Can someone explain a vacuum relief valve on an irrigation system?

[bflynn]

I get what it's doing, it's like a reverse pressure relief valve. If there's a vacuum, water is going to be pushed backwards and that isn't good. But most importantly why do they suck at what they do?

After installing a whole house filter system, apparently the filter cannot supply water fast enough to the irrigation system. That creates low pressure and the valve opens. But it does have some pressure, so the valve starts dumping water. But in that state, it will never regain pressure because it's all going out the open valve.

Is something not right? Shouldn't there be some kind of reset so it doesn't perpetually waste water at a rate approaching Niagara Falls? It only ran for a couple of minutes, but it was measured at a rate of 14 GPM by a flow meter, which equates to 1.2 million gallons per day.

How is that not enough for the irrigation system?

 

[geezer]

Why are you irrigating with filtered water?

The irrigation system should come off the water supply ahead of the filter system, even if that is a lot of difficult plumbing.

Second, the valve may not be rated correctly or miss installed, for the described events to take place.

 

[172andyou]

Why are you irrigating with filtered water?

The irrigation system should come off the water supply ahead of the filter system, even if that is a lot of difficult plumbing.

Second, the valve may not be rated correctly or miss installed, for the described events to take place.

We filter because our well pulls up a fair amount of sand and would clog the sprinkler heads multiple times a summer if unfiltered. Maybe OP has something similar.

 

[Mahneuvers]

I don't know what a vacuum relief valve is. I was told I have a "back flow" relief valve on my system. I know it works b/c a fiber company, when I was out of town, not realizing I had a well reconnected county water to my irrigation system causing Niagara Falls as you say to spew out my well (almost $500 of water dumped in 2 days). My valve is installed after the filter. I'm sure this is stupid, but, might it be installed backwards?

 

[Skip Miller]

I don't know what a vacuum relief valve is. I was told I have a "back flow" relief valve on my system.

I think a backflow relief valve and a vacuum relief valve are the same thing, except the vacuum relief is likely to be more expensive as it sounds more exotic.

-Skip

@Mahneuvers

 

[Lindberg]

The vacuum breaker is supposed to let the water out from downstream of the valve even the incoming pressure drops. It may be dirty or you may need one for lower pressure. If it's not required by code, you could also replace it with a manual valve.

But the bigger question is why use filtered water for irrigation? That just going to cloud your filter much faster.

 

[Lindberg]

We filter because our well pulls up a fair amount of sand and would clog the sprinkler heads multiple times a summer if unfiltered. Maybe OP has something similar.

I'd rather use sprinklers designed for that, like rotors, rather than deal with filters.

 

[Mahneuvers]

...But the bigger question is why use filtered water for irrigation? That just going to cloud your filter much faster.

Same as @172andyou, for me, my well pulls up a good amount of sand etc. I have to backwash the filter every month or so. I have every imaginable kind of sprinkler head and even drip lines so I don't think I had a choice.

 

[172andyou]

I'd rather use sprinklers designed for that, like rotors, rather than deal with filters.

I mean, that's another way to solve the problem.

But since I filter and I'm cleaning the filter a couple times a year anyway...

 

[MauleSkinner]

Maybe you need a pressure pump between the filter and the vacuum breaker.

Ultimately, you probably need to talk to a professional, because we don’t have the answers here, apparently.

 

[PaulS]

You need a bigger or better filter. I had a strainer type filter that you could backwash as needed.

 

[Let'sgoflying!]

I would not use drinking water-level filtration to irrigate grass/trees/shrubs.

If sand is clogging the irrigation heads, consider taking water from your supply and plumbing in an appropriate filter for that; it's going to have much larger 'pores' than a drinking water filter. I have one for my trees, it looks like this:

IrrigationKing 2" Y Screen Filter – 120 Mesh, 110 GPM, 2" MNPT

The RKY225 is a 2" Y-style screen filter for commercial and agricultural irrigation mainlines. Its stainless steel mesh screen traps sediment and debris before it reaches drip emitters, sprinkler nozzles, or control valves. The compact Y-body installs inline with minimal headloss and the...

www.irrigationking.com

 

[172andyou]

I would not use drinking water-level filtration to irrigate grass/trees/shrubs.

