Underground waste pipes / drains

5 Nov 2008
Reaction score
United Kingdom
I've lifted some concrete and the photo shows what I've got at the moment.

I would like to add a drain at the base of the downpipe from the gutter on the left hand side of the photo. It’s an old house and rain and soil waste are combined.
The wall to the left of the photo is the kitchen, the wall at the back is an extension. Kichen waste enters the drain in the corner above the water trap. The vertical pipe in the corner is a cast iron vent pipe (up to roof height) that is connected to sewer via a pipe that loops around the drain and connects to the junction in the middle of the picture.
I would like to connect the downpipe to the drain via a bottle gully fitted approximately where the junction currently is. This means a few changes to the current layout are needed. I am confident of being able to do the job, but have a few questions to determine which way I should tackle it.
1 The cast iron vent pipe is cracked in several places and is dangerous. I want to get rid of it if possible (or replace it if necessary). Is the vent pipe needed?
2 The kitchen waste pipe would then be upstream of a bottle gully. Is this a problem or should I use a spur off the main pipe to the base of the downpipe so that the kitchen waste cannot get trapped in the gully?
3 Should the kitchen waste enter upstream of a water trap where any debris/cooking fat etc sits in the open drain (as now), or would it be better to feed it straight into the sewer? If the latter, the only thing stopping noxious smells from the sewer getting into in the kitchen would be the water traps in the sink. Is this ok?
Any thoughts/comments welcome.

Sponsored Links
I've done a bit more digging and have a better idea of what I need to do, but I'm not sure about the vent stack. The pipe run is about 6 metres and empties into a manhole. There are no toilets emptying into the pipe, only kitchen waste and rainwater via gullies. Do I need a stack?
Second question:
The kitchen waste comes out via a 4" clay pipe just below ground level and the socket shoulder is flush with the outside of the wall. Unfortunately the lower part of the socket is smashed and the waste water soaks into the ground. I can cut the pipe back so it is flush with the wall, but how do I join to it? Is there a coupling or sleeve that slides inside the ceramic pipe? I know this would create a slight step/restriction, but it has to be better than what I've got.
Any thoughts?
Go on then I feel sorry for you, that picture looks what ive got outside my back door and have been putting sorting it out off for ages.

The vent is the top of the drain and even though there are no WCs on your run there has to be a vent (thats why its there).
As for repairing damaged pipes, cut with desc cutter and place 110mm plastic pipe in between damaged parts using correct rubber fittings (they change size and have big jubilee clips) dont worry to much about the step it creates inside.
As for running drain right into extension, fine providing everthing is sealed correctly with correct fittings to go from 1 1/2 to 4inch.
You will get all you need for drainage at a good building merchants.
Suppose you should consult building regs before altering a drain but that could be opening a can of worms. :cry:

Have fun ;)
Thanks for this.
I understand the need for vents, but I think this pipe may be left over from a previous incarnation of the house when it was converted to flats. There was a basin in a bedroom that fed into the vent pipe and used it as a waste pipe. However, this is no longer the case and the pipe now serves purely as a vent.
I should have mentioned that the pipe from the downstairs toilet at the back of the extension has no vent and works perfectly well. Also, the sewer is vented elsewhere via the main bathroom/toilet soil pipe. Does this change the need for a vent on this pipe?

As for joining accessible clay pipes to plastic, I don't have a problem with this, but the pipe from the kitchen is set in the wall and broken. How do I join to it? (I don't think I'll like the answer though!)
Sponsored Links
Either dont use the pipe going under the extension and fit a gully outside and run wastes to it or fit a pan connector into the end of the broken pipe.
Not ideal i know but if its a clean break works quite well.
The new plastic pipe will fit in the other end.
As for the other loo having no vent, its classed as a sub stack which needs no vent.
The head of the drain does however need venting.
Thanks Cider,
I'm going to fit a gully to replace the one that's there and use a ribbed adaptor (similar to a pan connector) to connect it to the broken pipe. I just hope that the step doesn't cause blockages (the kitchen is the next project on the 'to do' list and we want to move the sink so hopefully this fix is only temporary).
I'm still not sure about the need for a vent though and I've done a bit more Googling. According to the Brett-Martin website, "Ventilation is necessary if the distance from the highest appliance connection to the stack to the invert of the drain is in excess of 2m, or if the distance from the crown of the WC connection to the invert of the drain is in excess of 1.5m. "
As there will only be two gullies at ground level feeding the pipe and the manhole it feeds into is less than 50cm deep and is vented by a separate stack, I can't see the need. What make the downstairs loo classify as a stub stack but another branch with two gullies on it not classify as a stub stack?
I'm confused!

"Ventilation is necessary if the distance from the highest appliance connection to the stack to the invert of the drain is in excess of 2m, or if the distance from the crown of the WC connection to the invert of the drain is in excess of 1.5m. "
Theres your sub stack.

Unless you know where the rest of the drains run in your row of houses and know which are vented, I personally would keep the vent.
I really am confused now :(. What do you mean by 'theres your sub stack' following the quote from the B-M website? My interpretation is that as I have no appliances on either branch and the only WC connected is no more than 0.7m above the invert, a vent is not needed. Have I missed something?

Fortunately however I do know where the drains run - it's a Victorian house, not a modern development and the drains from my house are for my house only. I've attempted to sketch the layout which may make things clearer.

In summary, I want to install a gully where the yellow dot is and (hopefully) remove the vent pipe marked with a red dot. There will then be two gullies on one branch and a toilet and gully on another, all of which are at ground level and less than 1m above the invert. The system is vented via the soil pipe from the bathroom (green dot) before it flows off my premises and into the main sewer under the road.

Does this make it clearer? If so, do you think I need the (red dot) vent?

Job done. Needn't have worried about the vent, it's existence was superfluous as there was about 50 years of rust and twigs in it.
The old clay system came out easily and the new pipes connected without a problem. I'd set aside the whole weekend to do it, the gullies were concreted in by Saturday lunchtime!
The vent pipe took about 30 mins to remove using a ladder (I'd forgotten how much I hate heights), a rope and a FBH.
It's good to have a productive weekend, makes a change from going to work :).
Out of interest, is there no vent on the run from your downstairs wc to the manholes? Thought there had to be one to prevent a vacuum being formed which could (in theory) lose the trap seal in the pan
No. The only vent is the one on the soil pipe from the upstairs loo, about 10m from the downstairs loo. I've lived here for 7 years and never had a problem even with the vent pipe (now removed) being blocked.
Having thought about it more, what could cause a vacuum sufficient to drain a toilet, apart from flushing the downstairs loo itself? As I said there are no other houses on our drains.


DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links