Induced siphonage in soil stack

Hello all,
I have a soil stack to which is connected the waste from the bath and basin. Directly above this, about 8", is the waste from the toilet. At the top of the soil stack is fitted an air admittance value.
The bath has a shallow bath trap fitted and the basin a standard bottle trap. The problem is that when the toilet is flushed a few times the water in the bath trap is sucked out. This leaves a very unplesant smell in the bathroom.
I was thinking of fitting the waste from the basin and bath lower down the soil stack to overcome the problem of siphonage. Will this work?
Obvioulsy I only want to try this once as it means cutting out holes in the soil stack.
Many thanks.
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If you have enough room under the bath replace the bath trap with a waterless HepvO valve.
Get a 40mm HepvO valve and knuckle converter. Cost about 13. Remove the bath trap and replace with the other items.
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On 2 Oct 2003 11:53:32 -0700, Lazy Beetle wrote:

Gosh, was that valve expensive? B-)
Have you checked the air admitance valve works and easyly lets air in.
As for the relative positioning of the bath/basin pipe and the toilet I thought there were regulations that said the bath/basin stuff should be above the toilet or below by at least X. Don't know what X is but > than 8".
--
Cheers snipped-for-privacy@howhill.com
Dave. pam is missing e-mail
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On Thu, 02 Oct 2003 21:04:09 +0100 (BST), a particular chimpanzee
and produced:

Connections on opposite sides of the stack within 200mm of each other should be avoided, but there is no restriction for connections on the same side. This is to avoid crossflow, not siphonage.
I agree with you; check the air-admittance valve.
--
Hugo Nebula
"You know, I'd rather see this on TV,
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On Thu, 02 Oct 2003 21:04:09 +0100 (BST), "Dave Liquorice"
I once saw a flat where the air admittance valve worked perfectly -- Until you put the lid back on, over the boxed-in cupboard where it had been installed ! Placing the valve in a small sealed space isn't the best idea.
-- Smert' spamionam
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