Drinking fountain whining sound

[SC_plumber]

I recently changed the water filter in line with the drinking fountain and it now makes a loud whistling/whining sound, at relatively low frequency. The sound will persist as long as the drinking fountain is flowing.

Fountain:

The drinking fountain was part of a Whirlpool WHER25 RO filter, but we are now using a simpler refrigerator filter. The filter is an off brand, but I have used it before with no problems. (IN-WF0130 replaces GE GXRLQR)

History:

There was no sound problem until I replaced the fountain filter two weeks ago.

Since then I replaced the old multi-turn shut off valve with a ¼ turn shut off valve and it was quiet for three days, but now the whining sound is back. It persists as long as the drinking fountain is flowing, but gets much quieter if you turn on the main faucet full blast.

Vibration:

If you feel the pipe around the shut off valve, the vibration is very strong there.

The sound pitch is consistent with a resonance between the fountain valve and the shut off valve, or between the filter and the shut off valve (low frequency sound corresponding to the distances between the filter and valves and the speed of sound)

Plumbing arrangement:

Copper pipe comes vertically through the floor and ends in pipe threads.
Copper pipe threaded end --> shut off valve --> PEX tube.

Pex tube --> quick connect T.

Quick connect T: One line is PEX to main faucet (3/8” id ?)

Second line is PEX to drinking fountain. (smaller diameter)

Shut off valve was multi turn, now is ¼ turn type. Changing this did not solve the problem.

Water pressure:
no gauge, so no way to know what the pressure is. (None of the other
Faucets make any noise, though)

 

[Terry]

You may have a bit of rubber from the old multi-turn stop stuck up in there somewhere.
Maybe. And maybe not.
I would try to back flow the drinking fountain if possible. I don't know how you would do that. I sometimes do that on kitchen sink faucets, but they have two ways in.

 

[Sponsor]

 

[SC_plumber]

You may have a bit of rubber from the old multi-turn stop stuck up in there somewhere.
Maybe. And maybe not.
I would try to back flow the drinking fountain if possible. I don't know how you would do that. I sometimes do that on kitchen sink faucets, but they have two ways in.

Do you mean add a backflow valve ?

Other information: I added 0.5m length of tube between the filter and the fountain and the pitch gets much lower---seems like I need a damper inside the tube.

 

[Flapper]

Do you mean add a backflow valve ?

feed water through it backwards to dislodge debris

 

[IsopureWater]

Debris is most likely the cause.