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Hugo Nebula Hugo Nebula is offline
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Default Drainage, drainage and drainage

On Fri, 31 Aug 2007 12:36:25 -0000, a particular chimpanzee,
" randomly hit the keyboard and produced:

1. For the upstairs bathroom, I'd need to have a horizontal soil
branch pipe 4m long (well actually the prescribed 18mm/metre slope)
from the loo, followed by 4m vertical drop, followed by a 1.5m
horizontal section up to the existing point were the soil pipe goes
underground. (no offsets necessary in horizontal pipework).

2. Waste water from the kitchen is a bit of a problem as the kitchen
needs to be at the back of the building.

a) One solution is a 5.5m horizontal pipe run up to the same point the
upstairs bathroom goes underground - that concerns me as a long
horizontal kitchen sink sounds likely to clog.

b) Another solution is drop the upstairs bathroom soil stack closer to
the kitchen, resulting in a short upstairs branch pipe, 4m vertical
section, and a 5.5m horizontal section (of 100mm pipe) before it goes
underground.


So - my question is - does solution 2a or 2b sound better?


2a sounds better. If your soil stack is internal, you want to make as
least likely to block as possible. The kitchen sink branch would
probably be easier to clear. Your kitchen sink waste will need an air
admittance valve/trap over 4m.

3. A simple one this time. It would be convenient to repair that open
vent pipe to one of the rainwater branches - and for the internal
stack just to have an air admittance valve within the bathroom (above
spillover levels). I can't be sure if that complies with Part H -
though I don't see why not - whadyathink?


Rainwater pipes should NOT be used to ventilate a drainage system,
unless they meet the criteria for an open stack (900mm above or 3m
horizontally from any opening into a building).

Durgo say that their valve can be used without an open stack on a
system serving up to 5 stacks. The old rule of thumb used to be that
there needed to be an open stack at the head of any drain where Durgos
were used, and the AD does say, "where there is no open ventilation on
a drainage system or through connected drains, alternative
arrangements to relieve positive pressures should be considered". Your
rainwater gullies should be trapped, so these don't count.

5. HepVO - reading their docs seems to suggest use them and no AAV's
necessary - correct?


Well, they are a form of air admittance valve (they let air into the
pipe but not out), so they are subject to the same rules as AAVs.

I'm also thinking that a HepVO may better protect the kitchen against
backups in pipework?


OTOH, poo coming up into the kitchen sink is a good indicator that you
need to get your rods out, NOW!
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have you strayed?"