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Old August 31st 07, 02:36 PM posted to uk.d-i-y
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Default Drainage, drainage and drainage

I've read Part H back and forth, and I'm still not sure.

I'm converting an old chapel. It's got combined foul & rainwater
drainage. Pre-existing is a 1.1m deep manhole, 2m in front of the
building, followed by a 5m run to connect to the public sewer

Also pre-existing is 4 pipes come into the manhole, 1 pipe each for
rainwater from each side of the building (at half the depth of the
manhole), and 2 pipes originally connected to ground floor toilets at
or near the front of the building (1 is still connected to a toilet,
one to a sink) right at the bottom of the manhole. All are working
correctly.

The only soil vent pipe was a branch off one of rainwater pipes,
unfortunately part of this pipe has collapsed.

Now, ideally, I'd like to route the soil stack internally up to these
existing ground floor toilet connections.

My questions:

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).

Is that layout likely to be acceptable to BC and likely to be trouble
free?

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.

In this solution the kitchen would connect close to the bottom of the
4m section. I think the advantage would be the ground floor horizontal
section would clear better because of upstairs loo flushing.

The disadvantage would be if the stack blocked at this ground floor
bend and backed up - it's close to the kitchen branch - yuck. There's
a Part H rule about no connections within 750mm of a stack offset - I
guess for exactly that reason. I can however just meet that rule with
a raised area in the kitchen.

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

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?

4. There will also be a ground floor toilet with a similar offset in
the soil pipe, shorter though, so I don't see any problem there.
However it's a 8m from the kitchen so I don't think it can be used to
solve the problem in 2b. Any ideas here?

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

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


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Old September 2nd 07, 11:48 AM posted to uk.d-i-y
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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?"
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Old September 2nd 07, 08:26 PM posted to uk.d-i-y
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Default Drainage, drainage and drainage


Thanks for your reply. Hmm - in the absence of earlier replies I'd
just convinced myself 2b was better - I'll chew on it some more.

As far as the ground floor offset goes - Part H recommends a large
radius bend at the start of any offset - I can't see any reason why I
can't fit a rest bend intended for underground drainage.

It just occurred to me that the solution to the kitchen connection is
to go for 2b but connect it into the top of the ground floor
horizontal section rather than the lower part of the vertical section
- that should ensure good clearance form upstairs loo flushing and
being after the rest bend mentioned above - less likely to be affected
by any blockage.

You're correct the rainwater gullies are trapped. The old soil vent
pipe came off a branch between the rainwater gully and the inspection
pit - so it did the job of positive pressure relief.

The building is tall, 5.5m to the gutters, 9.5m to the roof apex.
Given that there's no openable windows within 3m (on that building
face) of the SVP, how tall does the SVP need to be?

Not taking it above gutter height, in fact taking it to just above the
height of the fixed lights (3.9m) would be good aesthetically.



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