Flush mechanism on a syphonic toilet

7 Feb 2012
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United Kingdom

Close coupled old syphonic toilet. Is there anything special about the flush mechanism on a syphonic toilet or is it just a standard flush and the syphonic part takes place in the pan ?

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Thanks for that. It does answer my question which, on reflection, I didn't really word very well.
I meant to ask "is there anything special about the flush mechanism in the cistern." So it is looking like there isn't.


Pictures are better than words, the siphonic toilet be design is down to the siphonic action of the pan, rather than the mechanics of flushing mechanism in the cistern!
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If it's close coupled you have to be very careful not to break the vortex tube.you have to be equally as careful when reassembling them too.
Wrongly reassembled your toilet will not flush.
Thanks all.
This is for a remote tenant of mine. I will be going over today. I was told that something was broken in the cistern and it would not flush, and that the handle was loose.
I was just concerned that there was something different with the flush mechanism on a syphonic.
I expect this to be straightforward, C-link or similar.

There is what as known as a bomb that fits into the syphon from underneath on syphonic wc's.It won't work well without it or broken.
google syphonic bomb/aerex etc.
Mmmm interesting.
The immediate problem is that it is broken and does not flush at all but when it was working it was odd in behaviour like this .... //www.diynot.com/forums/viewtopic.php?t=173858 i.e. Fills up a long way and flushes badly.
I will get the make and a photo when I am there and see if I can source a 'bomb' and the close couple seal.


Just thinking about this some more. I remember maybe 12 or 15 years ago we had a plumber visit this toilet because the cistern was leaking. The ceramic was cracked around the overflow pipe so it needed a new cistern. The plumber managed to get one to match but it seems possible to me, now, that this may not be the correct cistern for the pan and the bomb.
That's if there is even a bomb in there !

If there's no bomb then the pan would not work as intended, period. The pan relies on the bomb, (the proper term is Aspirator), to create a slight vacuum in the middle trap of the pan when a flush commences, and set off the syphonic action to clear the contents of the pan. The flush alone does not have sufficient force to clear the pan as it would with the normal 'wash down' type pan.

Suspect the bomb isn't working at present, could be as simple as a perished washer not making an air tight seal. Will need to dismantle and check, replace bomb/washers as required. It is vital to reassemble ensuring air tightness, or as now, the toilet simply will not work as it should and block!

The immediate problem was fixed, handle and metal link had come undone.
The bowl is an Armitage Shanks and is marked on the outside Unisyla so I'll try and source an air extractor / bomb and resolve the poor flushing.

Got to do this job today. Yes, there was a bomb/aspirator already fitted but as suggested the washer was perished and a very loose fit on the pipe.
I fitted an Armitage aspirator, installed the new washer low down on the pipe and then lowered the cistern very slowly into place so that the new washer would find it's correct position, then did up the close coupling bolts with new doughnut installed.
When flushed now, the toilet bowl water level just rises slightly then all sucks out whereas before the water level in the bowl just rose up slowly and then sank away slowly, so all in all looking good.

Thanks all.


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