Backflow Preventer

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If it's intermittently dumping, then its more likely that there are surges or drops in pressure either before or after the check valve that are causing it to DO ITS JOB BY VENTING AND NOT ALLOWING PRESSURE TO BE HIGHER ON HIS SIDE THAN THE CITY'S.
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If you have a check valve before the BFP, then the lower pressure on the city side will not transfer into the BFP.

If you have a check valve after the BFP, that will isolate the BFP from spikes from sudden water hammer from a valve closing fast.
 
JamesW said:
If you have a check valve before the BFP, then the lower pressure on the city side will not transfer into the BFP.

If you have a check valve after the BFP, that will isolate the BFP from spikes from sudden water hammer from a valve closing fast.
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My buddy won't weigh in on that idea, as he emailed me that bit and I pasted it here. He's not a TFP member.

But I was comparing @JamesW's earlier suggestion about this with my buddy's explanation, and it struck me that the existing valve already has a check valve on the city side and another on the pool side, just as James is suggesting. I can't wrap my head around how adding two more, an additional one on each side, is going to help. But then, I don't really know much about how they work internally.

Now if the venting is being caused by the BFP "doing its job by venting and not allowing pressure to be higher on his [pool] side than the city's," maybe I can take a stab at what's going on. Let's say the auto-fill engages while there is no water use inside the house. Full pressure all around, and on both sides of the BFP. Then the pool tops off and the auto-fill closes. Now you've got full pressure "trapped" on the pool side of the BFP. And full pressure trapped on the city side, too. There should be no venting at that point. Then someone flushes a toilet in the house, and the pressure drops on the house/city side of the BFP. That would cause the venting my buddy is describing, because when the toilet flushes, the pressure on the pool side is higher than the pressure on the city side. It doesn't flow backward from the pool side to the city side, because that's what the BFP is preventing. So it vents instead.

Which why it's testing "good," because it's doing what it's supposed to be doing. It sounds like the issue isn't the BFP, but rather the property is just not supplied with enough water pressure to keep water use in the house from triggering the BFP venting. As my buddy pointed out, yes it's venting, but really it's just equalizing the pressure on each side the only way it can.

If the BFP is not dripping when the auto-fill valve is closed and there is no water use in the house, then doesn't that mean you don't have a leaking seal? If it only vents when the auto-fill valve is closed and someone uses water in the house, then I think that means it's fine, as it's doing what it's supposed to be doing. The only real solution is to increase the pressure on the city side, so that when you use water in the house, the pressure drop isn't enough to trigger the BFP venting. Which you can't do. So...

Put a receptacle under the BFP to collect the vented water, and periodically toss it on a plant or into the pool, where it can do some good, and call it a day. Use a plastic soda bottle instead of a bucket or pan to minimize evaporation in between dumping.
 
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There's another possible fix. Put a pressure regulator on the city side of the BFP. Dial it down pretty low. When the auto-fill closes and traps pressure on the pool side of the BFP, it'll be at a greatly reduced PSI. If you then use a toilet and the pressure drops on the city side of the BFP, that pressure drop on the city side won't be lower than the pressure trapped in between the BFP and the auto-fill valve, so the BFP won't need to vent.

But that's a pretty expensive experiment, and even if it worked, how much would you save in water costs if the BFP never vented again? It'd be years before you got a ROI on that pressure regulator (or James' check valves), maybe decades. That's why the soda bottle is your best bet. I'm thinking that's about 5¢ worth of a missed recycling refund! It'll save you some water (if you dump it into the pool), and allow the BFP to work as intended, and the auto-fill valve to fill your pool at the best flow rate available.
 
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Dirk said:
There's another possible fix. Put a pressure regulator on the city side of the BFP. Dial it down pretty low. When the auto-fill closes and traps pressure on the pool side of the BFP, it'll be at a greatly reduced PSI. If you then use a toilet and the pressure drops on the city side of the BFP, that pressure drop on the city side won't be lower than the pressure trapped in between the BFP and the auto-fill valve, so the BFP won't need to vent.

But that's a pretty expensive experiment, and even if it worked, how much would you save in water costs if the BFP never vented again? It'd be years before you got a ROI on that pressure regulator (or James' check valves), maybe decades. That's why the soda bottle is your best bet. I'm thinking that's about 5¢ worth of a missed recycling refund! It'll save you some water (if you dump it into the pool), and allow the BFP to work as intended, and the auto-fill valve to fill your pool at the best flow rate available.
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Come on @Dirk you and i both know the solution is all of the above! Add the pressure regulator before the backflow, then the automation valve followed by a drain under the backflow that attaches to the deck drains directed to a storage well with a pump for grey water irrigation usage 🤪🤣😜
 
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Dirk said:
Wow, lots to unpack. I'm not sure on which municipality you're basing these "facts," but I can say with some confidence they are not universal truths. I shouldn't guess on the percentage, but I'll go out on a limb and say most residential properties have no such BFP protection, and it's not built into water meters, if that's what you were getting at (I've never heard of that, anyway).

