Toilet ballcock dripping for a long while after flushing

[Gwynston]

Recently the toilet fill spout drips for a long while after flushing. It's not leaking - I can push the ball down and when it's filled another few mm the drip stops. So on it's own it's just not shutting off sharply - and it takes hours of dripping through the night to fill that last bit to close the valve.

Is there any adjustment or cleaning I can do to fix it, if it's just due to it being a bit old and sticky?
I've seen this other similar thread , but changing the washer didn't seem to help:

toilet drips after being flushed for a while

i have dismantled it all, cleaned the valve up havent replaced the washer (but it looked ok) was a bit mucky in there, but doesnt seem to have improved it (didnt replace the washer as at the time wasnt aware what sort it was and havent got one yet it stops if you hold the ball up for a...

www.diynot.com

 

[oldbuffer]

Two alternatives:
1. Change the diaphragm washer in the inlet valve. These go hard with age and require increased pressure to shut off. Post a photograph of the valve and someone may be able to tell you what type it is.
2. Change the whole inlet valve for something like a Fluidmaster with brass shank.
3. Either alternative will require the water to the WC cistern to be turned off.
4. Alternative 1 can be done without emptying the cistern. Provided its a fairly common diaphragm washer, its generally a cheap and easy fix.

 

[Gwynston]

 

[Gwynston]

Thanks for the advice!

This is the washer - around 33mm.
I gave it a good clean - lots of black rubber residue came off and some gritty bits. That seems to have helped with the drip. If it comes back, at least I can look for a replacement. Are they easy to source?

 

[opps]

Less than a quid from your local plumber's merchant. It is a 25p component.

I am not a plumber but I vaguely remembering someone saying that smearing a little bit of silicone grease (read: not Vaseline) will stop the rubber from sticking to the housing/fittings. Hopefully a proper plumber can confirm/deny that.

 

[oldbuffer]

Looks like a Delchem diaphragm washer. Toolstation stock them, Screwfix appear not to. B&Q have

Plumbsure Rubber Ball valve Washer, (D) 30mm Pack of 2.​