• Welcome to PlumbersForums.net - The international free plumbing advice forum. Professional plumbers sharing advice with fellow plumbers and DIY alike. Register for free today! - Checkout the Plumbing Advice forum and then our Plumbing Videos area which still needs populating.

From the United States of America? - Checkout our specific plumbing forum for you:USA Plumbing Forum

Discuss Siphon continues to leak from lowlevel WC. in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

Messages
124
I am having a real problem with a leak that commenced a couple of months back re my folk’s WC. It is a straightforward Armitage Shanks low-level type (relatively old) that started leaking underneath the WC from the siphon connection. I took the thing apart and it appeared that the siphon sealing washer had become rather brittle over time. When reassembling with a new washer it became clear that the outlet on the cistern is substantially larger (58mm diameter) than the diameter of the siphon’s threaded tail (45mm diameter). Just about all similar cisterns that I have dealt with previously have a more snug fit with siphon.

Despite several attempts I could not get the connection to seal though I was not surprised given the gap between the threaded section and the cistern outlet. What was more bemusing was how the original connection had ever held in the first place. Anyway I chose to fill the gap with a roll of Plumbers’ Mait and reconnect. This sealed the connection perfectly fine. I checked this over the next couple of days to find that it was completely dry.

A couple of weeks later I received a call from the folks to say that there had been a substantial leak from cistern and he had turned off the service valve and sponged out the cistern. This left him having to use a bucket until I could return – not a total crisis as this is a second WC in the folk’s home.

So upon engaging with the WC once again I checked out the connection and removed the PM from the failed joint. I had brought a couple of alternative siphons and several different washer types. One thing I noticed was that the flange area of the fitted siphon was slightly smaller than that on the other siphons. So I decided to change this for a wider flanged Dudley 2-piece. Among my alternative washers I had what I refer to as a ‘throated washer’ which rather bulkier than the standard sealing washer but managed to seal the said area nicely.

I reassembled and tightened the backing-nut on the joint by hand and reconnected the flushpipe. I then filled the WC and gave it a flush. A little water penetrated from the joint but I tightened this gently with a wide-jawed spanner. The joint remained dry and could be flushed without problem. This successful state of affairs seemed to continue for a couple of days but weirdly the leak infuriatingly returned. A further gentle nip with the spanner prevents the leak for a while but at some stage it reappears.

Does anyone have any ideas as to what I could do here, please? Maybe it would be worth running a few layers of PTFE around the siphon thread? If nothing else works then I reckon I may have to use silicone to make the seal but that is a bit 'last ditch'.

Also why do the siphon manufacturers cut away a section of the circular flange? Though I have never had a problem with fitting siphons previously it does seem likely to minimise the sealing area twist siphon and cistern?

Note: The photograph is a slightly larger version of the washer that has been fitted.


Siphon issue.png20191225_135656.jpg
 

king of pipes

Esteemed
Plumber
Gas Engineer
Messages
4,921
That's plumbing for you 9 times out of ten your method would of been successful then comes that one job whatever you seem to do that drip comes back to haunt you, I always ptfe the syphon threads a smear of silicone would not hurt as a last resort but it's not good practice as it can make rubber seal go out of shape as you tighten . All the best Kop
 

centralheatking

Esteemed
Plumber
Messages
1,242
I am having a real problem with a leak that commenced a couple of months back re my folk’s WC. It is a straightforward Armitage Shanks low-level type (relatively old) that started leaking underneath the WC from the siphon connection. I took the thing apart and it appeared that the siphon sealing washer had become rather brittle over time. When reassembling with a new washer it became clear that the outlet on the cistern is substantially larger (58mm diameter) than the diameter of the siphon’s threaded tail (45mm diameter). Just about all similar cisterns that I have dealt with previously have a more snug fit with siphon.

Despite several attempts I could not get the connection to seal though I was not surprised given the gap between the threaded section and the cistern outlet. What was more bemusing was how the original connection had ever held in the first place. Anyway I chose to fill the gap with a roll of Plumbers’ Mait and reconnect. This sealed the connection perfectly fine. I checked this over the next couple of days to find that it was completely dry.

A couple of weeks later I received a call from the folks to say that there had been a substantial leak from cistern and he had turned off the service valve and sponged out the cistern. This left him having to use a bucket until I could return – not a total crisis as this is a second WC in the folk’s home.

So upon engaging with the WC once again I checked out the connection and removed the PM from the failed joint. I had brought a couple of alternative siphons and several different washer types. One thing I noticed was that the flange area of the fitted siphon was slightly smaller than that on the other siphons. So I decided to change this for a wider flanged Dudley 2-piece. Among my alternative washers I had what I refer to as a ‘throated washer’ which rather bulkier than the standard sealing washer but managed to seal the said area nicely.