And based on that, it is not unreasonable at all for a municipality to require BFP devices. In fact, they are already a requirement for commercial buildings in many (if not most) cities. I'm referring to California, so I can't speak to the rest of the country. Obviously the OP's city is all over this, too. This is nothing like the seat belt law, which for the most part is intended to protect people too, uh, unwise to protect themselves. No, a requirement for a BFP has much less to do with protecting the individual's water supply, and everything to do with protecting the water supply of his neighbors, possibly for miles around. And, IMO, that is exactly what government is supposed to be doing.

Again, depending on where you live, it's not at all fair to say that a municipal water supply is less safe for humans than the water in a swimming pool. Many (most?) municipalities provide annual water quality reports, but I know from my buddy (who worked at the water provider for one of CA's largest cities) that these water quality tests go on constantly, non-stop. And from his description of them, no pool would pass 'em. He also believes that it is just a matter of time before it is a requirement for all residences to have BFPs, just like it is now for commercial properties. He figures they'll start with new construction. Not sure how they'd handle existing residences. But that's how I know it is not a given that residences or water meters have BFPs, because they mostly don't.


I'm not sure what point you're making about a "cheap hunter valve" closing. The type of auto-fill valve the OP has is closed most of the time. It opens when the pool's water level drops. The valve is underwater, somewhere near the pool, and so has no "natural" anti-siphon protection afforded when a valve's outlet is above the waterline. So that's why the need for the BFP upstream of it.

While that auto-fill vale is closed, it's under pressure, and many times (most?) the water line supplying that valve is before the home's pressure regulator, which means it can conceivably be under a lot of pressure. If you put a sprinkler valve upstream of that auto-fill valve, instead of a proper pressure-rated BFP, then that full-on water pressure is constantly applied to the sprinkler valve's anti-siphon components (springs and diaphragms and what not) that are not rated to withstand that level of pressure 24/7. And they will eventually fail. There's a reason a plastic Orbit sprinkler valve costs 17 bucks, and the OP's BFP valve is north of $500 and constructed of brass.

Think about it, those sprinkler valve anti-siphon components are virtually never under real pressure. Their subjected to any at all only when the sprinkler valve is open, and the water is flowing out the other side to sprinklers. Anyway, the point is, a sprinkler valve upstream of that auto-fill valve is not the correct application. And as I mentioned, it can't be tested, so you'd never know if the anti-siphon (BFP) protection was working or not. The fact that you might have had an arrangement like that that is still working proves nothing, and is not the kind of anecdotal advice that is OK to share with the many people that might read this thread (not just the few of us that are contributing to it).

And if you're describing a setup that has a non-pressure rated sprinkler valve upstream of a secondary tier of sprinkler valves, that would also violate the same safety standards. Just because you've seen it somewhere, even many times, doesn't make it OK.

And of course, all of this is otherwise moot, because the OP's city requires the correct part and for it to be inspected. Replacing that part with a sprinkler valve would not only not be a good idea, or safe, but it's not allowed in the OP's case. Which is what inspired my original rebut to your post.

So, again, pardon me for the push back. As I mentioned, I learned all this from a pro that worked for decades at a major municipality in California. He was personally responsible for testing commercial property BFP valves all over the city. The rest of the time he spent monitoring the water quality at the plant that supplied the water to about a million people. I trust what he told me.
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For 45 years, every house I've lived in, rented, or owned, in 4 states has had a DC at the meter, provided by the WSC. I can;t beleive that several of those backwater states are more proactive than California on a natural resource, but I do find that comical.

And that aspect alone was why I mentioned seat belt laws. The supply is already protected. Not putting on one your pool (which uses a float valve in a pot/reservoir, which have an air gap inherent in their design, and prevents siphoning) isn't protecting the supply, so much as your home system.

The natural solution to all these laws if you just want an automated solution is to plumb a fill line into the skimmer basket well above the waterline, and use an automated actuator (or simple sprinkler valve) to do so. It's the cheapest option short of a ball valve, doesn't backflow in any way, and can be automated for less than $30. But I guarantee your city inspector will still require a BFP because its a "pool fill line" and government is mostly worthless and incapable of rationality.
 
If the pressure is 60 psi before the valve and after the valve, then it won't vent.

If the pressure at the supply side goes to 55 psi, then it will vent.

However, if you have a check valve, the pressure before the valve is still 60 psi.

Also, the manufacturer recommended it and you would think that they should know.

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Alex_K said:
For 45 years, every house I've lived in, rented, or owned, in 4 states has had a DC at the meter, provided by the WSC. I can;t beleive that several of those backwater states are more proactive than California on a natural resource, but I do find that comical.

And that aspect alone was why I mentioned seat belt laws. The supply is already protected. Not putting on one your pool (which uses a float valve in a pot/reservoir, which have an air gap inherent in their design, and prevents siphoning) isn't protecting the supply, so much as your home system.

