Water hammer.

[SMB]

Hi,
We get water hammer from the toilet when the water inlet valve closes. The valve is low pressure feed from the tank in the attic.
Though this is not much and normally would not disturb anyone, old age requires that I have to get up in the middle of the night.
Anyway, as all pipes are below the floor and not accessible, do I fit an arrester before the service valve or after the service valve for the toilet?
Thanks.
SMB

 

[Best]

Hi, are you sure it is tank fed?
What sort of fill valve is it? An ordinary ball valve type can cause noise & hammer. Check & replace the diaphragm washer on these.
I would think of replacing the fill valve with the red topped Fluidmaster Pro (brass tailed) fill valve or similar.

 

[SMB]

Yes, tank feed. I live in a bungalow, so the tank is only 4/5 ft above the ceiling.
Not the conventional ball valve,

 

[Best]

Some of these modern fill valves do still make a thump noise as they cut off, but usually it's on mains supply. Water hammer I find is mainly from the part 1 ball valve on the cold water tank as it starts to shut off.
I would still consider replacing WC fill valve with a different make.
If you do fit a shock arrester, put it above the isolating valve if possible.

 

[SMB]

Will try the arrester first, as it is easier to fit. Then the valve you recommended.
Many thanks for your VERY prompt help.

 

[Best]

Will try the arrester first, as it is easier to fit. Then the valve you recommended.
Many thanks for your VERY prompt help.

It's a strange one, but all you can do is try that.
I am stating the obvious, - but are you sure the noise originates from the toilet fill valve and not the cold water tank ball valve after you have flushed the loo?