Leaking fluidmaster valve

[Tim]

Hi, I've done a search through the archives, and haven't found anything, so please forgive me if this has been asked before.

I have: toilet cistern; side-mount fluidmaster valve; cistern fills from loft tank; I've removed the pressure reducer from the valve; I've fitter the low pressure washer; I'm in a hard water area.

the problem is this: the valve worked fine initially - silent and quick to refill. However, after a few months, water started coming out of the blue air vent at the top (which I think is there to allow air to be sucked in when there is any sort of back-pressure). I replaced the washer to no avail. I've tried cleaning the plastic housing with a toothbrush (there is some light brown discolouration behind the washer) - also to no avail. I've now resorted to installing the pressure reducer thingy. This has reduced the flow from the top, but not stopped it. And of course now the tank takes twice as long to refill.

Any ideas please?

I was sure it was something to do with the hard water (since it took a few months to manifest itself), but now I don't know.

Cheers, Tim

[Tim]

OK, since I had no response I emailed CMI international (the UK distributor - got their address off the fluidmaster web site). They very kindly offered to send a replacement valve. When it arrives I'll do a little experimentation to see if I can isolate where the problem lies. The water not so much leaks out of the blue cap, more spurts (so much that none seems to come out of the main fill tube and it sometimes drips down the side of the cistern if it sprays at the wrong angle). I'll post results. Cheers, Tim

[Tim]

Well the replacement fluidmaster 747uk turned up. I replaced the twist-off cap assembly (the bit that holds the washer) with that off the new one - no difference.

I replaced the main body of the valve with the new one, and fitted the twist-off cap assembly from the old valve - success! A quiet non-leaky fill again.

I'm not sure quite what this indicates. The body of both valves looks identical. Maybe a bit of debris got wedged somewhere in the old one, though I've tried to have a thorough look and can't see anything.

Hey ho - at least my bathroom floor is dry now!

Cheers, Tim