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weak toilet flush

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Boilersuit

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My toilet flush is very weak & can't really even flush a few sheets of toilet paper away.
A syphon flush, not a flapper.

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.

Nobody in the house did anything that might have caused this.

Thought it might be the diaphragm in the syphon. When I took it out it looked fine, but I replaced the entire syphon anyway (this is the new one I put in).

After re-fitting everything with a brand new syphon & testing the flush, it's still as weak as it was when I started. Still makes the hollow sound.

I've tried adjusting the levels on the syphon to fit the water level etc.

I've tried cleaning the holes under the rim of the toilet that feed water into the bowl. They weren't blocked but I gave them a scrub with a wire brush anyway.

Nothing works.
The pipes that carry the waste away from the toilet are fine - we can flush by throwing a bucket of water down.

Can't find any other suggestions online about what this might be. Anyone got any thoughts?
 
Then something has been changed or done to it else it wouldn’t change originally
 
ShaunCorbs said:
Then something has been changed or done to it else it wouldn’t change originally
Click to expand...
Yeah I just can't figure out what was done to it.

It's an old enough toilet & gets a lot of use. There's a good few of us living here & only one toilet. Could it be something wore away cos of use?
Like I said I did install a completely new syphon, along with a new donut washer. Is there another part of the cistern that might be affecting this?
 
Not in a short space of time and would slowly get worse

No other than the water height in the cistern or a blocked toilet but your water level in the bowl would rise
 
Undertrained said:
The float valve (inlet valve), especially if it’s catching on the wall of the cistern or the syphon. If you’re unsure post a photo of inside of cistern when full of water.
Click to expand...
The float valve doesn't catch on the wall but it's a pretty close fit alright.
I've slightly overfilled the cistern (used a bucket of water) then flushed & its not much better.
IMG_20210911_132310.jpg
 

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The only other thing is the siphon threaded part is too long but that wouldn’t of caused your old one to just not work as good overnight
 
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
 
If we presume that it's not the syphon which is a valid assumption because this problem has persisted with two different syphons and the issue started when using a (previously) known good syphon, then it must be something else.
The water flow after the syphon must be restricted, so it's either the rim holes or the water channels leading to them.
Have you ever used one of those 'blu loo' type cistern blocks or something similar? They can leave debris in the water channels in the pan.
If it's the rim holes the problem would have been slow and progressive as the holes slowly became blocked.
You say it was an overnight thing so there must be a physical blockage.
The cistern needs to come off and you need to look down the water entry hole in the pan and into the channels to the rim. I have an endoscopic camera that comes in handy at times like this, maybe find out if you know someone who has one. Also something like a dentists mirror could be used to look down the beginning of the channels.
The channels can start quite wide but get narrower towards the front of the pan, a blockage on one side would have a big impact on the performance of the flush.
 
JCplumb said:
If we presume that it's not the syphon which is a valid assumption because this problem has persisted with two different syphons and the issue started when using a (previously) known good syphon, then it must be something else.
The water flow after the syphon must be restricted, so it's either the rim holes or the water channels leading to them.
Have you ever used one of those 'blu loo' type cistern blocks or something similar? They can leave debris in the water channels in the pan.
If it's the rim holes the problem would have been slow and progressive as the holes slowly became blocked.
You say it was an overnight thing so there must be a physical blockage.
The cistern needs to come off and you need to look down the water entry hole in the pan and into the channels to the rim. I have an endoscopic camera that comes in handy at times like this, maybe find out if you know someone who has one. Also something like a dentists mirror could be used to look down the beginning of the channels.
The channels can start quite wide but get narrower towards the front of the pan, a blockage on one side would have a big impact on the performance of the flush.
Click to expand...
I have tried to clean out the channels that go into the pan, used a narrow wire scrubbing brush & pushed it til I could see it from the water entry hole.
Never used any of those blue loo things either.
I'll try what you said next time I take off the cistern. Don't think I'll be able to get an endoscopic camera or anything like it but might try something with lights & mirrors!
 
ShaunCorbs said:
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
Click to expand...
ok you mean where the siphon connects to the pan! Right that's a good lead. I'll try taking it all apart & checking, I definitely didn't notice if it was too long or anything like that. Thanks
 
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.
 
Boilersuit said:
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.
Click to expand...
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.
 
Last edited:
Ric2013 said:
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.
Click to expand...
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!
 
Chuck said:
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.
Click to expand...
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
 
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!
 
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.
 

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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.
 
snowhead said:
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.
Click to expand...
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.
 
Cut one thread off the bottom of the siphon worth a try
 
Try pouring a bucket where the pan hole is eg the cistern / siphon goes on
 
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