# Fog horn sound sometimes when water drawn. Please Help!



## Derek Diggler (Feb 10, 2020)

I have a 4.5 year old home with a tankless water heater in my crawl space. The past couple of weeks I have noticed that all of the sudden I am  randomly hearing a fog horn sound from my crawl space. It happens randomly when a sink is turned on, washing machine on, toilet flushed ect. It doesn’t seem to matter whether drawing hot or cold water either. I went under my house and it appears I have some sort of blow off valve that shoots water out when it happens (I have been catching the water). Please see attached pictures of my set up in my crawl space. Please help! How can I fix this problem?
Thanks, Derek


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## pjones (Feb 10, 2020)

I would bet your expansion tank has a failed bladder. Time to replace it. 

Tap the side of it with something metal. If you hear a hollow ring sound then it should be good still. If you hear a dead thunk then it’s filled with water and needs replacing. 

If it’s time for a new one you can get by for a while by draining that tank and putting it back on empty.


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## Derek Diggler (Feb 10, 2020)

pjones said:


> I would bet your expansion tank has a failed bladder. Time to replace it.
> 
> Tap the side of it with something metal. If you hear a hollow ring sound then it should be good still. If you hear a dead thunk then it’s filled with water and needs replacing.
> 
> If it’s time for a new one you can get by for a while by draining that tank and putting it back on empty.



Hi PJones,
Thanks for responding. I tapped on it with a wrench multiple times and the top half sounds hollow but the bottom half sounds full.. any idea what that means? I’m not really too familiar with its functionality to be honest.


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## bud16415 (Feb 10, 2020)

I’m assuming the black pipe is incoming from your well and the water comes in and compresses the gas in the bladder in the tank and then the pressure switch to the left turns the pump off when it hits some pressure. Where the water and sound is coming from is a pressure relief valve preset to 100PSI the pressure switch should shut the pump off before it reaches 100PSI. There is a gage you can watch and see what pressure the pump is getting up to by having someone run some water and then shut it off while you are down there. If it is happening when the pressure is lower than 100PSI then the pressure relief valve is bad, if it is getting to 100 PSI then the pressure switch is bad or it is set to high.


If the bladder has failed then you will see the pump running on and off every few seconds. It doesn’t sound like that is the problem to me and your tap test is showing what it should be water on bottom air on top.


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## pjones (Feb 10, 2020)

Hollow on top and full on bottom is normal and indicates a good tank. 

Follow the advice above and let us know what you find. Could be a lot of different possibilities at this point. Let us know what pressure it happens at and what pressure is stamped on the relief valve.


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## bud16415 (Feb 10, 2020)

pjones said:


> Hollow on top and full on bottom is normal and indicates a good tank.
> 
> Follow the advice above and let us know what you find. Could be a lot of different possibilities at this point. Let us know what pressure it happens at and what pressure is stamped on the relief valve.



The photo shows it at 100PSI the system should never see that high IMO makes taking a shower no fun..


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## bud16415 (Feb 10, 2020)

As a side note if you hold on to the black pipe coming from the well you should be able to feel when the pump kicks on and off. I’m assuming your pump is a submersible and in the bottom of the well.


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## Jeff Handy (Feb 10, 2020)

Looks like the gauge is showing approx 57 psi in both pics showing the gauge. 

Which is normal for a 40-60 pressure switch for a well. 

Foghorn sound is usually vibration of some sort. 
Loose or worn washer inside a valve, or a valve almost partially closed can cause that screeching humming noise. 

Yes the pressure relief valve could be going bad, and vibrating like a harmonica as water is exiting through an almost closed valve. 

Could also be clogged or dirty filters in the water heater causing back pressure.


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## bud16415 (Feb 11, 2020)

Jeff Handy said:


> Looks like the gauge is showing approx 57 psi in both pics showing the gauge.
> 
> Which is normal for a 40-60 pressure switch for a well.
> 
> ...




57 PSI was it going up or coming down when he took the picture?


I don’t think I have ever changed the filter on my water heater. That can cause back pressure?


