Spiral spun steel galvanized iron water supplhy pipes in an older building - a possible location for pipe vibration or of whistling or shrieking water pipe noise © Daniel Friedman Building water supply pipe whistling or shrieking noise causes & cures
     

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Building water supply pipe noise diagnosis & cure: whistling, shrieking water pipe noises can drive you mad. Here we discuss the causes of water supply piping noises such as whistles or shrieks, we cite pipe noise research, and we explain how these whistling pipe noises can be cured or prevented in the first place.

Other types of building pipe noises both in the supply system (such as water hammer or pipe vibration) and in the plumbing drain system (such as gurgling drains) are discussed in companion articles linked to at More Reading at the end of this article.

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Water Pipe Whistle or Shriek Diagnosis

Foam insulation in plumbing pipe chase (C) D Friedman Eric GalowReader question:

Since this past fall, I started to get a whistle in the pipes. I Have tried to look it up and get never the same answer. I just saw that could have been turning the outside faucets off could have caused backed up the air in pipes.

I am not sure what to do, as I am selling my house and I don't want someone to turn them on and hear that and be turned off.

A couple people have said [that I should] turn all the water faucets on at once for 5 minutes, as that would work.

I just want a professional, easy solution, because I can't hear [the pipe whistling sound] when the outside hose front or back of the town house are on. Nor do I hear the pipes shrieking when the bath room basin, bathtub, clothes washer are in use, nor when you flush toilets.

[The sound is heard at] the kitchen sink. The pipe whistle sound is not so bad there but then when we go to the second floor of the townhouse, that's when the tub and sink in there [make a whistling sound when in use]. [The water pipe whistling noise becomes much louder ] when the shower is on

Reply: here's where we start diagnosing whistling pipes

Water supply piping noise complaints are usually related to the pressure and flow velocity of water in the piping system. Because water pipe noises tend to be greater at higher pressures or velocities, often we can immediately stop the noise by adjusting water pressure OR water flow rate.

At PLUMBING NOISE CHECKLIST we note that plumbing noises that produce high-pitched hissing or whistling sound may be heard as water runs through building supply piping. This sound should stop immediately when you turn off any fixture that is running water in the building.

You may be able to stop or reduce plumbing supply piping noise by changing the water system pressure at a municipal water supply valve. Try first just slightly reducing the incoming water pressure by closing the main water shutoff valve about 1/2 turn while you hear that piercing pipe whistle (you'll have to take one hand off of at least one of your ears to take this measure).

Now we'll get more specific about how we diagnose and fix this horrible water pipe sound

History as a clue in diagnosing building water pipe noises

Main water shutoff with a lead entry main (C) Daniel FriedmanIf you think that this problem was not present when the building was new but has been getting worse over time, that argues for a mineral deposit or debris deposit, possibly along the length of piping but also possibly in a faucet, control, even a fixture spout strainer that is having effect.

Mineral deposits, if that is a factor in pipe noise (see corrugated piping noise research cited below), won't disappear by simple flushing.

If you think that the problem has always been present then I suspect a pipe layout, design, support, or one or more individual valves, controls, or even a pressure tank problem.

Watch out: while you're inspecting the plumbing system be alert for lead supply piping (red arrow in our photo) that may be at end of life or might be a health concern, and look for leaks, inadequate pipe support, or other stuff you failed to notice that you might fix before a plumbing leak becomes a catastrophe.

Running faucets to "fix" a pipe whistle noise by flushing the water system

I'm doubtful that just running all the faucets for an interval will fix a pipe noise, except on the slight chance of flushing out a bit of debris somewhere that happens to block flow so as to cause the flow rate to set up a harmonic vibration or cavitation in the piping system.

Flushing air in water supply piping to remove a pipe whistle or shriek

I'm also a little doubtful that air in pipes would cause an ongoing whistling noise. It is possible to trap a bit of air inside of a horizontal water (or hot water heating system) pipe, and I agree that at least in theory the effective reduced diameter of piping in the area of air trap might be related to pipe noises.

But because unlike heating systems, water flows in building piping generally at higher pressures and flow rates than in hydronic heat (where air traps are more common), I'd expect air to be forced through the piping and discharged at faucets even if there was a recurrent source of air in the system (such as a well piping or control or air volume control defect ).

Details about these points are at

List of Common Sources of Pipe Whistle or Shriek Sounds

I have found a range of plumbing noises, banging, clanking, and whistling that occur when water is run in some buildings and that would diminish or stop entirely when we changed the flow rate to faster or slower than a critical rate that seems to set up a vibration in the system.

Sometimes even a small flow rate such as a filling toilet can cause a horrible shrieking or whistling in the supply pipe system, so I infer that the sound is not simply caused by a high flow rate.

