Toilet won't stop running after flushing and I can't get into the cistern (rented house)

[MirandaWest]

Toilet is continually running after flushing and due to how the toilet is fitted you can take the front part off to get to the cistern but not get into it as the plastic part is too high to get your hand in (is fitted under a marble looking surface.

Is this something it would be reasonable to call a letting agent or alternatively can anyone suggest something? Running a tap has worked before but isn't working now and I'd prefer not to see the water literally running away before me

It sounds too simple to work but whenever I've had that problem I've found the simply pushing the flash button or lever again will make it stop.

It's something that you need to get into the cistern for I'm afraid. You need to get the top off. You can google fixes but it may need a new valve or washer.
If you are in a rental property then it would be fair enough to get the agent/landlord to sort it out.

Yes try pushing the flush quickly a few times.

Is there an accessible valve on the pipework to the cistern that you can turn off once the cistern is full until you next need to flush it?

Thank you everyone - it stopped after a couple of hours but started up again not long after I flushed the downstairs toilet. Have tried flushing again and sadly it just makes it happen again. The cistern itself doesn't have a top but there is a work surface type thing over it and I have no idea how you'd remove that. If I owned the house I think I'd need to call a plumber as I wouldn't be able to do it myself. Just hoping the letting agent can send someone out relatively quickly as would prefer not to have this indefinitely. Plus shower only doing a trickle when toilet doing this.

I'm afraid I don't know what valves there might be on the pipe work to the cistern - am worried if I try fiddling things would go more wrong. Was sounding like someone being sick before which was a bit unnerving.

Hopefully it will stop at some point tonight...

Definitely call the Letting Agent and stress that it is urgent. My tenants call the Letting Agent for everything, minor as well as major. I have got British Gas cover for the rental property and most plumbing, electrical and gas problems are covered by that - the tenant just calls British Gas direct.

Look at the water pipe that fills the cistern up. Is there a small valve, looks like a flat head screw on the pipe? If there is, turn it 90 degrees (so the line goes across the pipe rather than parallel) this stops the water going in - very easy to put back when you want it to fill, and don't worry you can't break anything doing this.

..but even if you have a temporary fix, contact the agent to report it and ask for something to be done.

the point of a rental is that you don't pay to fix things like this, that's the landlord's responsibility.

BTW love the nickname. :-)

what you are looking for is an isolating valve like this (but I hope not such cheap rubbish). Observe that in the picture the slot in what looks like a screw head points along the pipe. If you turn it so it points across the pipe the water will stop. It doesn't matter which direction you turn it, or how many times. It is not really a screw and will not screw out.

With luck the service valve will be in the 15mm supply pipe which goes into the side or bottom of the cistern

If you are very lucky it will have a valve with a plastic quarter-turn lever.

meanwhile tell the agent you need a plumber. It is a common problem.