Leaking Low Level Flush Pipe

21 Feb 2021
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United Kingdom

Hoping for some help please.

I discovered a swashing under the bathroom lino, only to take it out and find a swimming pool underneath.

The wooden board on top of the floorboards under the lino has expanded the top layers due to the water ingress.

After investigation of the built in cistern it appears the flush pipe into the back of the toilet has been leaking for some time.

The flush pipe itself travels slightly uphill into the back of the toiler - is this how its supposed to be?

Should it be level or slightly down into the back of the toilet so some of the water doesnt go backdown the flush pipe after a flush which seems to be happening?

I have fitted a new Flush Pipe Connector
(https://www.toolstation.com/flush-pipe-connector/p28142) over the flush pipe into the toilet but its still leaking although not as bad - mainly after the flush cycle finishes there is some run off due to the pipe being uphill that comes out past the flush pipe connector even though it is fully in.

I assume the plumber who installed it cut the flush pipe too short and possibly fitted the cistern too low (hence the uphill path to the toilet).

What's the best way to ensure the leak stops?

How do flush pipes seal - (If I get a long enough pipe would that stop water going back past the flush pipe connector?)?

I assume the flooring will have to be taken up and replaced and mould checked for under the floorboards and joists?

Any help appreciated,
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Is that flush cone rubber ? Some are made from a fairly rigid plastic ,and in my opinion are junk. Use a black rubber flush cone.
The flush pipe should run slightly downward into the pan ,however if the seal is good ,there shouldn't be any leakage. If anything ,the vertical section of the flush pipe is too long ,if the horizontal part is uphill to the pan.
Anyone's guess about the flooring damage, would need investigating.
Thanks Terry,

There was a black rubber one in there before but it had come 2/3rds out and was hard so think it had had its use as wouldn't go back in.This one I am not sure of the material but its medium hardness in that you can bend the bit that goes into the toilet a bit.

How is the flush pipe meant to connect to the toilet? Does it push into a smaller hole within the bigger hole and sit tight there?

I assume regardless of the connector type or angle of the flush pipe it shouldnt allow water back out of it?

I think the flush pipe is too short to go too far into the back of the toilet however.

The vertical part of the flushpipe is quite short as in about 10cms if I was to guess so I cant shorten it anymore. Interestingling it just slides off what looks like a wider part coming out of the cistern that goes into a smaller part and then the flush pipe above the bend fits onto this.

Thinking back there was a square of wood or tile sitting next to the waste pipe so not sure if this was behind the cistern pushing it out so may have to look at something behind the cistern to see if that levels out the flush pipe.

I should also add that where the water has leaked/is still leaking a bit it has managed to find its way into the smoke alarm below and I think possibly the mains wiring as the alarms were all going off randomly until they were disconnected (water was in the alarm).

I have shut them off at the breaker as there was a buzzing and cracking sound coming where I think water has got into the alarm base on the ceiling and into the part where the wires clamp to the alarm base so hoping once fixed it will all dry out ok and the wiring ends will be ok.

Amazing how much damage and hassle a water leak can cause
Any idea of the best flooring to put down to replace what i may have to replace to sit on top of floorboards?
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The flush cone is fitted to the end of the flush pipe ,with none of the pipe protruding . The flush cone and pipe when inserted into the pan should be a tight fit. The full length of the cone should be inserted until it is flush with the outer surface of the pan inlet.
Didn't really follow your description of how the vertical part connects to the cistern ,usually there is a nut and seal that connects it to the flush valve.
A lot of these thin plastic cisterns are flimsy , anchored at the top with a few screws and move easily ,swinging you could say. It's common to have to support the cistern and flushpipe with brackets or timber.
What currently sits on top of the floorboards ?

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