New Fluidmaster float valve installed problems with flush

[jodee]

Hi,
Plumber installed new fluidmaster float valve in toilet last week. flushes okbut every now and then it seems to do a mini flush which lasts about 6 seconds - i can hear the water 'hammering' in the pipes when it stops.
Plumber came back, said nothing wrong with float valve, he thought he had increased water pressure too much which has now been adjusted.
the other problem with this mini flush is that it happens at random so when I am having a shower I now get a blast of scalding water.
plumber wont' seem to hang around to wait to hear the problem.
any ideas please.

 

[gas4you]

Strangely enough I fitted one of these to my toiler Thursday.

Sounds as though he has set the valve to fill the cistern too high, so it is sometimes sticking and overflowing.

It is this 'mini flush' that is the overflowing.

Set the fluid master one notch down and see how you get on.

 

[JohnD]

if you post a pic of the inside of the cistern it might spark some ideas

is the cistern fed at mains pressure or from a cold tank?

 

[jodee]

thanks guys for replying - i still have instructions but don't want to attempt adjusting valve myself (DH won't touch it either!), so guess plumber will have to make another visit.

sorry, can't do pics at the moment, but it is mains pressure.

 

[gas4you]

It is either a simple case of sliding up the grey plastic clip on the main shaft and gently pushing down on the top of the valve, or it may even be simpler than that and just need the black adjusting 'knob' turning to lower the float position in the cistern slightly. This can be done with finger strength or a cross head screwdriver.

you do not have to touch any water connections or joints to carry out either of the above.

 

[TicklyT]

If your WC has a flush valve rather than a syphon, check it is seating properly.
A bit of grit lodged on the valve seat could allow water to slowly trickle from the cistern into the pan. Eventually the float valve will open to make up the level in the cistern.