Can I use a sewer mini access chamber?

4 Aug 2012
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United Kingdom
Checking the Screwfix catalogue and see there are two types of ready made sewer chambers, the 450mm size and 270mm size.

I need a new chamber for my house, where a 4" pipe will join into the sewer leading to the public sewer chamber. Also a rainwater down pipe will need to join in to the chamber on the same side. So can I use the 5-inlet mini chamber, which would save me a bit of money. Adjustable mini chamber, 2 x risers and frame and cover = £64, Adjustable 450mm chamber same spec = £124, so the larger chamber is twice the price.

Also what advantage does the adjustable chamber give me over the fixed units?.

With the rainwater down pipe, what do I need on the bottom of it? Is it a low back P trap with a hopper above it???

Apologies for all the questions, but I know there are experts on here with good advice - thanks
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Depends on the depth of the invert of the sewer. The mini chamber can be used for an invert up to 600mm deep, between 600 to 1200mm the bigger chamber is needed. You need to allow access for rodding should it be required, using a mini chamber over the 600mm depth would make it extremely difficult to bend the rods into the required branch. The adjustable inlets give you some flexibility on the connections, if not exactly in a straight line to the chamber. (Building regs permit use of a bend immediately outside a manhole.)

Provided you have permission to connect rainwater into a foul sewer then my personal preference would be use of a bottle gulley. Easier to clean out then a P trap, and also allows rodding access to the pipe beyond the gulley should it ever be required.
Thanks Hugh,

I will be less than 600mm so I will use the smaller chamber and save a few ££'s. The adjustable inlets should provide me with a bit of flexibility as I'm joining some old pipes to new.

P trap Vs bottle gulley - Is there any regulations on this at all that I need to be aware of? Will the buidling inspector accept both?
I would think Building Inspector wont mind which gulley you use. I prefer bottle gulleys as they're usually easier to clean out, and rodding access is provided within the gulley. (Either remove centre section or small plug in outlet depending on manufacturer.)

Plunging a blocked hopper/P trap gulley usually results in water/sludge/whatever else is decomposing in there, splashing everywhere. :evil:
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