22 Nov 2006
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United Kingdom
I am installing a new bathroom and will be running new drainage to the shared mains drain (terraced house) at the back of the house. I have dug to the shared mains drain, and it is a clay pipe, the circumference is 63cm and approx 20 cm across. I will install an inspection chamber , 110mm underground pipe from my house to the chamber. What size would the clay pipe be? And need to be reduced to enter and exit the inspection chamber? Also would the base of the inspection chamber need to be concerted at it's base?
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Approx 20cm? It'll be either 150mm (6") or 225mm (9"). Either size is likely to be a shared sewer serving a number of houses upstream, could well be rather busy, and i'd be 99.9% sure, the responsibility (and property) of the Water Authority.

There are ways of making a connection, however under no circumstances can you reduce the size of the pipe! Doing so will cause an almightly bottleneck, probably a blockage before long, or a flood. The pipe is sized as such for its carrying capacity based on what it is required to drain!

Assuming you have the necessary permissions to make a connection, the Building Control Officer at the council will need to inspect the work. I'd discuss with him/her the prefered method of connection and chamber construction.
As above, do not reduce the bore size on the main run, rather, buy a 150mm through chamber bottom with 100mm inlets.

We would dig a large hole in the proposed chamber position.

We would then buy and get on site all the fittings, particularly the clay-to-plastic fittings, needed to 'graft- in' a chamber bottom.

It is then a case of Stihl sawing a section out of the existing pipe and grafting in the new chamber. Once the chamber bottom is in place (and concreted), you can then comfortably fit all you connections without much fuss.

You are likely to need permission from the water company to do this work.

6" (150mm) fittings are ludicrously expensive.
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There is a good guide (with pics) on how to do the job here: http://www.pavingexpert.com/drain15.htm

As previously, do not reduce the size of the through channel, you can get the plastic chambers with a 6" through channel, use of these will depend on the depth of the chamber though. They do save time, and can be a godsend if the line you are breaking into is busy as providing you have all the preparation done beforehand, they can be fitted in fairly quickly before you have a trench full of effluent..... :cry:

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