Squeals and shrieks from water pressure tank

A squealing water pressure tank sound is often due to water passing through a restricted valve or pipe clog.

Shrieking from a water pressure tank that incorporates a bladder may be due to a partly collapsed bladder or obstruction at the tank entrance fittings.

Details about this point are at WATER TANK BLADDERS & CAPTIVE AIR

Other Sources of Building Shrieks & Whistles probably not related to water piping

Before beating whistling or shrieking pipes into a quiet state we should be quite confident that the building noise complaint is only related to water supply piping, that is, the whistling or shrieking sound is not related to or caused by the drain system, and more suitably, not related to hot water heating equipment nor hydronic or steam heating system noise.

Details are at

Cavitation in water piping: holes, leaks, valve design as noise sources

A high pitched shriek or whine also occurs during fill-ups of water tanks whose water level is controlled by a float. In that case the noise seems to come from a combination of stick float mechanism that may not fully open the fill valve and thus a partial restriction in the water line.

Some discussion of the effects of holes in piping systems and the causes of cavitation inside the piping system is in order. I suspect, based on limited field testing and a review of research literature that cavitation may explain some water pipe whistling and shrieking. You can demonstrate the hypothesis that cavitation occurs in some water control valves at some valve positions by opening or closing the valve just slightly from its current position.

For example at our offices in Mexico water is supplied by intermittent, varying pressures in the street water mains from which water is pushed by city pressure to a rooftop water storage tank. Water to the building is then fed downwards from that tank - a common system world wide.
See ROOFTOP WATER TANKS

I have observed that at times when our rooftop water tank is filling the whole water system produces a horrible shrieking sound that some visitors describe as water pipe whistling. I speculate that the noise is due to cavitation in one of two locations: the inlet water main valve or the float valve that controls filling of the water storage tank.

I find that while the pipe whistle-shriek is active, if I zoom over to the main water shutoff-valve and close it slightly, the shrieking stops immediately. If I re-open it to its prior position the whistle renews until the water tank has filled.

This sound does not always occur, depending probably principally on the supplying water main pressure but possibly on other variables in temperature, even barometric pressure, or the condition of the water tank float valve.
I don't claim this is the only possible explanation of water pipe whistles but it seems a likely one.

We also observed both whistling and banging clanging water hammer in the water supply piping system of the Casa Azul hotel in Queretaro, Mexico - an incredibly loud sound that would appear or disappear depending on how many fixtures were in use and probably on variations in the hotel's water supply pressure.

Water supply pipe shriek or whistle noise diagnostic questions

But I agree I've not researched enough on whistling sounds in plumbing systems. Can you tell me more precisely (you already took a stab at this)

Cures for Water Pipe Whistling & Shrieking

Besides these research citations on water pipe noises, people have invented things intended to silence the pipe whistle. Not surprising, some of the inventors also appear among some of the pipe sound research.

Below we include a list of pipe noise reduction measures, starting with a few installation details. But the key steps in managing pipe whistling and vibration caused by water flowing through the piping system involve adjusting the pressure and flow rate in the system.

JGL Acoustics recommends that the maximum water flow rate in gallons per minute in a building piping system ought to be 4 feet per second. Translating this into something a normal human being can understand, that means that water flow in supply pipes should be:

Water Pipe Flow Rates in GPM to Avoid Pipe Whistling or Shrieking Noises

Water Pipe Diameter Maximum flow rate
1/2" 2.5 gpm
3/4" 5.5 gpm
1" 10 gpm

Notes:

Separately, Canadian CMHC research (1996) found that increasing water pressure increased the noise level in buildings by +5 dBA to +9dBA when water pressure increased from 40 psi to 100 psi (which is high and well above recommended in-building water supply pipe pressures).

Interestingly the CMHC research found that the noise transmission varied by building structure (wood vs steel frame, for example) but CMHC found that there was not a significant advantage in sound reduction obtained by increasing the pipe diameter from 1/2" to 2".

Table data adapted from "Plumbing Noise", JGL Acoustics, publication No. 8, JGL Acoustics, Inc., 6421 Lake Washington Blvd. N.E. # 209, Kirkland WA 98033, Tel: 206-827-1057

Noise isolating pipe hanger, plastic (C) InspectApedia

Water supply pipe noise research: cavitation, flow, whistles, shrieks & Building Plumbing System Noise Reduction Methods

Here are some interesting citations on the topic. They indicate that you and I are not totally weird in looking for a solution to water pipe sounds.

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Continue reading at WATER HAMMER NOISE DIAGNOSE & CURE or select a topic from the More Reading links or topic ARTICLE INDEX shown below.

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WATER SUPPLY PIPE WHISTLE NOISE at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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