Bends in vertical running waste pipe

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My existing waste stack runs up my gable end wall. I am having a storey side extension, so the waste stack will end up in bedroom.... not a fan of this.

I want to turn the waste immediately downwards out of the toilet into the bathroom floor and into the space between the joists. I then want to turn it 90 degrees and through the gable wall between the joists. Once through the gable wall it will be above the garage ceiling. I then want to turn it 90 degrees again to bring it through the garage ceiling and into the stack. The stack will be removed from above, and an AAV fitted in the garage. It will be roddable.

Will this work.....
 

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Altering waste pipes comes under building regs, so that's the route to take. This is covered in Approved Document H
 
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Not the best idea to remove an existing Open Vent and cap it with an AAV, can cause more issues than it solves. Regs also require the highest point of the drain to be vented, drains need to breathe.
 
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There is/will be another waste stack on the new external wall that is connected to the same manhole..... this one will be open vented. I'll have to speak to building control to see if its acceptable or not. If its not, not sure what I'll do.
 
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Can you look at moving the stack into a corner and continuing upwards if need be? Dry section can be reduced to 3" (82mm) if need be and can have as many bends as you like!

Also need to note, if going down the AAV route, the Valve needs to be above the spillover level of the highest appliance, (usually the basin).
 
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Can you look at moving the stack into a corner and continuing upwards if need be? Dry section can be reduced to 3" (82mm) if need be and can have as many bends as you like!

Also need to note, if going down the AAV route, the Valve needs to be above the spillover level of the highest appliance, (usually the basin).


Not really - I'd have to box in a waste pipe horizontally over to the corner of the bedroom. The toilet waste height is currently coming through the gable wall about a foot above the new 1st floor height. I'd have to box this is too - I'd end up losing too much space in the room. Its aint that big to begin with.

I've definitely seen AAV's much lower than that. If I were to keep the valve above the height of the bathroom basin, it wouldn't be far off the height of the existing stack.

Suppose I'll have to speak to the BCO and see what he'll allow.
 
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You may have seen AAV's lower than that but doesn't mean they're right. Idea is, if the pipework blocks up, waste cannot spill out of the AAV unseen and cause an unholy mess before anyone realises. Your choice, we'll only tell you how it should be done.
 
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It would look like your proposed extension has joists running same right way to maybe take drain through to new outside wall and then vent correctly?
If so just put a junction in correct place to connect W C.
 
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The aav will be in the garage and won't be boxed in..... if that makes a difference...... don't suppose it does. Can you connect a waste stack around a corner? I have another waste stack at the back of the house that is currently exposed down to a depth of about 1 meter below the ground not been backfilled yet. Could I run a new stack from the new gable end wall, rest bend below ground level turned 90 degrees to take it to rear. Then another rest been taking it round the corner and into the stack at the back? The correct gradient can be achieved all below ground. I could then take the waste out to the new gable wall in between the joists - there will be enough fall
 
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The aav will be in the garage and won't be boxed in..... if that makes a difference...... don't suppose it does.

No, I'm afraid.

Could I run a new stack from the new gable end wall, rest bend below ground level turned 90 degrees to take it to rear. Then another rest been taking it round the corner and into the stack at the back? The correct gradient can be achieved all below ground. I could then take the waste out to the new gable wall in between the joists - there will be enough fall

Yes, no reason why not and sounds like possibly a superior solution. Only issue would be, you will need chambers at each change of direction, not bends. As the new run isn't too deep, the smaller Mini Chambers would suffice, use a 45° bend on each end of the through channel to give a 90° turn.
 
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Waste run.jpg
Kind of like this..... so you think using chamber at the corner will suffice? How does the vertical pipe enter at the base of the gable wall? Or will a rest bend there be sufficient into a chamber at the corner
 
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This is the connection on the back wall of the house..... as it is at the moment. You can't tell, but its at least 1 meter below and is now encased in concrete so can't be moved.

The one near the blue pipe.... not the old clay one.
Screenshot_20211206-213354_Video Player.jpg
 
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Rset bend at foot of stack, continue to corner, turn 90° with a chamber, continue to meet existing drain, turn 90° with second chamber and couple onto existing drain. Ideally find and cap off redundant drain outside footprint of property if possible.
 
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Thanks Hugh..... thats great.

Would i not get to the back corner, turn it 90 degrees so its running towards that sewer pipe then just connect onto it with a 90 degree elbow on top of that pipe that's sticking up out of floor.

I'll use the other connection to connect a downstairs loo. If I did that, and used an aav on it for a downstairs wc, would the aav still have to be above the 1st floor basin..... or just the ground floor basin as it will only be the downstairs wc connected to it
 
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