If sand is clogging the irrigation heads, consider taking water from your supply and plumbing in an appropriate filter for that; it's going to have much larger 'pores' than a drinking water filter. I have one for my trees, it looks like this:

IrrigationKing 2" Y Screen Filter – 120 Mesh, 110 GPM, 2" MNPT

The RKY225 is a 2" Y-style screen filter for commercial and agricultural irrigation mainlines. Its stainless steel mesh screen traps sediment and debris before it reaches drip emitters, sprinkler nozzles, or control valves. The compact Y-body installs inline with minimal headloss and the...

www.irrigationking.com

That's fair. I basically have a whole house sediment filter for the sand and a drinking water filter for the fridge. I care that my shower doesn't get clogged by sand, but don't care if I can safely drink a half gallon a day from it.

Now, having had a whole house sediment filter and having not had one, that's definitely the way to go. I had one like you linked from irrigation king. And it did keep the drip lines from clogging. Did exactly zero, of course, for 12 taps at various places in the house. Once I realized that those problems were caused by the same problem I solved with the drip system, I put the whole house version in and haven't had to replace screens or rings anywhere in the house in 15 or more years.

 

[Sac Arrow]

I get what it's doing, it's like a reverse pressure relief valve. If there's a vacuum, water is going to be pushed backwards and that isn't good. But most importantly why do they suck at what they do?

After installing a whole house filter system, apparently the filter cannot supply water fast enough to the irrigation system. That creates low pressure and the valve opens. But it does have some pressure, so the valve starts dumping water. But in that state, it will never regain pressure because it's all going out the open valve.

Is something not right? Shouldn't there be some kind of reset so it doesn't perpetually waste water at a rate approaching Niagara Falls? It only ran for a couple of minutes, but it was measured at a rate of 14 GPM by a flow meter, which equates to 1.2 million gallons per day.

How is that not enough for the irrigation system?

A vacuum relief valve is not the same as a backflow preventer. Vacuum relief valves just do that - allow air to enter a pipeline so that a vacuum doesn't form. A backflow preventer is a fancy check valve, preventing water from entering the house (or clean side) in the event that the irrigation line has greater pressure than the source.

A filter is a constriction in the line, so it will lower the downstream pressure, slowing the irrigation flow. I don't understand what is meant by 'valve starts dumping water.' Are you saying water is dumping out of an open valve to the ground?

Depending on the type of backflow valve you are using, there may be water dumping out of the device. If there is a lot, there may not be enough pressure for the device to operate properly.

 

[bflynn]

When the pressure drops, the valve opens and water comes out of it, measuring 14 gallons / minute on the flow meter.

Is that a broken valve?

 

[bflynn]

Why are you irrigating with filtered water?

The irrigation system should come off the water supply ahead of the filter system, even if that is a lot of difficult plumbing.

Second, the valve may not be rated correctly or miss installed, for the described events to take place.

Because that's how it's plumbed.

Trying to get the plumber back out to connect it to the main, but he is unreliable at best. Right now I have to go bypass the filter to water the grass.

 

[Sac Arrow]

When the pressure drops, the valve opens and water comes out of it, measuring 14 gallons / minute on the flow meter.

Is that a broken valve?

Still not clear on what water stream you are talking about. Is that:

a) The water going to the irrigation system, or

b) Water dumping on the ground out of a valve, or

c) A combination of both

 

[bflynn]

The water comes from the outside cutoff to the filter system to the house. Right now the irrigation system is plumbed into the house side of the filter. When it comes on, the pressure drops, there's no water in the house, and the valve outside starts free flowing water.

 

[weilke]

When the pressure drops, the valve opens and water comes out of it, measuring 14 gallons / minute on the flow meter.

Is that a broken valve?

It appears to be.

A vacuum relief valve should not dump any water. Maybe a few drops once the line is pressurized. It appears that yours may be stuck in the open position.

