This has to be one of the most amusing anecdotes on this forum. You with the hoover and starting off the siphon. Brilliant, and thank you!
This must be incredibly frustrating, however. I don't have specific knowledge of that model, but you do appear to understand the basic principle of how a siphon works so perhaps two heads are better than one.
I would agree the problem with spray is probably something to do with that rectangular piece (I don't know what what the rectangular piece made of and I can't tell whether it is merely a seal of sorts to prevent water squirting out or B. part of a mechanism to admit air if the chain isn't held down/is held down thus breaking the siphon early and so allowing a dual flush?). It has occurred to me that perhaps it was previously stuck and you've somehow freed it off and so it is now working correctly. Worth bearing in mind that if something has come loose, it may still be in the system - so be careful what you flush away.
I cannot understand why the flush fails to work, however. Even if some lifted water is being lost through the rectangular piece, the flush should still work initially as there should still be enough water pumped up to start the siphon. What I have noticed by looking at your picture is that the water level seems to have been set around an inch above that rectangular piece. This would appear to be wrong and if my suspicion of an early dual-flush mechanism is correct, may have been a way to save water to compensate for a stuck dual flush. It is amazing the lengths some people will go to to save water - perhaps because it is a very visible resource... unlike the embodied resources in food, energy, and consumer goods.
I would suggest the water level should ideally be an inch below the bottom of the invert, where the outlet pipe widens at the top of the waist on the outlet pipe (below the fulcrum). Perhaps this would also solve the squirting issue?
Have you tried filling the cistern to a higher level if only for experiental purposes and then attempting a flush? If it still discharges at a trickle, this would suggest there may be a blockage of some kind. Another interesting question is, if you block the overflow and force the cistern to 'overflow' internally via the flush pipe, does the pipe appear to be clear? If not in the siphon unit, perhaps something is obstructed in the downpipe (and I'm concerned it might be a siphon component).
The only other thing I can think of is that something is wrong where the flush pipe connects to your new pan or the waterways in the new pan are faulty or obstructed. If there is no way out at the bottom of the flush pipe, this would also explain the squirting at the top when you attempt a flush and create pressure.
Please let us know how you get on. I for one am interested in this headscratcher of a problem.
Thanks so much for your reply! In hindsight I should have added a couple of more details that at the time I didn't think were relevant - but actually were. I was obsessed by the hoover treatment and the old unit.
I have now resolved the issue but not without a few scrapes along the way.
The full story is that I approached my usual plumber to look at fitting the new bowl a few weeks before Christmas and he popped in and we talked through the process.
I had been to a reclamation yard - an excellent place/website not to far from Tunbridge Wells - and picked up a toilet bowl from about 1950 for £50 which had dimensions that were close to our broken one. And looks great.
My plumber explained that it would need a plinth to get the inlet pipe in the right alignment and, on inspecting the set-up - uneven lead downpipe etc he said that he would use Geocell to waterproof the joint rather than a flushcone.
It was all set for him to come round but then he contacted me to say that he had to stay at home with his daughter who had to stay at home due to Covid at her school and that he couldn't make it before Christmas.
So I decided to have a go. I am pretty handy and have helped dig out cement from a waste pipe once before and frequently change our ballcock valves and do other miscellaneous (compression only) plumbing. And I had made the plinth.
It was probably as well that my plumber didn't come round in one sense because immediately it became apparent that a floor board needed replacing (I'd done a couple before but this was under a key weight bearing point) - it had looked OK by my standard but it was one where the finger went straight through when tested!
I also spent time as initially mentioned replacing a split pin that the siphon arm was attached too that was on the point of shearing through - so that took a while to drill out the old encrusted one and replace.
But, and you may have guessed from the mention of Geocell, I overdid the stuff. I was so obsessed with not having a leak that by the time I put the thing together - getting the downpipe in place and cementing the waste pipe I thought that I had done a fine job and almost had a ceremonial cutting of the ribbon - well I invited my wife to pull the chain first - Hmmm - dribble, dribble and the problem that I first discussed.
I was panicking and thinking that the top end was doing the damage, and hence this forum post....and by luck, among searches I found a You Tube video of the very Japkap flush system. And I put a comment onto that video - and mentioned how great to see a video and that I had a problem, and after a bit of back and forth the most helpful Youtuber was definite that I had blocked the downpipe with Geocell.
I then had the issue of how to take it apart again - not wanting to disturb the cement - which I think I would have destroyed the toilet if I had tackled that.
Anyway, the solution was to take out the downpipe - which looked like it had been in place for over 100 years - to allow access to the back of the toilet inlet and clean it all out and to start again.
And to order a flush cone. Which I did.
So now, after taking the top cistern apart for my fourth time (yes four!) and digging out plaster behind the pipe to allow movement, I was successful in removing the pipe and seeing the ridiculous plug of Geocell that I had so zealously squeezed in on assembly.
I have now reconnected it all and, after twisting a bit of wire around the flush cone to avoid a slight leak all was almost good. Accept that the flush chain arm was not returning up after flushing - so I had to take the split pin out and remove a couple of washers that I thought would be good to keep the movement more controlled - wrong it needed play in the mechanism because it as all slipped to one side over the years.
I have now done that and, phew, it all works great!
What was probably going to take my plumber (estimate) half a day has probably taken me......well from before Xmas to yesterday to fix! I am in the final process of revarnishing the lovely old wooden seat and making good the pipe paintwork and flooring and will then take a video of the final job.
I am sorry that I didn't get back to this site to say that I had a fix, so sorry for wasting your time - but the hoover incident was just hilarious and horrendous in equal amounts!
(If you want to see related videos/pictures/correspondence go onto youtube and search "wooden japkap".
Thanks again, Happy New Year and Happy Plumbing!
