Low Level Cistern - Connect Overflow to Flush Pipe

Hi all
As the subject really. Is there any reason why I shouldn't pipe an overflow from the side of a cistern down and under said cistern and tee into flush pipe? If so, is there a reducing tee type fitting that would take 22mm overflow pipe into the side of 38mm flush pipe? The current overflow goes into a room soon to be a kitchen (hopefully). I want to keep the existing cistern, box it in and fit a back to wall pan. This way I have one toilet in the house that gives a decent flush volume (unlike the flush three times 6Litre models currently on the market).
TIA
Phil
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On Tue, 6 Mar 2007 14:47:00 -0000, "TheScullster"

So long as the flush pipe doesn't get blocked furth of the overflow connection and the cistern doesn't overflow at the same time ...bit unlikely I admit ...suppose it's the same with syphons with builtin overflow arrangements ....did you consider changing to one of them ?
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Call me a cowboy - but here goes .................. When I fitted my cloakroom out a few years ago, the only option I had for the overflow was to run it about 8 metres through my lounge. I ended up drilling a hole in the top of the soil pipe and feeding the overflow, incorporating a u-bend directly into this and sealing with silicone - topping up the u-bend with water to create an air lock. Afterwards I thought that the water in the u-bend would soon dry up and I would forever be smelling the contents of the drain through the cistern but we've never smelt anything and I've only topped the trap up once !
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On Tue, 06 Mar 2007 15:57:34 +0000, Franko wrote:

Maybe you've got an overflow that's keeping it topped up and because you haven't fitted a tundish you can't see it!

yeee - haaah!
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On Tue, 06 Mar 2007 14:47:00 +0000, TheScullster wrote:

You can do it and IIRC BES have bits for doing so but it looks sh1t3 (unless it's all concealed). There are various alternative flush valves with internal overflow you could use. If you have a standard size syphon valve you can get 8" ones which are usually low enough to overflow internally, or there are flap valves (which can use a regular-looking handle) or push-button valves (many dual-flush) from Multiquick and Opella.
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Yes, it's much, much better to fit a new siphon with built in overflow. You can go to the flush pipe but it should be via a tundish (where the pipe ends, there's a gap and then more pipe with a flared top to catch the flow - this gives the required air break) and it looks (as he says) sh1t. You can get interna;l overflow siphons from B&Q (I think).
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Bob Mannix
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As I udnerstand it, and I could be wrong, there's no requirement for a visible tundish as one would be able to see the overflow flowing into the pan. That's why the european style flappers are now allowed.
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It *may* be the case that the regs have changed and the tundish is not required (don't know) but it wasn't so you could see an overflow, it was to provide an air break between the pan and the cistern.
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On Tue, 6 Mar 2007 14:47:00 -0000 someone who may be "TheScullster"

Provided it is allowed in your area.

There certainly used to be. It clamped onto the flush pipe with some bolts and had a side connection for the overflow.
Alternatively, as has already been suggested, replace the siphon with one with an internal overflow.
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David Hansen, Edinburgh
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"David Hansen" wrote

The syphons I've seen with internal overflow provision, do so with a very small hole. These look like they would only accomodate a slight weep of the float valve - anything worse hitting the floor! Are there syphons out there that can cope with overflow from a serious valve failure? The feed to my cistern is low pressure.
Thanks
Phil
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The very small hole is to allow air to escape so the siphon fills (otherwise it wouldn't). Once full it flushes the toilet, the small hole not being enough to break the siphon. This empties the cistern as per normal and the cycle repeats. It should thus be able to deal with at least a cictern filling permanently at its normal full rate.
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wrote:

Unless the waste pipe blocks at the same time in which case you are in the S*** ....That was the advantage of seperate overflows to outside ...Unlikely I agree tho'
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On Wed, 07 Mar 2007 11:00:15 +0000 someone who may be Stuart B

However, a dripping warning pipe in winter can slowly freeze solid, with predictable results, so it is a matter of swings and roundabouts.
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David Hansen, Edinburgh
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On Wed, 07 Mar 2007 12:35:36 +0000, David Hansen

Freezing winters ..Nah..That was years ago .haven't you heard of global warming ..lol?
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