Hot-fill toilet cistern . . .

Apr 16, 2023 Last reply: 3 years ago 19 Replies

I recently fixed a leaking toilet for a friend (the supply-cistern flexible pipe had loosened) and it's connected to the hot water. This isn't warm-next-to-hot pipe hot - it's a constant supply of 60C water.



My friend says he's not bothered - the toilet's not used much, a guest en suite. It's been that way since it was fitted - about 5 years ago, and the leak is only recent. But I'm not so sure it's a good idea to have hot water around the flush mechanism etc.



Any opinions?


What is there to say? The downside is as obvious as it gets

When cooling, tepid water breeding ground for bugs. Legionella. A toilet produces an aerosol of droplets when flushed, just like a shower. I wouldn't trust it.

As long as the water after a fill gets above 50C then any legionella should be largely decimated. The cool-down will only take hours and then finally get to close room temperature.

The cool-down time is the critical aspect here, but also the time at which it stays at room temperature. This will of course be independent of whether the cistern is hot or cold filled.

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note that both patients were immunocompromised and contamination of toilet water was not common.

It's possible his central heating is pumping over and venting into a loft tank, and the cistern feeds from it so fills with hot water. I read of a case involving this phenomenon - the plastic loft tank got so hot that it collapsed and emptied over the couple sleeping in the room below killing one of them and seriously scalding the other - so you should probably check it out.

There shouldn't be any connection between the CH and a toilet feed. Pumping over with hot water should only be to the dedicated CH expansion tank which only feeds the CH system.

If there is a connection that the CH water that circulates outside of CH then there are much more serious consequences than just a toilet filling with hot water.

A CH header doesn’t feed the cold taps. Also, the tank that collapsed was the HW header tank that was heated due to a failed immersion thermostat causing the CH cylinder to grossly overheat.

Tim

It would make me wonder what other weird plumbing exists in the property.

No you don't want that, apart from anything else water heating should be costing money, so why have it. Chances are the two pipes are adjacent to and a fix with all the water off should not take very long given the right pipes and fittings. Good luck with the air locks though! Brian

No indeed, though that particular hazard is very very rare. Why waste heated water which will just sit there and go cold most of the time anyway, unless its a secret way to heat the loo!

Brian

There was a similar event where a child was killed. A stuck thermostat on an immersion heater kept heating the hot water cylinder and caused hot water to rise into the plastic header tank. After that they required immersion heaters to have both a thermostat and an independent over-temperature trip.

Has been used as a solution to condensation on the cistern

Add an upward facing jet to the outlet and you can remain seated when it flushes.

There is or used to be a Japanese toilet for the disabled that does just that, IIRC.

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we need more information.....

We have nothing to go on...... :-)

Exactly, that is why the stats now must have a trip.

No loft tank apparently - direct fed from a cylinder 2 floors below.

Quite - it's a large back to brick Georgian listed house. Apparently the original plumber had a breakdown, and more than one other contributed to finishing off whatever it was he started.

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