The natural solution to all these laws if you just want an automated solution is to plumb a fill line into the skimmer basket well above the waterline, and use an automated actuator (or simple sprinkler valve) to do so. It's the cheapest option short of a ball valve, doesn't backflow in any way, and can be automated for less than $30. But I guarantee your city inspector will still require a BFP because its a "pool fill line" and government is mostly worthless and incapable of rationality.
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OK, gotta correct you again, though not so sorry this third time. You're assuming all residences are just like the ones you lived in (they're not) and that all auto-fill mechanisms are the same (they're not) and that you know what auto-fill means (you don't seem to).

Yes, you can automate with a timer and a sprinkler valve the filling of your pool, but (a) that's not the kind of auto-filling we're talking about, and (2) you can't outlet that into the skimmer and call it "safe" because that would assume a pool has any sort of overflow protection which isn't the case in all pools. So if you've got a fill line outleting into the skimmer well, that's not a reliable air gap because a storm could overflow the pool and so submerge the end of the fill line. To give that kind of setup a proper air gap, it would need to be many inches above the coping (they used to be that way, typically a copper L-shaped pipe sticking up out of the coping under the diving board, but they don't do it that way anymore). And that kind of setup, if properly air-gapped, would not need a pressure-rated BFP and would work just fine with a sprinkler valve, because there would be no second valve downstream of it. But that's not what the OP is working with, so your "solution" is not applicable to his setup and doesn't solve his problem.

The kind of auto-fillers I'm referring to, when I talk about the "second valve downstream" are the type that are submerged underwater in some sort of reservoir, typically a foot or two from the pool, and react automatically to the level of the pool water (they're not on a timer). They contain some sort of float valve. Some, like the OP's, are a simple lever, others are pretty much toilet tank valves. The toilet tank variety provide no air gap. I'm not sure if the lever type provides one or not, I don't think so, but either way their outlet would be below the level of the coping, so have the same inherent problem as your "hole in the skimmer" idea: they don't provide a proper, safe air gap under all conditions, and so require a pressure-rated BFP somewhere between the auto-fill valve and the city water supply, which is what the OP is dealing with.

I agree with you, that if you already have a decent BFP somewhere after your water meter, and maintain it properly, that that should be sufficient protection. Not all properties do. I don't think the OP mentioned he had one of those, and I haven't assumed he does. And in that case, his municipality requiring a BFP for the auto-fill valve he possesses is totally legit, and not at all any sort of government overreach or ignorant, unnecessary code. It's a responsible requirement that helps protect his and his neighbor's water supply.

It'd be great if everyone and their pool builder did the right thing in that regard, and thoroughly understood how a pool's auto-filling mechanism can threaten a water supply, and so used all the proper components, installed them correctly, and kept them all well maintained. But that, you've demonstrated, is not the case, and so municipal codes exist for good reason.
 
JamesW said:
If the pressure is 60 psi before the valve and after the valve, then it won't vent.

If the pressure at the supply side goes to 55 psi, then it will vent.

However, if you have a check valve, the pressure before the valve is still 60 psi.

Also, the manufacturer recommended it and you would think that they should know.

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OK, I understand how a check valve before the BFP would solve for the pressure differential. I don't understand how the existing check valve inside the BFP valve isn't performing that function, but that's OK. And I didn't know a BFP valve is supposed to have another check valve in front of it. How would that extra check be tested/maintained? Would an annual test of the BFP valve reveal a malfunction is that pre-BFP check? Can you point me to documentation about that manufacture recommendation? I'd like to learn about that.

One of us is missing something here (me, probably). If a BFP is designed to equalize the pressure differential on each side of it (as my buddy describes), how would circumventing that function with a check valve or two be a good thing? That's where I'm getting lost. If a couple of extra check valves are necessary, why would you need the BFP at all? The check valve(s) would keep pool water from reaching the city's supply, wouldn't it? (Though they wouldn't be testable, unless some exist that are). Pardon my boneheadedness...
 
@jimbethesda, pardon this deep dive into the whats-its of backflow prevention, but this is sometimes our process here at TFP, to get to the bottom of things. Especially in the winter when we're slow and it's raining and we can't go outside and play!!

I hope you're finding some of this useful...
 
jimbethesda said:
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".
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Dirk said:
Can you point me to documentation about that manufacture recommendation?
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Dirk said:
If a BFP is designed to equalize the pressure differential on each side of it (as my buddy describes), how would circumventing that function with a check valve or two be a good thing?
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You're not circumventing the BFP.

It still works as intended.
Dirk said:
That's where I'm getting lost. If a couple of extra check valves are necessary, why would you need the BFP at all?
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You still need a certified BFP because a check valve is not a certified BFP even though it does prevent backflow.
Dirk said:
The check valve(s) would keep pool water from reaching the city's supply, wouldn't it?
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Yes, but they are not certified as BFPs.

The BFP includes antisiphon, which the check valve does not have.

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