Help my toilet cistern is cracking

[Melter]

Nightmare. I've been doing some work on the bathroom and installed a new basin a couple of days ago. All of a sudden the toilet cistern is breaking up so I've turned the water and will be going on a hunt for a new cistern.

I've a question though about what's caused this. I had to disconnect the new basin because it's a sit-on type on a unit right next to the cistern. When I disconnected the hot supply there was a quick release of air/pressure and the crack in the cistern widened. Is it likely that something I've done/not done has created too much pressure and cracked the cistern or is this just a bad coincidence?

 

[big-all]

does the crack start or finnish at a hole is there any chipping
along the crack line when you get it off see how clean the
edges of the crack are

probably just a flaw thats given way when youve leaned on it

big all

 

[Melter]

Sorted. Found a replacement cistern at Wickes so no altering of pipework to get things to fit. Installed and things seem fine...touch wood . Quite pleased as I've never had to tackle something like this before. I'll try to stop asking so many dumb questions (see other posts) .

 

[big-all]

glad you got it sorted

sometimes its just reasurance that we need
we are not going mad are we

big all

 

[Melter]

Now have a leak that I can't stop. It's not even a drip just the slightest amount of water slipping past the seal but over a few hours can still make a little puddle on the floor. The new cistern came with one syphon washer to go inside the cistern so I've added another seal to the outside with no improvement. I've added ptfe to the pipe thread just in case. I did wonder if I was over tightening the back nut so I tried adding turns once the cistern was full but no luck. Any other suggestions please?

 

[ArtfulBodger]

Buy some LSX from a plumbers merchants and coat the washer and the underside of the backnut and try again. Also, you can check for leaks before fitting by just filling it with water and placing it over a sink or basin.