Plumbers STUMPED!! Sprinklers causing Airlock in Hot Water tank

[shadowstar57]

Hello, I've had a couple of plumbers out here, and they left in defeat, stumped as to what is going on:

Every morning after the sprinkler runs, we have no hot water in the house (no drips, no noise, just nothing coming out of faucet). Cold water is fine. After much research in the forums, I narrowed it down to an airlock being created in hot water line (or electric HW tank) after the sprinklers turn on or off. Reason being, after I open up all the hot water outlets in the house for a while (sometimes hours), the hot water will suddenly 'pop' out and start flowing again.

I've got a 6 zone system, but only use 4 zones. Automatic controller. Run them for only about 5 minutes now everyday around 3:30am, one zone per day (2 zones on 2 days a week). Yesterday I tried closing the sprinkler's shut off valve about 50% to reduce the pressure, but no noticeable change. There's no hot water coming out of sprinklers.

Any ideas what could be going on here? Thanks for your help!

 

[Reach4]

When you have the problem, what pressure do you have at the WH drain valve? Those drain valves have a garden hose thread. You could get a screw-on pressure gauge, or you could just open the valve. You could hook a garden hose to that valve and open the valve to observe the flow. A pressure gauge would be under $20. Checking the pressure at the WH will determine if the problem is before the WH or after.

Well or city water? Do you have a hot water recirculation system?

That "airlock" for your water heater... I doubt there is such a thing. Sounds to me as if some check valve or mixing valve is sticking somehow.

 

[Sponsor]

 

[hj]

The ONLY way an "airlock" could occur is if you "pumped" air into the water lines. It CANNOT get in there accidentally. Your diagnosis is faulty, and thus you have not told us anything we can use to diagnose the problem without being there.

 

[shadowstar57]

Appreciate the responses. I'm a newb, so apologies if missing info. It is city water, no hot water recirc (that I know of).

Since we moved here last year, hot water pressure was always terrible, and some days down to a trickle (cold water fine). One day (didn't recognize connection at the time) I had turned off the sprinklers for the winter, and some time later, the hot water just 'popped' one day flowing strong, and stayed running great. Until this week when I started sprinklers back on again.

This past Sunday night I ran the sprinklers for the first time, on Monday morning no hot water. I opened up all the hot water faucets in the house, and after a few minutes, 'pop', hot water flowing again. Same thing next day, sprinklers ran overnight, and in the morning, no hot water. Turned on all HW outlets, and hour later, 'pop', hot water out.

If its a valve sticking somewhere, where would those valves be located, how can I check? I'll pick up pressure gauge this weekend to test drain valve. I do remember months back I tried cleaning out the HW tank, and only trickle came out of drain. After a while, it finally started flowing out. Some sediment, not a ton, but now in retrospect, seems it might have 'popped' the air just like now. Water temp is very hot, even at lowest setting, so heater is working fine.

Seems to me the sprinkler system is introducing air somehow. Maybe it's closing too fast or too slow... Too much/little pressure...

anybody seen anything like this before?

 

[Reach4]

If its a valve sticking somewhere, where would those valves be located, how can I check? I'll pick up pressure gauge this weekend to test drain valve.

I am thinking it would be on or near the top of the WH, but let's get that pressure gauge result. There are also things called heat traps, and maybe one of those could be a problem. I don't know. I am not a plumber.

Presuming the water pipes all come in and out of the top of the WH, you might post a photo of the top of the WH and the pipes within a foot of the top of the WH.

I do remember months back I tried cleaning out the HW tank, and only trickle came out of drain. After a while, it finally started flowing out. Some sediment, not a ton,

Weird. That pressure gauge result will be interesting.

Another thing that could be useful would be the date code. I would not replace a WH just because the WH is 20 years old, but you have a symptom.

What kind of pipes do you have? Galvanized steel, white PVC, tan CPVC, copper, or what?

What hardness is your water? The town's website might have that info, or a phone call to the water department may give you that number? While you are at it, what is the pH if they have that info for you? These last two things are not directly related to your symptom, but while you are thinking about your water system, those might be useful to plan possible improvements.

 

[shadowstar57]

Thanks, attached picture, as you see, just a straight install. No softeners, filters, or anything else of the kind on premises. The water here is pretty hard (Tampa, FL), so sediment may be a concern, but why is the irrigation system the catalyst? And why does it just 'pop' back to normal. No loud sound, no sediment comes out, and the tank does not suddenly start filling up when it does either, it just flows normally again.

