OK to lower my toilet cistern?

[Lobster]

I have a concealed loo cistern behind a panel, which has developed a leak at the exit, which is clearly the result of the exit pipe being shoved up against the AAV on top of the soil stack, and the joint being severely strained. So I want to reposition the cistern a bit. Ideally, it would go forward and a bit lower than before, in order to be able to gain access to the cistern from above (it's completely blocked by a large purlin at the mo. Don't ask - he wasn't a great plumber.)

Question - at the moment the bottom of the cistern is about 30 cm above the rim of the bowl, which is fed by an L-shaped pipe 1.75"?) from the cistern. If I lower the cistern so that the drop is only, say 10cm above the bown, would this mess up the flush? I can't decide logically whether the answer is "yes of course", or "no the length of the drop is irrelevant".!

Thanks all David

[A.Lee]

No. 2, - irrelevant, within reason. The L shaped pipes come in a size of around 60cm x 30cm, and are supplied to be cut to size. Alignment is key to a good fit - as you know. I've found it is the cistern joint that leaks before any other - the rubber connector to the pan seems a lot better than the little rubber o ring on the cistern joint. Alan.

[Roger Mills]

Bearing in mind that close-coupled cisterns sit directly on top of the bowl, I would think it would be ok - even though the water from close-coupled cisterns has a more direct path than yours.

[Roger]

The message from Lobster contains these words:

It probably makes some difference but probably not enough to matter. The higher the cistern the more potential energy the water starts off with but set against that the longer the pipe the more resistance to flow. I must admit it is a long time since I have seen one but I don't think the old high level cisterns that used to be commonplace were conspicuously better flushers and close coupled cisterns of course sit right on the bowl and mostly work ok with less water per flush than was the norm.

[Stuart Noble]

I changed the height and the horizontal distance on mine recently, both by about 75mm, and it all works fine.

[sm_jamieson]

Ya reckon ? The outside loo I removed when demolishing, could have flushed a cat down, such was the ferocity (and noise) of the flush. I should imagine the cat would add to the noise also. Of course the enormous amount of water helped too. The water head was around 1.5 metres. Simon.

[Lobster]

Thanks all, I'll get me hacksaw out then. And if the lowering does have an adverse effect, I'll just have to feed more all-bran to SWMBO.

David

[don't worry, she doesn't 'do' usenet]