weak toilet flush

[Chuck]

Up until a few days ago it worked perfectly, then the flush just started being really weak. Doesn't flush toilet paper at all.
Water comes out & the cistern empties, but the water comes out so weak that nothing flushes away.

The water makes a slightly different sound now when it comes out of the cistern into the bowl - I can hear a hollow sound now coming from the cistern, as if there's not enough water or too much air somewhere & it's kind of struggling.

The diaphragm would be my guess. My second would be a crack in the the siphon that is letting air suck in; enough to reduce the flow and change the sound but not enough to completely stop it working.

Did you fit a 'dual flush' replacement siphon (I can't be sure from the picture) ? If so, check that the tank is fully emptying when you flush. If it stops halfway you may be operating it incorrectly or it may be faulty.

 

[Old UKPF 123567]

No the thread part after the nut being too long and not much gap left between it and the casting in the pan side might be worth cutting an inch off to prove it if it’s miles past the donut washer

OK I'm fairly sure this thread isn't sticking out too far. But what do you think?

 

[Old UKPF 123567]

I once experimented A friend of mine once experimented with what would happen if a bit of toilet paper went past the flush valve and into the close-coupled pan. The toilet at home has never been (quite) the same since as I never did he never did quite get the dregs out of the waterways of the pan.

I'm wondering whether a family member may have tried the same experiment I tried a friend of mine tried, or whether another small object may have been lifted up through the siphon and is hidden in the pan waterways somewhere. I know you've looked in the top of the pan but it may not be enough.

Sorry to hear about your friend & their toilet.
I'm going to try cleaning out those waterways today. This morning there was a little bit of debris in the cistern alright - probably caused by me opening the top of it a lot the last few days!

 

[Deleted member 120897]

OK I'm fairly sure this thread isn't sticking out too far. But what do you think? View attachment 63588

Thread looks ok to me.

 

[Old UKPF 123567]

The diaphragm would be my guess. My second would be a crack in the the siphon that is letting air suck in; enough to reduce the flow and change the sound but not enough to completely stop it working.

Did you fit a 'dual flush' replacement siphon (I can't be sure from the picture) ? If so, check that the tank is fully emptying when you flush. If it stops halfway you may be operating it incorrectly or it may be faulty.

Diaphragm is fine. It was fine in the first syphon, it's fine in this one.

I can't see any cracks in the syphon. It's brand new so I really hope there's no cracks.

It is a dual flush siphon alright, this one PRO-ULTRA Fluidmaster® PRO Universal Dual Flush Syphon - Fluidmaster - https://www.fluidmaster.com/united-kingdom-products/pro-ultra-fluidmaster-pro-universal-dual-flush-syphon/
Have tried a few settings on it, but the tank does not actually fully empty when I flush - might be something there I'll look into

 

[Old UKPF 123567]

I've tried cleaning out the jet channel that goes from the cistern into the toilet pan (there's only one). It seemed fine, not a huge amount of sediment coming out of it & no problem getting a wire to pass all the way through it.

I've re-installed the syphon again.

Nothing's working! At the end of my tether here tbh, might just call a professional ¯\(ツ)/¯ thanks for all the help guys!

 

[Chuck]

I can't see any cracks in the syphon. It's brand new so I really hope there's no cracks.

I meant in the original. A crack or split seam would fit the symptoms and explain the sudden onset.

 

[Old UKPF 123567]

I meant in the original. A crack or split seam would fit the symptoms and explain the sudden onset.

Ah fair. Well I got a replacement syphon & still have the same problem

 

[Deleted member 120897]

What about trying removing the cistern again, and running some water into the pan inlet where the syphon would sit, see if this helps with anything?

 

[Old UKPF 123567]

Hope it's ok to resurrect this thread!
I left this be for a while cos of life commitments etc. But I'm back at it now.

I noticed the syphon pump actually pulls in water as it is flushed. You can see it gurgling up,see the video.
I can't figure out why it does this, but it definitely is part of the problem as it means the water doesn't get pushed strongly up & over down the flush pipe into the bowl.

Just a recap this is my THIRD new syphon that flushes weakly like this, it's the more expensive fluid master one.

 

[snowhead]

In a word,,, Rubbish.
The water should move far quicker than that.
How far above the bottom of the cistern is syphon?

That demonstration is giving the impression that the flush pipe is filling up and not allowing the syphoned water to pick up speed, assuming there is clearance under the syphon to allow the water to get into it.

 

[Old UKPF 123567]

In a word,,, Rubbish.
The water should move far quicker than that.
How far above the bottom of the cistern is syphon?

That demonstration is giving the impression that the flush pipe is filling up and not allowing the syphoned water to pick up speed, assuming there is clearance under the syphon to allow the water to get into it.

It's about a quarter of an inch above the bottom of the cistern right now (and in that video). It's an adjustable-height syphon so I have tried it at a few different heights. Does the same whatever height I set it to.

 

[ShaunCorbs]

Cut one thread off the bottom of the siphon worth a try

 

[Old UKPF 123567]

Cut one thread off the bottom of the siphon worth a try

Just tried that. Reconnected everything & nothings changed. Flush still very weak, syphon still sucking in water

 

[ShaunCorbs]

Try pouring a bucket where the pan hole is eg the cistern / siphon goes on

 

[Old UKPF 123567]

Try pouring a bucket where the pan hole is eg the cistern / siphon goes on

Did this a good few times. The water goes through like you'd expect

 

[ShaunCorbs]

Ok remove the siphon from the carrier eg undo the red clip and lift the right half off and pour a bucket down the tube

 

[Old UKPF 123567]

Ok remove the siphon from the carrier eg undo the red clip and lift the right half off and pour a bucket down the tube

OK did that. Not sure what I'm looking for tbh.
The water comes into the bowl in a fairly weak stream, but that could be because I'm just pouring a bucket

 

[Chuck]

This is turning into quite a saga.

Have you tried taking the cistern outside and testing the siphon's operation with a bucket under it instead of the pan? This would at least tell you whether the issue was with the cistern, which I think is less likely after you've tried three siphons, or blocked channel(s) in the pan, which is where my money is.

 

[Old UKPF 123567]

This is turning into quite a saga.

Have you tried taking the cistern outside and testing the siphon's operation with a bucket under it instead of the pan? This would at least tell you whether the issue was with the cistern, which I think is less likely after you've tried three siphons, or blocked channel(s) in the pan, which is where my money is.

I'm so sick of this toilet by now!

So I haven't tried that exact thing, I'll give that a shot soon & report back.
I'm starting to think it could be blocked channels too, but also have been poking at them a lot & not noticed any major blockage.