 

[bflynn]

The valve is a Zurn 710. I've opened the top and the mechanical pieces inside don't appear to have problems, nothing binding, no leaking. Didn't expect anything, but had to look.

The valve still doesn't make sense to me. It's held shut by water pressure. When you lose pressure, it opens and has no chance to ever shut again because the amount of water coming out of it keeps the pressure low. Horrible design.

 

[Lindberg]

The valve is a Zurn 710. I've opened the top and the mechanical pieces inside don't appear to have problems, nothing binding, no leaking. Didn't expect anything, but had to look.

The valve still doesn't make sense to me. It's held shut by water pressure. When you lose pressure, it opens and has no chance to ever shut again because the amount of water coming out of it keeps the pressure low. Horrible design.

You may have sand in the valve preventing it from closing all the way. Or with the reduced pressure from the filter, the back pressure from your clogged sprinklers may be enough to keep it open.

 

[bflynn]

You may have sand in the valve preventing it from closing all the way. Or with the reduced pressure from the filter, the back pressure from your clogged sprinklers may be enough to keep it open.

No, it's clean inside. It doesn't reopen, it never closes.

 

[Lindberg]

No, it's clean inside. It doesn't reopen, it never closes.

There's a spring that holds the diaphragm closed and the air inlet open until there's sufficient pressure on the upstream side to seal the air inlet. Yours isn't sealing the air inlet, so water is coming out. If it's clean and all the parts are in good shape, then you don't have enough pressure on the incoming side the fully open the check backed valve and close the air inlet. You either need to increase the incoming pressure or get a backflow device that will work at lower pressure.

 

[Sac Arrow]

The valve isn't working right. It should take very little pressure to cause it to shut. Usually these things don't even have springs to hold the valve in the open position. Or, per Lindberg, you need a valve that will seal at a lower pressure. I suspect it may be assembled incorrectly inside.

 

[Lindberg]

The valve isn't working right. It should take very little pressure to cause it to shut. Usually these things don't even have springs to hold the valve in the open position. Or, per Lindberg, you need a valve that will seal at a lower pressure. I suspect it may be assembled incorrectly inside.

He said it was working before the filter was installed. So the valve is probably okay. But that valve only comes in 3/4 in or 1 in varieties. At 14 gallons per minute, that's very low pressure. The other clue is that when the sprinklers are running he loses all pressure for the house.

What about a pressure tank downstream from the sediment filter?

 

[tspear]

The test when I had my irrigation system installed was a minimum 35 PSI and rate of 60 or higher (I forget what the metric is, but I know 14 GPM is not even close). That can only run a single zone at a time.
14 GPM is way too low for most irrigation systems from what I had read online when I was considering doing a DIY system.

The solution when water pressure is too low is to install a large tank, with a dedicated high-pressure pump to run the irrigation system. You have to manage the sprinkler cycles to allow the tank to refill; or get a large enough tank that it does not matter. But it works (my brother in law has one, he went with multiple cycles and a tank large enough for a half run).

Tim

Edit: fix flow rate.

 

[Sac Arrow]

He said it was working before the filter was installed. So the valve is probably okay. But that valve only comes in 3/4 in or 1 in varieties. At 14 gallons per minute, that's very low pressure. The other clue is that when the sprinklers are running he loses all pressure for the house.

What about a pressure tank downstream from the sediment filter?

Is it? 14 gpm though a 1" valve is a fairly high velocity head, if his meter is reading correctly.

I'm not sure what effect a pressure tank would have, other than flattening out the transient pressures. An inline booster prior to the filters would work.

 

[bflynn]

It shouldn't have been plumbed into the house side to begin with. Plumber's mistake.

 

[brcase]

I'd rather use sprinklers designed for that, like rotors, rather than deal with filters.

My Sister has the same issue, the Sprinklers aren't the problem it is the Sprinkler Valves that can't handle the sand. After a about an hour of unfiltered water the Valve won't turn off.
She uses a separate Sprinkler system filter, but has to clean/dump it once a week.