Buzzing, humming main water connection

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Keith Bellairs

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Our town has a lift pump 15' above our place. It is taking water from wells up to a reservoir. The water to our house comes from the pump house. When the pump is running there is a consistent 60 cycle hum that enters our house through our water service. It is extremely difficult for my wife at night - kind of like living with a low buzzer going constantly.

We can stop the noise entirely by shutting off the main shutoff in the house. The town paid our plumber to install a noise isolation segment between the service and the shutoff. The isolator (flexible segment with braided steel around it) may have reduced the volume of the noise that we hear when the valve is open but it certainly has not eliminated it.

Previous owner of our property complained to the town and they tried to figure out how to fix it. No luck for them or for us. Would love suggestions from anyone who has dealt with this kind of nuisance.

BTW, we followed the threads on TerryLove to select and install our Toto toilet. It could not have gone easier. Thanks a million.
 

Jadnashua

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I wonder if a small well-type bladder tank might dampen the vibrations? It would act like a big hammer arrestor.

This is a tough one. If you put a water pressure gauge on the supply somewhere, does the needle vibrate, or is it steady? That would help determine if it is the pipe vibrating from the pump, or if it is vibrating from water pressure pulses, which would each require different fixes.
 

Keith Bellairs

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I wonder if a small well-type bladder tank might dampen the vibrations? It would act like a big hammer arrestor.

This is a tough one. If you put a water pressure gauge on the supply somewhere, does the needle vibrate, or is it steady? That would help determine if it is the pipe vibrating from the pump, or if it is vibrating from water pressure pulses, which would each require different fixes.
Tank is an interesting idea. Our water comes into a small utility room on slab floor. There is already a washer and dryer. We took out tank water heater and put in tankless on wall. Wife says noise was worse after that. Our town is going to water meters so that's yet to be plumbed in.
 

Keith Bellairs

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IF isolating your system from the main by shutting off the water eliminates the sound, maybe installing a pressure regulating valve, even though you do not need it, might do the same thing.
I never heard of a pressure regulating valve before. Looked at the specs. I wonder if they are designed to deal with 60 c/s pressure changes. The simple ball valve we have now works to completely stop the vibration when it is closed, and completely allow it when open.
 

Jadnashua

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If the sound stops when you shut the valve, it sounds more like it is pressure waves than pipe vibrations. A bladder tank would act like a big hammer arrestor, while a dedicated hammer arrestor might work as well. Those are inexpensive and you can get them with a hose type connection you could try at the washing machine. Since the WM is near the entrance, that might work and would be easy to try.
 

Keith Bellairs

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I agree that it seems to be a pressure wave hammer. Never thought of trying a hammer arrestor. Duh. Typical hammer is a more isolated big bang, isn't it? Any thoughts on different kinds of hammer arrestors?
 

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A small pressure tank made for a well would serve as a bigger heavy duty arrestor able to handle bigger water surges. I see there are 2 and 4 gallon versions available pretty cheaply. A thermal expansion tank is also worth considering. You want to have the pipe from the new tee to the pressure tank be large rather than reducing the pipe at the tank.

Each of those would have a schrader valve (tire valve) for the pre-charge air. I would set that precharge amount maybe 5 to 10 PSI lower than your normal water pressure. This is very different than the precharge you would use for a well (2 to 4 PSI lower) or water heater expansion tank ( 0 to maybe 20 PSI higher). Others may have a different opinion on that. Precharge air is always set with 0 PSI on the water side.
 

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Thermal expansion tanks aren't designed for potable water
Not quite true as I understand it...one designed for a heating system, true, it is not designed for potable water, but one for expansion due to thermal on the potable side is designed for it. A bladder tank designed for use with a well pump also is, and has a bladder probably designed for greater expansion/contraction than one designed for use as an expansion tank. But, you should not be expecting huge volume changes, but lots of small variations. Still could wear out faster as a result, though. At least some hammer arrestors use a piston verses a bladder, and that should last as long as the seal.
 

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I tried a simple washing machine hammer arrestor and it does not help. I think they are tuned for a single big bang. A continuous hum needs a different response curve. I have seen hammer arrestors online that have an adjustable air pressure chamber. Sounds more tunable.
 

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My guess is that arrestors have too much "unsprung mass" to work at 60/120 Hz. In other words, even if you could get it centered, the "slug" inside the arrestor may be too heavy to move back and forth fast enough. Worse yet, when we hear 60 Hz, often times it is really 120 Hz -- the frequency of the power dissipation with a 60 Hz AC source.
 

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An expansion tank's bladder may absorb the sound better, but then again, it may just act like a speaker cone. You might try using something like a SS braided hose like is often used for a WH supply. Or, to get really high tech, maybe one of these
http://weicco.com/ExpansionJoints/ThreadedPipe.aspx to break the supply from outside to the house.

The rubber coupling should disconnect the hard pipe.

Have you been able to determine if the noise is being transmitted by the pipe or the water pulsing? Did you hook up a pressure gauge to see if the hand was vibrating? Can you feel any vibration?

