Toilet flush pipe stays full of water

14 Mar 2009
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United Kingdom
Hi all.
I'm trying to fix an issue that started as a leak between the toilet pan and the flush pipe but has now become confusing.
Standard floor mounted toilet pan.
Small hidden dual flush cistern within the built in cupboard behind the pan.
I've replaced the pan/pipe seal and stuffed the pipe into the new seal. I just refitted the cistern into the cupboard behind the pan, turned on the water at the isolator, and did a trial flush.
Turns out the flush pipe wasn't very well sealed into the bottom of the cistern and I felt a few drips, so decided to take the cistern back out of the cupboard and try again.
Having done that I've discovered that the flush pipe is now full of water. It's not emptying out into the pan, which is why there was so much standing water that could leak into the cupboard past the old pan seal.
Why would the pipe not be draining into the pan? Does this suggest a blockage inside the pan? Or is this normal?
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You say full of water, completely full? Did you push pipe too far in?
Thanks for the reply. I'm sure the pipe isn't in too far; I'm not even sure it's in far enough!

The water level in the pipe is perhaps 2cm below the level of the pan rim, and steady at that level.
Didn`t leave something in the pan to stop a drip did you?
Normal L shaped flush pipe?
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No, I didn't insert anything into the pan to stop the leak or absorb the water before I put the new seal and pipe in. The loo has been dismantled for about a week while I got round to this job with the new seal so it had chance to dry out.
Yes, it's a normal right-angle flush pipe.
If I wiggle the pipe left/right and up/down the water doesn't start draining into the pan.
It's almost as though the pan has a non-return flap/valve that's putting a bit of resistance in the way of the water draining in through gravity.

Your questions make me think this isn't normal though, which in itself is helpful!
Ok, is the horizontal section of the flush pipe pointing slightly upwards then?
There's enough flex in the pan seal (flush cone?) that I can tip the pipe up and down quite a bit. Even with the open end high the water doesn't run out of the pipe into the pan.
Sending photos of my toilet parts to strangers on the Internet on a Friday night. Are you lot the ones my mummy warned me about? ;)


Looking down into the flush pipe:

The full pipe, already dripping again at the flush cone!

Rotated the pipe elbow and drained ~300ml of water out?

On Tuesday, before I replaced the flush cone, I took a photo with my endoscope. Does this 'wall' of porcelain inside the pan suggest it's designed to hold the water in this way for some reason?

Grateful for the replies and for any help you clever chaps can offer.
I did have a toilet once where parts from the syphon came off and got stuck in the toilet inlet where the flush pipe goes. You might need an endoscope to look further in.

You're right - I need to take the pipe and cone out and have another look with my endoscope. The cistern has a bit of light limescale but nothing that would block the flush pipe. I have a funny feeling the pan was just designed this way.

Given that even the new seal is leaking I guess the pan hole needs cleaning up so I'll do that at the same time. Access is awkward and I've never been much of a gynaecologist.
You can't have enough fall on the flush pipe ,if that amount of water is being held. With regard to the leak ,pack in-between the fins of the flush cone with plumbers mait putty ,it won't leak anymore !!

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