A real life problem with plumbing at my house

[iVenky]

I have a problem with plumbing in the bathroom at my condo (quite old) that I am living. The plumbing inside the walls of my bathroom make this whistle noise always and it goes away when I flush the toilet. And then it comes back again after sometime. Do you know what could be happening here?

 

[Andrew Mason]

The problem may be with your toilet. It sounds like a faulty fill mechanism. The sound starts when the toilet tank is nearing shutoff and the fill valve is not closing fully.

AM

 

[jrmichler]

It's a normal problem with toilets. The nearest hardware store will have a replacement valve for about $10.00 or $15.00 or so. Or you can call a plumber if you do not have a friend who can help.

It's wasting water until it's fixed.

 

[iVenky]

You are right. It's coming from the toilet. What's causing the noise? Is it from air molecules in water being forced to low pressure air outside?

 

[hutchphd]

It is likely from the water turbulently flowing through the slightly open (leaky) fill valve. This in turn makes the 25 cm long fill pipe resonate and the sound is carried through the pipes efficiently.
I could have sworn the sound was from the bathroom sink a few months ago when I had similar noise...but there was no leak!.. I turned off the toilet and there it went. It doesn't help that my hearing probably rolls off at 6 kHz at my state of decrepitude.

 

[iVenky]

It is likely from the water turbulently flowing through the slightly open (leaky) fill valve. This in turn makes the 25 cm long fill pipe resonate and the sound is carried through the pipes efficiently.
I could have sworn the sound was from the bathroom sink a few months ago when I had similar noise...but there was no leak!.. I turned off the toilet and there it went. It doesn't help that my hearing probably rolls off at 6 kHz at my state of decrepitude.

Thanks for the reply. So is it caused by the sudden change in the momentum? And where is this energy coming from? Is it just due to the gravitational potential energy of water, as the water is essentially leaking it's similar to having an open value but with a sudden velocity change.

 

[hutchphd]

No I think the water squirting under pressure moves the pipe/valve a little which occludes the flow allowing the pipe to spring back which opens the flow etc...positive feedback and a natural mechanical resonance of a few kHz !. It might even be the same kind of turbulent flow that brought down the Tacoma Narrows bridge (at a slightly lower frequency!)

 

[hutchphd]

As I think about it a better analog is probably an organ pipe...in water the the frequency willbe a factor of three higher because of the speed of sound in water.

 

[iVenky]

No I think the water squirting under pressure moves the pipe/valve a little which occludes the flow allowing the pipe to spring back which opens the flow etc...positive feedback and a natural mechanical resonance of a few kHz !. It might even be the same kind of turbulent flow that brought down the Tacoma Narrows bridge (at a slightly lower frequency!)

Thanks for the reply. That's very interesting. Where does this energy come from that's making this noise?

 

[Delta2]

Thanks for the reply. That's very interesting. Where does this energy come from that's making this noise?

Its from the energy the water has due to its pressure (static pressure) which in turns comes from gravitational potential energy or from some pump that is located somewhere and increases the pressure of the water.

 

[iVenky]

Its from the energy the water has due to its pressure (static pressure) which in turns comes from gravitational potential energy or from some pump that is located somewhere and increases the pressure of the water.

Exactly. That's what I thought

 

[sophiecentaur]

In a lot of houses, there used to be an overflow pipe that sent the trickle of overflowing water outside and down the wall. Very visible. Now they tend to direct overflowing water down the soil pipe and the only clue you get is either that hissing noise or a slight disturbance of the water in the pan.
I had a brilliant fault in my water system once. I was getting hot water (steaming) out of the rainwater down pipe by the back door. Long story short - the heat exchanger inside the hot water tank developed a small leak which allowed hot central heating water into the domestic hot water circuit when the boiler pump was running. That caused the cold water tank level to rise to overflow into the gutter below the eaves.
The plumber came and was gobsmacked when I told him what had to be wrong. He put in a new tank.

 

[etotheipi]

Its from the energy the water has due to its pressure (static pressure)

Thanks for this, it's very interesting! I found a nice commentary about this part specifically here.