Vibrating part 2 cold water tank valve

[mikeguitar]

Hi all.
Sorry for a repeat of a question posted many times before .
My house is 60 years old. The loft cold water tank sits on a purpose built, by the builders,
Platform. It's been ere since new.
I've changed the float valve several times in the past, they are always have a thick encrusted lime scale covering. I just fit a new valve.
Recently the present valve started oscillating whilst filling. Plastic tank,no strengthening plate.
I checked the water surface, not easy task, and there was the tell tale surface waves.
I could stop the vibration by holding the input 15mm pipe.
I fitted new valve, oh god, same result. Not easy for a 6'4 bloke in my loft.
The pipework is unsupported. I'm going to have to build some framework so I can fit pipe clips.
Temp fix, I've wedged some poly styrene between pipe and tank shelf.
Because this problem only just started I'm wondering if thetank support frame work may have moved? Hence stressing the tank

 

[polesapart]

Try a Fluidmaster side entry inlet valve.

Unlikely to be the frame, unless visible issues.

 

[Agile]

Doubt it.

For a start you are meant to have the metal reinforcement plate at the ball valve entry point!

Tony

 

[mikeguitar]

Ok thanks. Tony
I was thinking of getting piece of aly, cutting 1/2" hole in it and fixing to tank internally using the float valve.
Was thinking slightly less than width of tank and nearly to full depth

 

[mikeguitar]

Thanks poles,
I nearly bought the fluid master side entry. With brass threads, wasn't certain if the float may jam on tank side after a year of lime build up

 

[mikeguitar]

Nah I'm talking rubbish.
Make that more like 6"square with the hole about an inch down from the top.

 

[Burnerman]

Consider reinforcing the outside of the tank with some 12mm ply, secured with the valve back nut....once the plastic starts to flex, vibration can start.
John

 

[mikeguitar]

Thanks John.. I'd not thought about ply.

 

[Burnerman]

Anything that makes the tank walls stiffer can only be a good thing......as the valve closes, the tank wall flexes.
Just make sure you reinforce the outside of the tank.....it really doesn't matter what material you use, as it remains dry.
John

 

[oph]

Try a Fluidmaster side entry inlet valve.

Unlikely to be the frame, unless visible issues.

On a toilet cistern yes but not on a cold water cistern........

OP, you've identified the problem yourself. You need more support on the mains water pipe. You could even fit a bigger ball on the existing ballcock

 

[mikeguitar]

Thanks once again oph.
I ll check what's available. I've recently changed all taps in bathroom and installed new shower.
My wife wanted all chrome. Real pig getting access to the hot water tap on bath. Had to make spanner.
Can't see why I could have introduced the problem? No pipework change, other than fitting isolator valves in pipes