WC overflow going into a sink waste-pipe, soil pipe or shower cubicle?

As I understand it, an overflow has to bring attention to itself, so if plumbed into a drain or other hiden recepticle , has to go via a 'tun dish' so that the abnormal water flow is apparent and the fault can be rectified.

AWEM

On Fri, 18 May 2007 17:09:16 +0100, James B mused:

The idea of the overflow is not just to discharge the excess water but to also warn you of a problem. If it's discharged directly into a waste pipe you won't know that it is overflowing, unless you fit a tundish. You can get sealed clear ones that fit inline in the overflow pipe.

On Fri, 18 May 2007 17:09:16 +0100 someone who may be James B wrote this:-

Warning pipes should warn that there is an abnormal condition, so they are harder to ignore. The answer to your question is, in general, no.

Your guess is wrong.

On Fri, 18 May 2007 17:24:34 +0100, David Hansen mused:

You sure? AFAIAA you're not allowed to discharge anything onto a public area, fans, flues, wastes etc...

Thanks - that sounds like an excellent solution. Can anyone provide a link to a reasonably-priced one? I was thinking of installing a fresh new WC unit, or even just a new cistern, so if anyone knows of one with the integral overflow system already built in, I'd be grateful to know where I can get one - especially from a DIY chain such as Wikes, B&Q or Focus.

Thank you,

Jim

Hoping someone will clarify, as my C/H boiler flue comes out above a public pavement...

Jim

Thanks to the replies concerning the 'tundish'. That would certainly be an option. I'm curious about the WC syphons with integral overflow. They sound ideal - from a visual point of view at least.

Jim

Virtually all new WCs have an integral overflow - the regs changed a few years ago, and now most have changed over.

Thanks for bringing me up to date! It's nice to know I can therefore probably nip out and buy a new cistern containing one from a local B&Q or suchlike.

James

I found out about this at school about 2 years ago, but one point I can't understand is that if a loo cistern starts to vent water because of a faulty ball valve, how does the loo cope with all this water if it happens to have a blocked waste/soil pipe?

When the plumbers, at school, did all the work of removing dead leg pipes and removing all the tanks in the system for legionella problems, they had to change several ball valves in the toilet systems, so they could cope with mains pressure. I would think that a full bore fault on a ball valve will result in quite a bit of flood damage in a house situation, if the waste pipe was blocked.

Dave

On Fri, 18 May 2007 22:16:12 +0100, Dave mused:

It's unlikely that that will happen though, one or the other maybe, but both together, slim to no chance realistically. There's a linit on how far you can go with it all.

In article , Dave writes

That's two faults and unless it's a real safety critical system then system designers and legislators generally rely on the single fault principle ie. no single technical failure, erroneous action or mistake should lead to damage, fatalities or serious injuries.

I think there's a general rule that the single fault should be noticeable so that it's your own fault if you ignore it and allow a subsequent fault to cause damage, injury etc.

A full-flow fault on the cistern valve can result in overflow into the room without actual blockage of the overflow pipe, especially if it has a long run without a good fall (I've seen overflows with uphill flows!). A cistern with internal overflow generally deals with this situation OK but isn't as good at showing a slowly dripping cistern valve: you just get a trickle down the back of the pan which is hard to detect.

You can often convert a normal cistern to internal overflow by fitting a suitable flush valve. If the existing flush valve is quite tall you can get shorter (8" IIRC) ones which will overflow internally before the water reaces the rim or holes in the cistern. Otherwise you can get flap valves or push-button valves.