Concealed Cistern - Intermittent siphon problems

[GeoffG]

I have a concealed cistern in a 20 year-old house. It is the old syphon type, and over the last couple of months it has started to have an intermittent problem.

It seems like the siphon washer/diaphragm is failing, and sometimes it's hard to get the siphon to start, and it takes repeated attempts to get it to flush.

BUT, other times, it can go a whole day or more with no problem at all, flushing absolutely fine. I find that hard to understand.

There is an access panel above so I can get to the top of the cistern, but there is no access to underneath the cistern, and it would be a BIG job to get to it - removing a large metre-high mdf panel held by 10 screws that have been countersunk, filled flush to the woodwork and painted over. (Not by me!)

Is it possible that there is debris or some temporary problem that will go away, or do I have to resign myself to taking the woodwork apart and repairing or replacing the syphon?

(BTW I am in two minds about getting a new dual-flush cistern, if it is necessary, rather than repair the old, because of this:
The water-saving device wasting billions of litres every week - https://www.bbc.co.uk/news/uk-54326178 )

 

[steadyon]

1. Needing repeated attempts to flush in a WC with a syphon, rather than a drop / flush valve, is generally a sign that the diaphragm washer in the syphon has gone hard / torn. The diaphragm is supported by a sort of mesh, which could account for it sometimes working, if the pieces of the diaphragm line up.
2. Replacing the diaphragm washer requires the cistern to be disconnected from the bowl. With a close-coupled toilet (cistern is attached directly to the bowl) this is a fairly major job. With a low level but not close coupled toilet (cistern just above bowl level and connected by a flush pipe) it is generally not so much of an issue.
3. There is an exception to 2. above. If you have a cistern with a Dudley Turbo 88 syphon fitted, you can replace the syphon diaphragm without removing the cistern from the WC.
4. In summary, if you are lucky you will have Dudley 88 and the job may be fairly straightforward. If you aren't lucky, you will have to dismantle sufficient of the surround to gain access.
5. You can get dual flush syphons now. Whether it would fit your set up - probably, but check first. Would definitely need full access to cistern.

 

[GeoffG]

1. Needing repeated attempts to flush in a WC with a syphon, rather than a drop / flush valve, is generally a sign that the diaphragm washer in the syphon has gone hard / torn. The diaphragm is supported by a sort of mesh, which could account for it sometimes working, if the pieces of the diaphragm line up.
2. Replacing the diaphragm washer requires the cistern to be disconnected from the bowl. With a close-coupled toilet (cistern is attached directly to the bowl) this is a fairly major job. With a low level but not close coupled toilet (cistern just above bowl level and connected by a flush pipe) it is generally not so much of an issue.
3. There is an exception to 2. above. If you have a cistern with a Dudley Turbo 88 syphon fitted, you can replace the syphon diaphragm without removing the cistern from the WC.
4. In summary, if you are lucky you will have Dudley 88 and the job may be fairly straightforward. If you aren't lucky, you will have to dismantle sufficient of the surround to gain access.
5. You can get dual flush syphons now. Whether it would fit your set up - probably, but check first. Would definitely need full access to cistern.

Thanks v much for your v helpful reply.
I fitted a Dudley 88 upstairs - but it's not that downstairs sadly. It's actually dual-flush version of the 88 I fitted upstairs too, although the hold-down-to-short-flush is not v ergonomic and doesn't get used.
The problem one is not close-coupled, but the nightmare will be getting access as described, to release the old siphon. If/when I do repair the siphon, (rather than replace the cistern) I will certain put in a new Dudley 88! Such a good design!!

 

[Ric2013]

(BTW I am in two minds about getting a new dual-flush cistern, if it is necessary, rather than repair the old, because of this:
The water-saving device wasting billions of litres every week - https://www.bbc.co.uk/news/uk-54326178 )

Do not try to reduce your water flush volume by fitting a drop valve or new cistern to your to your existing pan. It may not work properly - a pan designed to flush with 9l of water will not always work properly if you reduce the flush volume.

Drop valves tend to need regular maintenance otherwise they let by. Ideal Standard ones tend to last 4 years before needing a new outlet washer, while the old siphon diaphragms typically last 20 years or so. You may still save money in reduced water bills depending on how often you flush and how much you spend replacing the outlet diaphragm. That said, some drop valve designs over the years have been excellent (my father's Italian Pucci concealed cistern has been in daily use since 1972) and can go well over a decade without attention.

A dual flush siphon, however, will not waste water by letting by, but you may find you end up double flushing if the half flush proves insufficient. New siphons are nearly always dual flush, so you may be stuck with one unless you prefer to repair your existing siphon, but that is not a problem as they now tend to be pull and hold for half flush so accidental activation of the half flush feature is unlikely. In your case, a new siphon that can be serviced from above may prove a good option.