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Discuss I need help with an ancient Japkap model in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

Messages
3
I have a high level cistern and was replacing the toilet pan (waste ceramic completely cracked through) and was hoovering around before connecting the waste and the lead inlet pipe and was just absent-mindely gently sucking lead filings out of the inlet pipe - and whoops, the downpipe grabbed the hoover end and started a flush (my hoover had overcome the siphon.***.a terrible experience which was funny at the time - and very wet - a surreal experience of seeing water shoot out horizontally for about two feet). Having successfully rectified the mess and connected the new toilet I now find that I cannot flush it - the old Japkap unit appears to have not liked the hoover treatment - or the inaction over the last two months.*** water comes flying out (pic 1) where my yellow arrows point and the small rectangular piece flies up the plunger arm (is it meant to be loose?)
You can see in the second picture that this has a flap valve which appears to be in fine shape and moving very freely. (opening and shutting - no rust in the mechanism after so many years)
So there is not a successful flush and the water trickles down into the toilet and stops when it reaches the level of the arrows. There is no blockage in the upper U - that is clean.
Although the unit is rusty, I have replaced the split pin holding the plunger arm so that now rides smoothly, but still water comes out of the gap with such force that it sprays out between the cistern and the porcelain cover.
Has anyone experience of such an old unit and can explain how the design is meant to work? Or why it isn't? What am I missing?
Appreciate any help and thanks for reading!
John

Japkap3.jpgJapkap4.jpg
 

Ric2013

Plumber
Messages
2,466
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.
 
Messages
3
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!
 

Ric2013

Plumber
Messages
2,466
Actually I've watched your video and found it interesting. Can see this has been rather a 'mission', but it must be very satisfying to get to the bottom of it and I can see why you are keen to keep that toilet. It may be old, but it's in good condition and hasn't been messed about with, so it certainly adds character to the house. Congratulations on your patience with that lead pipe, by the way.

Regarding my previous comment about the water level, having seen your installation I take back what I said in that I can see that, if the water level were any higher, your floatvalve (ballcock) would be sitting in water and presenting a possible back-siphonage risk.

Hopefully I'll remember to look up the links to find the finished result when you post them...
 
Messages
3
I have the same Japkap cistern and only get a half flush water empties out only to the level of the arrows in the picture from John George post 21Dec.
Is it something to do with the copper (I Think) rectangle part the flush rod goes through being loose?
All other parts are in good shape.
Any advice.
 
Messages
3
I have the same Japkap cistern and only get a half flush water empties out only to the level of the arrows in the picture from John George post 21Dec.
Is it something to do with the copper (I Think) rectangle part the flush rod goes through being loose?
All other parts are in good shape.
Any advice.
From what I have learnt, that rectangle is designed to be loose. If it wasn't, the flush rod would just bind up as it moves through it. Is your flush slow? (sorry - sounds a bit personal) My experience was that I had managed to pretty well block the down pipe so the flush was slow and the siphon effect wasn't working properly and so the flush took the first opportunity to stop - when air was allowed in through the top of the 'dome'.
If the water is wooshing out it doesn't have time to stop at that point and the whole tank empties.
So, and I am not a plumber, I am just someone who battled with one of these for a few weeks (!) I would guess that there is a constriction somewhere between the cistern and the water appearing in the pan. (or maybe something has got into the 'dome' and is causing an issue.
Anyway, I had help on YouTube, and if you go onto YouTube and search 'Japkap wooden' and look at the WW2 reference you could join the conversations! Cast Iron Cisterns 486 was extremely helpful to me.
Also that video might just help! And his answers to me might also shed more light on your issues.
Good luck!
John
 
Messages
3
From what I have learnt, that rectangle is designed to be loose. If it wasn't, the flush rod would just bind up as it moves through it. Is your flush slow? (sorry - sounds a bit personal) My experience was that I had managed to pretty well block the down pipe so the flush was slow and the siphon effect wasn't working properly and so the flush took the first opportunity to stop - when air was allowed in through the top of the 'dome'.
If the water is wooshing out it doesn't have time to stop at that point and the whole tank empties.
So, and I am not a plumber, I am just someone who battled with one of these for a few weeks (!) I would guess that there is a constriction somewhere between the cistern and the water appearing in the pan. (or maybe something has got into the 'dome' and is causing an issue.
Anyway, I had help on YouTube, and if you go onto YouTube and search 'Japkap wooden' and look at the WW2 reference you could join the conversations! Cast Iron Cisterns 486 was extremely helpful to me.
Also that video might just help! And his answers to me might also shed more light on your issues.
Good luck!
John
Hi. Thanks for your response. I have followed your youtube and replied to the conversation hopefully cast iron can see what's wrong. Here's a link to my vid
 

Ric2013

Plumber
Messages
2,466
Hi. Thanks for your response. I have followed your youtube and replied to the conversation hopefully cast iron can see what's wrong. Here's a link to my vid
Flush does seem a tad slow, but you don't have 6' of flush pipe to increase the draw on the siphon, if testing that way.

Try it with a flush pipe attached and I suspect the flush will be much faster and the small amount of air ingress around the plunger won't matter.
 
Messages
3
Flush does seem a tad slow, but you don't have 6' of flush pipe to increase the draw on the siphon, if testing that way.

Try it with a flush pipe attached and I suspect the flush will be much faster and the small amount of air ingress around the plunger won't matter.
Solved!
I put a split pin on plunger rod above copper rectangular piece and a piece of self adhesive rubber piece on the underside. This made the rectangular copper cover return and prevented air getting in which enabled a full flush!
However when plumbed into toilet I noticed another problem, which may have been the problem all along. The brass pull handle. Whilst only 115g it was heavy enough to prevent the cast iron flush arm from rising back to its position which resulted in half flush only.
The Japkap a finely balanced piece of engineering!
 

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