All white PVC around the house, and looks like CPVC coming in/out of hw heater.

House is only about 10 y/o, water heater the same, but even at it lowest setting, it heats up extremely hot, so it's working great. We've had low hot water pressure issues on and off since we moved in last year, but after sprinklers turned off for winter, problem resolved. Now, sprinklers back on, problem back.

 

[Reach4]

I don't see the stuff atop your water heater that I was speculating about.

http://www.tampagov.net/water/how-do-i#hardness says " 8 to 17 grains per gallon". A softener for your indoor water would be a nice upgrade.

but why is the irrigation system the catalyst? And why does it just 'pop' back to normal.

Don't know. Interesting question. After you locate the blockage, we can speculate on that.

 

[WJcandee]

Where does the cold water input to your hot water heater branch off of the main? What if any valves are there? Is there an expansion tank somewhere? How is it connected, and to what, and where?

Is there a backflow valve associated with your sprinkler system? Where is it connected to the main (i.e. at (or in) the meter or at the branch of your sprinkler system, or somewhere else)? Where does the cold water to the sprinkler system connect to the main?

Maybe a simple straight-line drawing showing the branches of your system and the connections and valves at each place will give us a clue.

HJ has said that it isn't air. So it isn't air. (Where is this air coming from, anyway?)

It sounds much more like a sticking component: backflow preventer, pressure reduction valve, check valve, mixing valve, maybe even expansion tank or shutoff valve doing something unexpected (or expected given its function and a defective system design). I would guess that there is limited pressure going INTO your water heater, or something stopping what's coming out. But a diagram would help.

As to the stumped plumbers, understand that there are guys who have a basic knowledge of what they are doing, and limited interest in learning or doing more, and then there are folks like Terry, HJ, Cacher Chick and others that are at the top of the plumbing game, and thoroughly-understand potable water system design and the operation and interplay of the components of such systems, expected and unexpected. You have no idea which kind of plumber was out at your house. My guess is that it wasn't the latter kind.

 

[shadowstar57]

Thanks for the response! From what I can see, the water main breaks off into the house and irrigation right outside house (see picture below). I say that because of the water line right behind the sprinkler T on the picture.

Other than that, I can see no other valve anywhere else. Just the main shutoff one pictured, and the ones each on the in & out of the hot water heater as pictured earlier. No expansion tanks or other control valves of any kind. From the sprinkler pic, that is the 'pressure vacuum breaker' serving as backflow preventer.

Should I dig up where the sprinkler and water line from main connect? Would there be any valve connected there, and if so, would it cause a issue like this? Where else can I look?
Thanks!!

 

[Smooky]

Have they checked the heat traps on the hot water heater? I would start there.

 

[shadowstar57]

They didn't open any of plumbing lines to check inside, how would those present this kind of problem? Sediment jamming up something? If so, then wouldn't sediment come out the faucets when it 'pops'? thanks!

 

[Asktom]

I agree with Smooky.

 

[Smooky]

There could be a little calcium build up or trash that holds the ball until... Running the sprinkler may cause a slight drop in pressure in the cold water line. The hot water is at a slightly higher pressure at that point, pushing back on the trap and it presses against the ball or what ever and presses it past the calcium again and holding it until it is forced back out. It could happen like that, maybe. So that is why I would do that first to eliminate that possibility.

 

[Reach4]

A sticking ball could explain the symptoms. A pressure gauge reading at the WH drain during the problem could eliminate one heat trap as the cause of the problem.

 

[shadowstar57]

Excellent, would this be something a novice like me could try to troubleshoot? If so, how to go about it?

Or is there a way to flush out/clear out the debris without opening the pipes?

thanks!

 

[Smooky]

I would just take them out if they are there and see if that solves the problem. Do you have other back flow preventers? You got to start somewhere.

 

[shadowstar57]

Thanks!! Is this the heat trap? So I'd cut the pipe right here above the junction and remove the trap with a wrench? Is the buildup around it right now a sign that it is the problem?

 

[Asktom]

Alas, back to square one - there are no heat trap nipples on the top of your heater, just CPVC male transition pieces.

 

[shadowstar57]

Doh! Would installing those heat traps work?
Could it be that the irrigation system is causing some sort of suction/pressure issue out of the cold water inlet of the water heater tank and that's preventing hot water to come out of tank later?

If not, what next to check?

 

[Reach4]

Doh! Would installing those heat traps work?

Work to help solve your symptom? NO.

If not, what next to check?

Pressure at the WH drain during the symptom.