Toilet cistern problem - second post (Iwould appreciate a reply from Buildersmate if he's around)

[MichaelZZ]

Sorry if I didn't make myself clear on my earlier post. The thread seemed to take a wrong turn! The toilet bowl is not overflowing nor is it blocked. Anything in the toilet bowl is discharged in the normal manner, no problem. The problem isn't with the bowl, it's with the flush mechanism apparently not behaving itself - especially when the shower or wash basin tap is turned on. There is no problem with removing the top of the cistern. The problem is that the cistern doesn't shut off, indeed it seems to "auto-flush" when the shower is turned on.

The cistern's internal overflow appears to be doing what it's designed to do and that is to direct excess water into the toilet pan.

[winkyridg]

Do you need to adjust the Valve/float so it doesn't take in as much water, normally just a screw that needs turning with a small flat headed screwdriver, seems a little weird that it flushes when the shower is on.

[The Builder]

You just couldn't make it up Michael ;o) Strange set of circumstances.
I guess that, first of all, the mains pressure is very poor. When one valve is open, everything else is starved............ maybe

Apart from that, I would replace the valve coming in to the cistern. It sounds as though it's bouncing, and can't make its mind up whether it's shut off or not (that's possibly a float problem.) The float may be fouling something. In which case, as the water level goes up and down, the float jiggles about and lets in more water. The shower and basin, I guess, are simply causes the water pressure to vary....... thus "confusing" the cistern valve.
This is all speculation, but there is no other interconnection between the various appliances.
If the float is sticking somewhere, it's an easy job to adjust it, or replace.

[The Builder]

^^^^ "causing" ^^^

[MichaelZZ]

Many thanks, TB.
You're quite correct, the mains pressure is a bit on the low side. Also my daughter lives in a hard water area so I suspect a bit of limescale or similar may have got into the inlet valve. I have been promised a movie clip so that I can see what's happening. (Just as soon as the camera battery is charged up!)
Thanks again for your most helpful comments.