Concealed cistern - syphon vs valve?

[bertiewooster]

I'm hoping someone can help with the following. By the way, I'm not a plumber and intend getting a plumber to do this work.

I'm thinking of removing the existing close coupled loo from the downstairs cloakroom to be replaced by a back to wall pan and concealed cistern. However I'm just getting to understand that there's a choice of valve or syphon cisterns, and most stuff I've read says syphons never leak, but valves may/will in time. Given that the plan is for the cistern to be concealed, I'm concerned about possible leaks in the future and access to fix.

This is particularly relevant as two years ago I changed the loo in the ensuite to a concealed cistern within a cabinet which looks fantastic but only has access through a clip-on front panel. There is now an intermittent, really irregular minor leak from somewhere in this loo which appears on the left side of the loo and only started about a month ago. It doesn't happen on every flush and I've gone from thinking it must be a crack in the pan, to now believing it might have something to do with the pipework. Inspection of the cistern through the front panel shows it is completely bone dry.

Can anyone help with the leaking problem which will then help me to make a decision on the new work planned? Thanks

 

[Plouasne]

Both have good and bad points, a syphon type will eventually stop flushing, a valve type will after a time let by, both faults means that somebody has to get access to the mechanisms, with a syphon type an overflow has to be provided, a valve type overflows into the pan

Take your pick

Try using kitchen paper to find the leak, it could be splash over when the pan is flushed, could be a leak between pan and flush pipe, it could be a slight flaw in the china where the pieces are assembled together to make the w/c pan

 

[bertiewooster]

Thanks for your quick reply. I've already tried using loo paper to track the leak, but this has proved inconclusive. By the way, I've already approached the supplier of the loo, who have a lifetime guarantee on their sanitaryware, to be told that they don't believe a crack/flaw would appear so long after installation. They have "offered" to let me buy a new loo, have it installed, send back the old one, and they will then inspect it. However they will only give me a refund if they determine there is a crack. I haven't yet decided how to reply.

 

[Phil]

Poulsane,

Don't all syphons have an internal overflow already?

[DLMURL]http://www.opella.co.uk/PDF%20Lefleats/Syphonoverflow.pdf[/DLMURL]

 

[Plouasne]

Phil,

I will be the first to admit that I am not up to-date with the regs seeing that I left that country 20 years ago, when I was in the game over there what you have posted in the link was illegal, the crown of the syphon had to be above the overflow level

 

[Phil]

Hey Poulsane, you know more than me, my post was more of a question than a statement.

 

[MarkB]

It used to be that case that WCs were not allowed to overflow directly into the pan, whether it was a flush valve or a syphon.

If you couldn't run the overflow pipe externally a tundish had to be installed. The Water Regs were changed some time ago and now it's ok to discharge the overflow into the pan. As far as I'm aware most replacement syphons now have internal overflows.

Mark

 

[Phil]

MarkB, what do you think the reason was for not allowing overflow water to go back into the pan?

Was is just as simple as an external overflow is easier to spot and caused enough nuisance that the float valve would be fixed straight away thus saving water?

 

[MarkB]

I'm hoping someone can help with the following. By the way, I'm not a plumber and intend getting a plumber to do this work.

I'm thinking of removing the existing close coupled loo from the downstairs cloakroom to be replaced by a back to wall pan and concealed cistern. However I'm just getting to understand that there's a choice of valve or syphon cisterns, and most stuff I've read says syphons never leak, but valves may/will in time. Given that the plan is for the cistern to be concealed, I'm concerned about possible leaks in the future and access to fix...........

Bertie,

As mentioned by Plousane, both may need servicing in the future. Generally speaking the flush valves need new sealing washers and the syphons new diaphragms. If you opt for a syphon it may be worth considering a 2-part one (Dudley turbo 88 or similar) as you can access the diaphragm without having to remove the whole syphon from the cistern.

MarkB, what do you think the reason was for not allowing overflow water to go back into the pan?

Was is just as simple as an external overflow is easier to spot and caused enough nuisance that the float valve would be fixed straight away thus saving water?

Phil,

Yes - like any warning or overflow it was supposed to cause a nuisance. Some of the flush valves that I've seen letting by you can barely see, just a hint of a trickle down the back of the pan.

Mark

 

[david williams]

you can still get syphons without intergrated overflow,but you wonder while we are all being told not to waste water,that overflowing into pan is allowed as most people will just let it carry on,the overflow pipe was designed to cause a nuisance so that something was done about it and thus prevent waste

 

[Bernie2]

Perhaps in the future we may all be required to put one of those blue flush tablets in our cisterns. Then if they do overflow down the pan you can probably see it.

 

[MarkB]

Perhaps in the future we may all be required to put one of those blue flush tablets in our cisterns. Then if they do overflow down the pan you can probably see it.

The problem with that is that all of the flush valves I've come across state clearly "Do not add any cleaning chemicals directly into the cistern" . Something to do with damaging the washer and fragile flushvalve plastic maybe?

Mark

 

[Mushybees]

The overflow will dribble into the pan but when it fills to a certain level the syphon will start a flush. When it flushes itself in the dead of night it's more than enough of a nuisance

 

[Alanka]

I have just completed a refurb where a back-to-wall fully concealed wc was fitted. The standard tiny lidded slot in the counter-top over the the concealed cistern was clearly going to be inadequate for access if a leak developed under the cistern, and was scarcely big enough to allow a change of flush mechanism if that ever became necessary. A bit of a joke really!

So I provided a completely removable section in the worktop that gave good access to the cistern and connections. I used a cut-down worktop aluminium joining strip to conceal the cut in the worktop - which looks very neat. This has already been used to access the cistern to adjust flush volumes.

 

[stevetheplumber]

you can still get syphons without intergrated overflow,but you wonder while we are all being told not to waste water,that overflowing into pan is allowed as most people will just let it carry on,the overflow pipe was designed to cause a nuisance so that something was done about it and thus prevent waste

biggest waste of water is six litre cisten which need to be flushed at least twice to get rid of no 2s