I reassembled and tightened the backing-nut on the joint by hand and reconnected the flushpipe. I then filled the WC and gave it a flush. A little water penetrated from the joint but I tightened this gently with a wide-jawed spanner. The joint remained dry and could be flushed without problem. This successful state of affairs seemed to continue for a couple of days but weirdly the leak infuriatingly returned. A further gentle nip with the spanner prevents the leak for a while but at some stage it reappears.

Does anyone have any ideas as to what I could do here, please? Maybe it would be worth running a few layers of PTFE around the siphon thread? If nothing else works then I reckon I may have to use silicone to make the seal but that is a bit 'last ditch'.

Also why do the siphon manufacturers cut away a section of the circular flange? Though I have never had a problem with fitting siphons previously it does seem likely to minimise the sealing area twist siphon and cistern?

Note: The photograph is a slightly larger version of the washer that has been fitted.


View attachment 42036View attachment 42037
You have not made a mistake, your approach is what we all do as KOP says. So off you go again we have all been here. However its really essential you clean off all the old crud stuff before doing this.
The flange looks ok aswell, it should be soft rubber type not hard ...cant tell from picture. chking
 

Ted808

Plumber
Gas Engineer
Messages
343
This is so annoying! I feel for you! I would put some ptfe around the thread, but the seal is betwwen the flange of the siphon and the cistern, so it's down to the washer- have a look at www.toiletspares - I've found it to have the most unusual spares and help identifying what you need. In a way, you're lucky it's at your parents, and they have a second toilet. The thing is plumbing is much more difficult than people think. Do let us know how you solved it in the end. I've also wondered about that missing bit of some washers? what's that all about?? Good luck mate.
 

ShaunCorbs

Staff member
S. Mod
Plumber
Gas Engineer
Messages
27,661
Normally use a plastic 1.5” washer on both sides eg top side of the push button siphon and just before the nut on the cistern side normally works well
 

Best

Esteemed
Plumber
Messages
9,999
Cisterns are often misshapen where the siphon meets them and Armitage often were.
And the seal washers have very little give in them.
Silicone on the washer will seal it for you. It might seem a bodge, but it works.
Worry about sealing it on the internal joint and don’t rely on attempts at the outer joint
 
Messages
124
Thanks very much for your input, guys. Actually, I did not make this clear but my method of using silicone requires replacing the rubber sealing washer with a plastic equivalent and applying silicone to each side. Then the whole lot cures (hopefully) sealing the lot. Not great practice, I know, but it may ultimately be the best option.

Weirdly, for the moment, the connection appears to be dry so I’ll monitor it over the next couple of days and maybe try reassembly with PTFE or failing that with silicone as described. Will be buying a box of straws to clutch as well.

Shaun: Why do you refer to it as a 1.5” washer? It OD is 70mm and ID is 45mm. To me 45mm is around 1.8” yet I can see you are clearly not alone, here, hence:
Whilst I am not indulging in bog-bodgery I have been trying to install Windows 10 onto my folk’s museum piece Inspiron. This has provided further excitement and some additional chaos so if I do not reply promptly you will understand why. :mad:

Thanks, again. :)
 

Best

Esteemed
Plumber
Messages
9,999
Thanks very much for your input, guys. Actually, I did not make this clear but my method of using silicone requires replacing the rubber sealing washer with a plastic equivalent and applying silicone to each side. Then the whole lot cures (hopefully) sealing the lot. Not great practice, I know, but it may ultimately be the best option.

Weirdly, for the moment, the connection appears to be dry so I’ll monitor it over the next couple of days and maybe try reassembly with PTFE or failing that with silicone as described. Will be buying a box of straws to clutch as well.

Shaun: Why do you refer to it as a 1.5” washer? It OD is 70mm and ID is 45mm. To me 45mm is around 1.8” yet I can see you are clearly not alone, here, hence:
Whilst I am not indulging in bog-bodgery I have been trying to install Windows 10 onto my folk’s museum piece Inspiron. This has provided further excitement and some additional chaos so if I do not reply promptly you will understand why. :mad:

Thanks, again. :)

Plastic washer is no use for to act as a seal on a cistern. I think that is your problem.
Rubber washer much better and the rubber washer type with a raised lip, (as the Armitage washer is in your photo) is perfect for to centre the siphon in the hole of cistern.
 

Reply to Siphon continues to leak from lowlevel WC. in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

New Posts Threads Members

Top