2 gulleys in line

18 Jun 2011
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United Kingdom
hi guys, were about to have some drainage work done. the builder has opted for 2 gulleys, 1 for sink waste connected in a line via 50mm pipe to the other which is for shower waste and roof drainage. this is then forwarded around a bend to an access chamber, 100/110mm inlets. There is also a toilet attached to the chamber.

1. Will the water flow between the two gulleys so long as there's a 1:40 drop ?

2. The gap between the gulleys will be 4m, if its longer will a 60mm pipe be required ? The pipe will be underground i guess, does it need a section for it to be roddable .. or can you do this from the gulleys ?

The inspector of course will be coming to check when the area is dug up but all connected. Cheers.
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I'd be very surprised if Building Control will pass a gulley with a 50mm drain, it needs to be 110mm. Sink waste will carry fat, grease, laundry detergents etc, 50mm in that application is a complete bodge and is likely to block very easily!

Using 'bottle' gullies will provide adequate rodding access, it's built into the gulley. Could you post a diagram of what you're proposing to do, should be better able to advise from that.
hi Hugh, if thats the case ill make sure its 110mm(The orange/brown colour) and make sure gulley 1 and 2 are bottle gulleys. The red sections are all new. The existing 7m section should provide enough fall of 1:40 into a combined system, Another gulley and the existing soil pipe all join to it - its a 6 way which is joined to next doors as well. Currently there's roof drainage/sink/washing machine going into that existing gulley connected to the manhole with 100/110 clay pipe. Thank you.
Yes, all underground sections need to be 110mm. Bear in mind if it's a combined system, and you are losing the existing gulley taking the roof drainage, unless you are building a soakaway, the rainwater will need to be connected via a trapped gulley. Direct connection of a rainwater pipe to a combined system wont be allowed.

The pan can be directly connected to the drain if thats preferable, (assuming its ground floor), the stubstack isn't strictly necessary there unless you are proposing additional waste connections. Access is available to the pan connection from the proposed new chamber.

I'd also fit either a small chamber or at least a rodding eye rather than the 90deg bend on the corner. You may never need access there but it's then available in future should the need arise. (I'm doubtful whether the BCO would allow the bend and in any case, rods wont go round a 90deg corner!)
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1.In the diagram, should gully 2 be a trapped gully. so then move the rain water pipe to that side. would that be ok? would sink waste water still be ok to route into this then. I thought you could just site the rain water pipe over the bottle gulley, in the wickes guide they say its ok fig. 5/6: http://www.diydoctor.org.uk/project_images/undergrounddrainage/underground drainage.pdf.
The rainwater pipe from the existing gully(im guessing now its a trapped one) can be routed to the new roof area.

2.It is ground floor yes. For the corner can i used a 92.5 degree access bend ? it would allow rodding in both directions i assume- if you remove the cap inside gully 1 which is a bottle gully with a rear inlet. just making sure when the inspector comes that i don't have to get things changed. Thanks Hugh big help.


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