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Question DetailsAsked on 7/21/2016

We have been experiencing an intermitent fog horn type of sound from our plumbing. Not constant or consistent.

The horn sound is sometimes horrifically loud and sometimes hardly noticeable. If someone is showering on the top floor I can turn on the tap in the kitchen and the sound will go away. Seems to be mostly hot water related but sometimes I hear it when I'm running cold in the kitchen sink. Can go away for months at a time.

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Here is a prior similar question with answer which might help - I must have been tired or lazy that day, because I left out a couple of the common causes, which I add below:

The reason it goes away when you turn on another tap is you are decreasing the pressure in the pipes and also the flow rate in the shower by dividing the flow.

The first key thing to do is determine fi only happening at one valve/usage point, or several. If only happening at one valve/demand point, then probably rebuilding (changing out the seals and washers to stop internal leakage or chattering) or if real worn replacing that valve will solve the problem. Should be pretty obvious if coming from a particular valve - only happens when that one is on AND will be real loud when uyou put your ear to it - will commonly also be able to feel the vibration if you put your hand on it.

Other causes I did not necessarily list in link above (without rereading it in detail):

0) Shower heads commonly do this, also VERY commonly a slightly leaking tub spout diverter valve, especially the kind you lift the knob up on the wall or on the spout to divert to flow to the shower head, but turn-valve faucet type can do it too. In that case, running the water and reopening the valve (so the tub spout flows) then sharply (but not so hard as to break it or the spout off) jerking it up can (unless the seat is badly eroded) stop the minor bypass flow that was causing the howling. Ditto to shower head valves at the shower head - turning off and back on under pressure can stop it at times.

1) unusually high water pressure which results in higher flow rates, hence restrictions (mineral buildup, valves, etc) can cause cavitation (turbulence causing air bubble formation in the pipes) resulting in the sound. Could get a $5-10 hose-thread pressure gauge (designed for use with water systems, typically reading from zero to about 100-120 psi even though your system hopefully is not above 60-70 psi) and check the pressure when the problem is occurring and also when definitely not to see if you are getting unusually high pressure at times when it is occurring. Generally, about 60-70 psi is the most your household system should carry. It may also be that your water supplier (if on public supply) is cranking the pressure up in the system a bit with booster pumps to maintain pressure during peak lawn watering dry periods and you are near a booster pump so the pressure your pipes see goes up at times. Can also very commonly happen the other way - normally high pressure in lines you connect to, but during peak usage periods (morning and evening cooking, washing, bathing times) and peak watering / car washing times the pressure drops off - but in that case you would expect it to happen daily and typically most commonly at night.

2) Could be intermittent if on a water system with variable pressure - like fed from a hilltop pressure tank that might be full or near empty at different times, from a well which might have its pressure tank fill with water at times so does not trap the air in the system, well water getting low (maybe seasonally so months between occurrences) so pump is pulling air into the water which then whistles in the pipes, or a deep well with highly variable water level so the pump is having to lift the water a height that varies many tens of feet voer the seasons, causing significant pressure differences if the pump pressure regulator is not working right. Testing pressure with a gauge at the pump (on the outflow side) would check that.

3) Can also be from a pressure regulator or backflow preventer (usually just downflow from the main household shutoff valve but commonly at pump in a well system) which is sticking a bit closed so when the water passes through it the flow is throttled and causes cavitation.

4) You can try all the different faucets in the house to see which cause it (commonly only the high-flow ones like washing machine, tub (not shower), toilet, maybe outside hose bibs. You might tie it down to one branch of the piping in the house - or might find ALL cause it, meaning is in the piping leading into the house before it splits off to different demand points. Ditto to hot and cold faucets/demands, could narrow it down to one or the other system (though sounds like happens in both with yours) - if same with both then most likely in common cold piping as above, before the water heater lead split-off.

5) I said most likely because a toilet tempering valve allowing backflow through the vavle can also cause this.

6) Kinked feed tubing to a faucet, or kinked flex tubing at hot water heater.

7) Rarely, long pipe runs (common in ranch and exposed basement/crawlspace piping) which are not adequately restrained can set up a resonance or vibration which can be like a howl, a chatter, a whine, or a musical note - just putting your hand on the exposed pipe will stop it or at least dramatically change its tone, and clamping it down with pipe hangers will stop it.

A plumber might track it down a bit quicker than you, maybe not - at $75-150 minimum visit charge plus about that much again per hour - so no real reason to not find the source point yourself. Holding your ear to the piping or using a stethoscope (real one for about $10-15 at pharmacy department or using a tube as one) can make it easier - ditto to at walls and such.

The intermittent part leads me to think it is related to high incoming pressure or incoming air in the line, because a leaky or chattering valve, kinked line, blockage in the line, etc would be expected to do it all the time. Pressure you can check with pressure gage at low point drain (except on boiler - that is low pressure water) or a hose bib which is "downflow" from any pressure regulator. Air you can check for by running a hose into a bucket so the end is submerged and look for significant air bubbles in the water. Put the hose in coiled flat at the bottom edge aimed around the perimeter so the water enters smoothly in a circular direction in the bucket so just the water coming in does not cause bubbles. There may be a few bubbles just from the hose end, but should be obvious if a lot of air is coming out. Also, if a lot of air in the lines, when you first turn on the water or washer first starts flowing you should hear a burst of air or slugs of gurgling sound.

Good luck - please respond back using the Answer This Question yellow link right below your question - always good to hear what the actual cause was to be able to improve future answers.

Oh - one other cause I did not mention that a neighbor had happen once and was driving him CRAZY - a true howling sound almost always at night, and only when the boiler was pumping hot steam through a radiator system - they unfortunately spent a lot of $ trying to track it down wioth probably a half dozen plumbers. Turned out to be the pet dog (which was bedded down in the cellar) being sensitive to a high-pitched whine in a zone valve that set the dog to howling - a plumber finally heard it when he was down there checking for sounds in the heating system.

Answered 2 years ago by LCD

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