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## pjones (Feb 11, 2020)

bud16415 said:


> The photo shows it at 100PSI the system should never see that high IMO makes taking a shower no fun..



I see that now. Thanks. Looks all shiny and new. It would surprise me if it had become weak so quickly but I’ve seen new ones fail before the in a similar manor.


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## Jeff Handy (Feb 11, 2020)

The tankless heaters can have frequent filter issues.

And I was looking at the pressure gauge, not the setting on the relief valve, so my bad if we were on different wavelengths there.


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## bud16415 (Feb 11, 2020)

A clogged filter down stream is about the same as a valve being shut or turning the water off at the kitchen sink. it will stop the flow but shouldn't change the pressure behind it.


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## Jeff Handy (Feb 11, 2020)

Yes, instead of back pressure I should have said flow restriction.


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## Derek Diggler (Feb 16, 2020)

Thanks everyone for the responses. Sorry it’s taken me awhile to get back under the house with enough time to have someone upstairs try and get the fog horn sound to happen again. I was able to do that tonight after sitting under for 20 mins. After running water from sinks flushing toilets it took running the washer to get it to happen this time (most of the other times it happens when running the sink/flushing a toilet ALL randomly).
From what I could observe, watching it happen in front of me, the pressure gauge went from hovering under 60 to shooting slightly past 70 and that’s when the fog horn sound happened and water shot out of that pressure valve (I attached some pictures). The black pipe is my well line. I’m not sure what action the washing machine was in for it to make the gauge want to jump to 70 but that’s def when water blew out of the pressure release valve ? Does this make sense to anyone?  Thanks!


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## Jeff Handy (Feb 16, 2020)

So far, it looks like bud’s post # 4 is coming true, in both ways. 

High tank pressure rising beyond 60 psi, pump pressure switch might be randomly sticking on sometimes. 

And pressure relief valve letting go too soon, above 60, not waiting til 100 psi.


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## Jeff Handy (Feb 16, 2020)

Can pumped water pressure artificially spike, momentarily, when a fast closing valve shuts, like with the washing machine?  

Either way, maybe just replace the pressure relief with another one, for starters?


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## Derek Diggler (Feb 17, 2020)

Thanks Jeff. What is the easiest way to go about changing that pressure relief valve? I’m thinking to close the water valve to the far left which would prevent any water in the house from coming back down. Then turn the breaker off to the well pump. (I don’t have a valve that I can turn off on the well side...) Then open the spigot up slowly that is in front of the pressure switch, draining enough water out so that I can change the part. Does this sound about the right way to go about this?


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## bud16415 (Feb 17, 2020)

That’s correct. Then just unscrew the old one from the manifold and put some Teflon tape on the threads of the new one and screw it in.


Wind the tape around the new one in the direction it wont bunch up when it is threaded in. about 4 or 5 wraps will do it.


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## bud16415 (Feb 17, 2020)

Jeff Handy said:


> Can pumped water pressure artificially spike, momentarily, when a fast closing valve shuts, like with the washing machine?
> 
> Either way, maybe just replace the pressure relief with another one, for starters?




What you are describing is what I call water hammer. There is some inertia/momentum to a fast moving column of water being suddenly stopped, but in this case maybe that’s the bump from 60 to 70 PSI. That valve still should not be dumping until it sees 100PSI. It is only there like a fuse to prevent a runaway pump from burning up. I guess the idea is you will see or hear as the OP did the water and that should tip you off to make repairs.


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## Jeff Handy (Feb 17, 2020)

Relief valve says made in China, so might be a piece of junk. 
But everything seems to be made there, nowadays.


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## Derek Diggler (Feb 29, 2020)

Installed the new pressure relief valve over a week ago and since then no more fog horn sound  
Thanks again for all of the input!


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## bud16415 (Feb 29, 2020)

Derek Diggler said:


> Installed the new pressure relief valve over a week ago and since then no more fog horn sound
> Thanks again for all of the input!



Glad we could help.


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