Replacing a Toilet Syphon - Choosing the Correct size

[Skavenger]

Hi,

The Flush / Siphon in our cistern al has been playing up difficult to flush and has now got to the point where it’s becoming a real issue. It’s an old toilet and seems to have a one piece flush / Siphon. How do I ensure I get the correct size / type replacement.
Only markings on the top of the blue Syphon are the names “Caradon Bathrooms Ltd Made in England” and a clock face on its 96 and an arrow pointing to the 5 - is this Month/ Year of manufacture (May 96)?
Measured from the bottom of the flush to the underside of the cap of the Siphon (as per pictures) is 237mm. The outlet pipe into the toilet bowl has an external circumference of about 12cm.
I take it I empty the cistern, tie off the inlet (to stop water re filling, then undo the plastic nut on the underside of the cistern, disconnect the handle and replace?

Just need help getting the correct replacement. Screwfix or City Plumbing link would be best.

 

[HERTS P&D]

Buy this one:

https://www.screwfix.com/p/thomas-dudley-ltd-adjustable-siphon-237mm/9756F?gclsrc=aw.ds&gad_source=1&gclid=CjwKCAiA65m7BhAwEiwAAgu4JFmACL9oXCeCGeYQFMDl_aJks9CEhPRBS0l12-0ZTbCBzGpuVggUmBoCZSgQAvD_BwE&gclsrc=aw.ds

Andy

 

[HERTS P&D]

Don't tie up the inlet, isolate the water or drain dowmn.

Andy

 

[Skavenger]

I looked at that one thanks.

 

[Johntheo5]

You don't need to replace it, when you remove it, you can just cut a bit of plastic to replace the bit inside the syphon, you can see quite easily how to take it apart, the bit of plastic doesn't require to be a tight fit, it just pushes some water down the outlet to start the syphon effect when you piull the handle.

 

[ChrisJP]

It's true you don't really need to replace the whole syphon and you can fix it by just replacing the diaphragm.
However, a lot of replacement syphons are now two-piece, so the main syphon unit can be separated from the flush tube bit that exits the cistern. That means in future you won't need to drain the cistern and remove the whole syphon when you need to replace the diaphragm.

 

[Johntheo5]

No more pumping of the handle up and down, you will be flushed with success.

 

[Fredstudio]

Hi,

The Flush / Siphon in our cistern al has been playing up difficult to flush and has now got to the point where it’s becoming a real issue. It’s an old toilet and seems to have a one piece flush / Siphon. How do I ensure I get the correct size / type replacement.
Only markings on the top of the blue Syphon are the names “Caradon Bathrooms Ltd Made in England” and a clock face on its 96 and an arrow pointing to the 5 - is this Month/ Year of manufacture (May 96)?
Measured from the bottom of the flush to the underside of the cap of the Siphon (as per pictures) is 237mm. The outlet pipe into the toilet bowl has an external circumference of about 12cm.
I take it I empty the cistern, tie off the inlet (to stop water re filling, then undo the plastic nut on the underside of the cistern, disconnect the handle and replace?

Just need help getting the correct replacement. Screwfix or City Plumbing link would be best.

View attachment 366772View attachment 366773View attachment 366774View attachment 366775View attachment 366776

Sorry to ask another question in a post. But the measurement given here is also the overflow measurement of the syphon. Were older syphons all internal overflow even though toilets were fitted with an external overflow

 

[Johntheo5]

Mine is ~ 35 years old and hasn't a external overflow and neither had the original 55 year old one. This 35 year old one doesn't have a adjustable flush like the one shown above which has a blue plug near the bottom, its set to give a small flush, you can see the syphon breaker hole above it, you just move the plug up which will then cover this hole and uncover the lower hole to give the maximun flush, not quite as convenient as the two button flush though!.

 

[Johntheo5]

Deleted, double post.

 

[Fredstudio]

The internal overflow flow works by the water level being above the internal spill over level of the syphon. How do the order ones not have the same action happing on theirs. Thanks

 

[JimCrow]

Sorry to ask another question in a post. But the measurement given here is also the overflow measurement of the syphon. Were older syphons all internal overflow even though toilets were fitted with an external overflow

Most water boards back then required a warning pipe from a cistern to minimise water wastage due to a failed ballcock also older cisterns had a 2 gallon flush so the top of the syphon sat higher in the cistern above the fixing holes/cut outs hence they had external overflows.

 

[Skavenger]

Buy this one:

https://www.screwfix.com/p/thomas-dudley-ltd-adjustable-siphon-237mm/9756F?gclsrc=aw.ds&gad_source=1&gclid=CjwKCAiA65m7BhAwEiwAAgu4JFmACL9oXCeCGeYQFMDl_aJks9CEhPRBS0l12-0ZTbCBzGpuVggUmBoCZSgQAvD_BwE&gclsrc=aw.ds

Andy

So I bought this Dudley Turbo 88 Duo Flush Suphon and fitted it yesterday.

It all went in ok, but I now have a leak from the underside of the cistern. I did not use any PTFE or sealant (it says sealant is not required)

Couple of questions to hopefully resolve this:

1. On the underside of the syphon, where it goes through the bottom of the cistern, there is a large black sealing washer (as shown on these installation instructions here). It is serrated on one side, however the instructions do not say which way around it goes? Does the serrated side face up towards the syphon or down towards the cistern.

2. Should I use some sealant between the sealing washer and bottom of the cistern? If so what would you recommend (Screwfix link would be great).

3. Should I use some ptfe tape on all the plastic threads?

4. The bottom of the new syphon is relatively the same as the old, but not as high, should I lift the new syphon to match the hieght of the old one? (Seems to work fine as is though?)

5. My toilet has a pipe from the underside of the cistern to the bowl (old fittings shown before swapping), I assume the cone washer sits with the flat side on top?

When dismantling, I found that only one screw had ever been used to hold the cistern to the wall and that its had completely rusted away, so the only think holding the cistern up is the pipe work!! I'd like to take it off and fit properly, but the isolator tap is about 900 years old and jammed with age and paint!!

 

[Skavenger]

Well I refitted everything, this time with the aerated edge of the sealing washer face down. Even managed to get the stop cock to work and removed the cistern to fix the attachments. Plenty of PTFE on all the threaded parts and the damm thing is still weeping water from the underside where the syphon exits the cistern. I am going to try some silicone sealant on the inside and see if that sorts it?

 

[Johntheo5]

I just put plenty of cheap clear sealant around the syphon where it exits the cistern on the outside and just tighten the nut, Ive never put sealent on the inside.
washer serrations downwards is correct.