These are only guesses...seems like not too many people, at least in residential, have experienced this, so there's not a lot of discussion or evidence on what may work, which means, you'll likely have to experiment. Please do fill us in on what works and what doesn't. ONe of those little tidbits that may help someone else later on.
 

Keith Bellairs

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I did put an audio freq meter on it and it is indeed 60 c/s with a strong 120 harmonic. There is already a braided SS hose section after the main shutoff. We felt like it helped some but not enough. Have not opened it up to put a pressure gauge on it.

Thanks for the ideas. Here's the puzzle. The vibration/hum is clearly caused on the supply side by the town lift station near us. We hear the hum when the town's pump is running. The sound comes into the house and we think we hear it on all the pipes. But if we shut off the main ball valve on the supply, the sound stops. That does not seem to make sense for either vibrating supply pipes or water hammer - wouldn't the hammer bang on the ball valve too? We think the sound may be reduced if we are running water.
 

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Yours is an unusual case for a homeowner. I think this is a problem that should be solved by the water system rather than by you. Yet you have a reality to deal with.

Regarding working around the problem, there is another kind of water hammer arrestor. The old kind, before the piston types came out, was just a capped length of pipe that you hope would have air in it. Over time the air would dissolve in the water, so that would make it not do its job. When you turned off the water and drained the pipes, you hoped the water would drop and you would get air again. It may not work as hoped.

Anyway, I am thinking a bigger version of that might work for you. Maybe have a positive means to drain the pipe. You would make it with bigger pipe. Maybe 3 inch schedule 40 PVC. That way there would be no piston, and the contained air could act as a capacitor would. On the other hand, that 2-port (dual port) diaphragm pressure tank sound encouraging. If it was not perfect to begin with, I would partially close the input valve. That way you have more of an RC circuit equivalent with a higher time constant.

I also wonder if a pressure regulator before the pressure tank would help. Its moving part may be too massive to track the 60 Hz component. If they had built a water tower next door, this problem would not occur. If the pump motor was 3-phase power, I would have expected this to be much reduced... but you would then have a 180 Hz component, at lower amplitude, rather than 60 Hz.

Why does closing the valve stop the hum? I am guessing that the sound radiating area gets reduced.

Getting wild below, so most people should stop reading now.
This next part is not quite in jest, but I think it is probably not practical. Suppose you put a closed end water filled pipe that was a quarter wavelength of 60 Hz in water. That would be about 6.2375 meters long. This would be analogous to a 1/4 wavelength stub in RF work... it would serve as a notch filter of the 60 Hz frequency and its odd harmonics. The speed of sound in water changes with temperature. Pipes change length with temperature. The frequency of electricity can vary in the short term. Maybe there could be some variable length trombone-like device for tuning. They are cheap in small PVC surprisingly.
 
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Jadnashua

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It sounds like it is pulses in water pressure, which a pressure gauge would likely show readily (most of those available aren't damped). A prv doesn't do much unless you have water flowing through it, and may not be able to respond quick enough to pressure pulses at that frequency. Something like that vibration damper fitting I linked to might work. Those are designed to prevent pipe damage between equipment and the supply lines, more from movement of the machine verses vibrations, but still, it provides a flexible coupling between the supply and the house. A capped, dry air tube as an arrestor wouldn't last long...I think the vibrations would expose more water to the air, and the air would be absorbed quicker. Maybe a longer section of reinforced supply tubing...if a piece helped, more may help enough to attenuate the sound enough to be satisfactory.

For about $15, you can buy a gauge, screw it onto a hose bib, the drain on the WH, or a washing machine supply valve...only take seconds, and easily removable without soldering or tools. An auto mechanic's stethoscope might be useful as a rough tool to determine before/after any additions as to their efficiency, but if it's audible without, probably not worth buying one, at least for this task. Easy enough to make with some tubing and a rod the right diameter to fit inside the tubing.
 

Jadnashua

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It sounds like it is pulses in water pressure, which a pressure gauge would likely show readily (most of those available aren't damped). A prv doesn't do much unless you have water flowing through it, and may not be able to respond quick enough to pressure pulses at that frequency. Something like that vibration damper fitting I linked to might work. Those are designed to prevent pipe damage between equipment and the supply lines, more from movement of the machine verses vibrations, but still, it provides a flexible coupling between the supply and the house. A capped, dry air tube as an arrestor wouldn't last long...I think the vibrations would expose more water to the air, and the air would be absorbed quicker. Maybe a longer section of reinforced supply tubing...if a piece helped, more may help enough to attenuate the sound enough to be satisfactory.

For about $15, you can buy a gauge, screw it onto a hose bib, the drain on the WH, or a washing machine supply valve...only take seconds, and easily removable without soldering or tools. An auto mechanic's stethoscope might be useful as a rough tool to determine before/after any additions as to their efficiency, but if it's audible without, probably not worth buying one, at least for this task. Easy enough to make with some tubing and a rod the right diameter to fit inside the tubing.

If shutting the supply valve stops it, a prv might do the same thing...until you use water, essentially, it disconnects the supply from the house once the outlet pressure is reached, and only opens back up when you flow water. You'd have the pipe on the supply side of the prv that could vibrate, but not those after it.
 
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