Well, that was exciting ...

[Tim Streater]

... being called down stairs urgently by SWMBO to find that the downstairs loo cistern had a large crack running from just around the side at the bottom and diagonally up across the front face, all the way to the top.

The crack starts small at the bottom/side and is a few mm wide at the top. It doesn't start at the spot where the fill pipe comes in, either.

Luckily the plumber has fitted an isolator valve as part of all the new work here so that and a quick flush quieted the deluge.

Anyone seen this sort of sudden catastrophic failure before? In a f***ing *loo* cistern??

[PeterC]

Had there been a sonic boom this morning?

[Chris K]

Yep, on a 20 yr old cistern spontaneously cracked.

Not called downstairs though, first phone call on turning the 'phone on after landing in the US :-)

IIRC, looked like it was the retaining screws fastening it to the wall rusting and putting pressure on the hole. There is a reason why brass screws should be used here. Seems like a rectangular cistern after firing has a lot of internal stresses waiting to be relieved.

Chris K

[The Natural Philosopher]

Tis possible. Many stresses are fired into ceramic. And a hairline crack can hide under the glazing.

Or an overtightened flush mechanism finally crack something under temp changes.

[Ret.]

That happened to a loo cistern in our bathroom some years ago. The crack didn't open up as much as yours, however, and I accomplished a repair by emptying the cistern and covering the crack on the inside with fibre-glass matting and resin. That repair lasted until I replaced the bathroom a couple of years later.

-- Kev

[Chris Hogg]

It's exacerbated if the loo/cistern isn't fired quite to full vitrification as they're supposed to be, i.e. still has a small amount of residual open porosity. Over time (years), water diffuses into the pores in the walls of said loo/cistern and causes expansion, resulting in stresses and eventual cracking. From time to time, sanitaryware manufacturers get 'outbreaks' of this fault, but it doesn't reveal itself for many years after production.

[Alan]

In message , Chris K wrote

I've seen some "brass" screws rust :( (crap screws with some yellowish coating, but sold as brass)

These days I use stainless steel screws for bathroom and kitchen environments. For a one off job for yourself the cost is not prohibitive.

[The Natural Philosopher]

Zn or Cd plate + passivated

Good idea. FFFR

[Chris Hogg]

If I ever want to buy brass screws, I take a magnet with me....

Agreed, also for outside use, as we get a lot of salt in the air where we live on the coast, and even zinc plated/galvanised screws rust in a year or so.

[Tim Streater]

Going back to my original post, thinking about it there is just a possibility this is my fault. About four months ago there was a problem with the mechanism, and when the cistern filled up the valve didn't shut the water off. The overflow then was rushing down the toilet bowl, prolly had been for some hours. It's one of there close coupled jobs.

Not knowing how to get the lid off this thing, my first thought was that it was just a press fit so I tried to lever it off. No joy, so then I applied some *thought* and unscrewed the flush mechanism that sat in the middle of the lid. That did it.

But perhaps that levering about was enough to make it go ping! today.

[The Medway Handyman]

Or a vindaloo last night?

[Chris Hogg]

If it was internally stressed, and it sounds as though it was, given the size of the crack, I would have thought it would have pinged at the time you levered it, if you'd damaged it in some way.

[Tim Streater]

Nothing so interesting :-(

[Derek G.]

No, a sonic bum.

Derek G.

--

This Looks like Finito Ruperto.

[Hugo Nebula]

Yes. In my mother's house a couple of years ago. The cistern had cracked (at the rear against the wall) overnight allowing the water to flow unimpeded for several hours onto the top of a lath & plaster ceiling over the kitchen, and then onto a quarry tiled kitchen floor. Not pretty.

We put it down to the cistern being attached too firmly to the wall not allowing for any slight movement.

[Tim Streater]

Thanks. To be borne in mind when we get a replacement installed.