would warrant a $200 model like that WZ, go to Home Depot and pick you up a Orbit or Hunter model from the sprinkler aisle and replace it. Usually to see that much brass it's because the city requires a double check rather than just a simple backflow preventer. With the money you save, you can pick up a sprinkler valve and wire it into the 24V on your automation and have it only pressurize for X hours per day in the middle of the night or whatever.

BFP for pools amuse me as its a government response to a non-problem that costs us all. Your chlorination in the pool is far higher than what the city keeps :)
 
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Possible that it's trying to warn you of a different issue. My irrigation bfp did this after the pressure regulator on our house died(i ignored other symptons like failing toilet valves and awesome showers lol). The excess pressure in the house created a hammer forcing water into the backflow which was then stopped by the closed sprinkler valve. This sent water back to the backflow which then discharged the same water as it can only go one way.
Not sure if I explained that in a competent way lol but bottom line, check the pressure in the house to see if the pressure regulator is working which could be the actual issue. Our water district requires the full rpz at the street to protect the city, an rpz at the irrigation and and rpz at the pool. This creates a closed system so combined with unusually high pressure causes drama.

As an additional note , I installed several pressure guages all over now to watch for this.
1. After rpz at the meter
2. After pressure regulator for the house
3. After water softener inside
4. Before pool rpz
5. After pool rpz and pool pressure regulator
 
Alex_K said:
If they don't require specific BFP in language that would warrant a $200 model like that WZ, go to Home Depot and pick you up a Orbit or Hunter model from the sprinkler aisle and replace it. Usually to see that much brass it's because the city requires a double check rather than just a simple backflow preventer. With the money you save, you can pick up a sprinkler valve and wire it into the 24V on your automation and have it only pressurize for X hours per day in the middle of the night or whatever.

BFP for pools amuse me as its a government response to a non-problem that costs us all. Your chlorination in the pool is far higher than what the city keeps :)
Click to expand...
Alex, I hope you don't mind me correcting you a bit. There is a lot more than chlorine in a residential swimming pool, and it's definitely not potable water. If a backflow event occurred, pool water could contaminate an entire neighborhood's water supply, rendering it unusable, and creating a costly cleanup. It's conceivable the pool owner could be held liable for damages, too.

And a sprinkler valve is not appropriate, at all, for this application, because they are not rated to have a second valve downstream of them (only wide-open sprinklers or drip systems, that drain when they're done). The auto-fill valve at the OP's pool is that second valve, and even if he used a timer to shut off the sprinkler valve, the pool side of the sprinkler valve would remain under constant pressure, eventually causing it to fail as a backflow preventer, and very likely without him realizing it. Plus, there is no reliable way to test the BFP function of a sprinkler valve.

The reasons a municipality might require a proper BFP valve for a pool fill system are legit.

He's got the right part for the job, he just needs to determine if it's functioning correctly.
 
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