Plumbing - Toilet Overflow

Soldato
Joined
12 Jan 2006
Posts
4,565
Location
Edinburgh
I'm trying to figure out why our toilet doesn't stop refilling the cistern properly. The toilet flushes fine and starts to refill as it should, the water level then lifts the float correctly, but when that reaches the top and should stop the refill process, nothing happens and it continues to fill for a while longer until the water level reaches the overflow and about 20 seconds later with water trickling down the overflow it eventually stops filling.

I'm not sure of the exact parts fitted but the inlet valve looks very similar to a Siamp Compact 99T BP and the flushing valve looks like an Optima 49.

I've adjusted the height of the float, which I believe should set the max water level and I've made sure that it is at least 20mm below the overflow level, but i doesn't make any difference. I can even position the float at the lowest adjustment and the water still fills up to the overflow.

The float is being correctly lifted by the water, but it just doesn't cause the refill to stop. I have even tried lifting the float mechanism by hand immediately after flushing and even that doesn't seem to cut the water off, until it reaches the overflow.

Very occasionally the water does cut off before it overflows, but it is rare and I can't figure out what is making the difference.

I'm assuming something is broken, but I can't figure out what.

Any plumbers able to shed some light on where I might be going wrong?
 
It is usually just a bit of shgrit stuck on the valve seal that lets the water flow through. A new seal might be able to close over it but an old one isn't as flexible so a gap is left.

Replace the whole valve or just the seal whichever is easiest/cheapest to source.
 
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