Building a Manhole

gummy bears said:

I tried my best to measure the external diameter and it was more 6" than 4".

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Try your very best to measure the internal diameter of the drains next time or else you are going to waste a lot of money and time.

The external diameter of 4" salt glaze drains is about 6". As I have said before - the external diameter is irrelevant. It is the internal bore of the pipe that matters.

noseall said:

Try your very best to measure the internal diameter of the drains next time or else you are going to waste a lot of money and time.

The external diameter of 4" salt glaze drains is about 6". As I have said before - the external diameter is irrelevant. It is the internal bore of the pipe that matters.

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oh. thanks for that noseall. I did not read carefully enough to spot you said internal.

https://www.drainagepipe.co.uk/insp...-inspection-chamber-at-a-change-of-direction/

According to the top video - it says not to use the obvious entries for turning 90degrees. Instead use the straight part and add two 45degrees which will give a longer bend.

That's fine. But i need a 90 and I need to continue the flow from the other 10 houses. If I do as they say, the flow from the other 10 will be on a channel that is not in line anymore.

It's going to be impossible to hook that chamber up like that as realistically I can only chop and insert something between the main pipe and not move it.

edit: maybe I dont have to. it's not really 90degrees it's more.

You may well struggle to use a plastic chamber on a retrospective installation, without putting the existing flow through the main channel, as the side connections are higher anyway. You are permitted to use bends immediately outside a chamber, would that assist with making your required connections?

Hugh Jaleak said:

You may well struggle to use a plastic chamber on a retrospective installation, without putting the existing flow through the main channel, as the side connections are higher anyway. You are permitted to use bends immediately outside a chamber, would that assist with making your required connections?

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Thank you very much for the reply Hugh.

To be honest I dont know yet - the rain is holding me back. I need to erect some sort of covering I think.

I have had some luck in finding the right kind of materials though:

Thames water emailed me again and said I should use BS EN 13598-1 13598-2 for the IC and the same for the plastic risers.

I came across something on the net (British Plastics federation) that said:
>>BS 7158 has largely been superseded by BS EN 13598 and was withdrawn from general sale by BSI in 2013. However, this standard is quoted in Approved Document H to the Building Regulations. As such, the Department of Communities and Local Government has confirmed that it is still possible to install product to BS 7158 under the Building Regulations.<<

So Im more confident in buying items knowing the building inspectors should not make a fuss if I buy the correct BS.

I have checked the internal diameter of the main pipe - It's 6 inches. This means I have to buy a chamber that has 160mm inlets/outlets. I have asked Thames Water about using band seals and they have said ok (I only bring this up as an inspector in the past had told someone it was not suitable to use band seals).

You mention the side connections being higher (level inverts/non level inverts), I have seen some chambers (very few) that do have level inverts: what is the purpose of level and non level inverts? Which one do I need?

Thanks

gummy bears said:

You mention the side connections being higher (level inverts/non level inverts), I have seen some chambers (very few) that do have level inverts: what is the purpose of level and non level inverts? Which one do I need?

Thanks

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Either will do. Whichever best suits your scenario. We often baulk at the disparity of height between the through channel and the (higher) inlets, especially when falls are tight. It makes working out total amount of fall over a large site difficult, when entering into a chamber via one of the through channels, because you lose 100mm of fall immediately.