Building a Manhole

[gummy bears]

Dear All,

I have to build a manhole – Thames water state you must use like for like materials only, in this case it means clay.

The pipe I’m tapping into is 150mm clay.

Rather than use clay channels and benching (if that’s the right term) – I found this

https://www.mytub.co.uk/supersleve-150mm-obl-acc-junction-sja3r-product-574137



Would this be suitable?

The pipe is about 1.1m deep

I’m also thinking of using precast chambers


https://store.jdpipes.co.uk/600-450...KBth6cMH0UlTX8Uq219cxRFOVwv1OQG4aAju2EALw_wcB

Thanks

 

[^woody^]

You need to use a proper channel and bends and not that junction.

Can't you use a plastic chamber complete? they've been all the rage since the 80's

 

[gummy bears]

You need to use a proper channel and bends and not that junction.

Can't you use a plastic chamber complete? they've been all the rage since the 80's

Thank you very much for the reply - you have saved me from a costly mistake.

What's the access junction for then?

If you are talking about plastic inspection chambers - I'm guessing not, as it's not clay (like for like and all that). Plus they are smaller maybe at 450mm vs 600mm. So I'm not sure if Thames water will be happy.

I will be using 2 plastic inspection chambers on my private pipes though further up.

So by proper channels you mean like the one I have currently in this photo?

Is there nothing ready built I can buy? Like the plastic chamber but in clay? It's going to be a nightmare building this in this weather - plus the ground water is level with that pipe! You pump it out it just comes back.

edit - I wonder if I even need a manhole there, as there never was before. The pdf is the proposed plan I did of the pipes and submitted to Thames Water and they approved it. As you can see originally there was no man hole at the similar junction.

 

[^woody^]

So I'm not sure if Thames water will be happy.

You need to ask them. All plastic drainage is BBA approved, so no reason not to use it - it's not a problem with any water company I've been involved with.

That junction is for limited access where the pipes are nearer the surface. You wont get rods down and through that fitting at 1.1m deep

 

[gummy bears]

You wont get rods down and through that fitting at 1.1m deep

I see.

 

[gummy bears]

You need to ask them. All plastic drainage is BBA approved, so no reason not to use it - it's not a problem with any water company I've been involved with.

That junction is for limited access where the pipes are nearer the surface. You wont get rods down and through that fitting at 1.1m deep

Traditional Brick Manholes
Chamber bases can also be installed into wider, brick built traditional manholes. The benefit of this is that no benching is required - the chamber base provides the flow channels and the connections to the incoming and outgoing pipes.

​

I found the above from a web site that sells plastic chamber bases - maybe I can have a plastic base but build a brick manhole around it?

edit. Thames water emailed. hope I get a speedy reply.​

 

[Hugh Jaleak]

You can use the plastic base, then build a brick or concrete chamber above it, as Noseall says, it's the way it's done these days to save on labour. Also handy when working on live pipework, no waiting for anything to go off before reinstating the flow. Check Thames will accept your plans before going ahead though!

 

[^woody^]

Why would you want to use a plastic base than then still have to go through the palaver of making a concrete slab around it and under the pipes and building a brick chamber?

If you are using a plastic base, if you can use a plastic base then you can and may as well use the plastic risers too.

 

[gummy bears]

Why would you want to use a plastic base than then still have to go through the palaver of making a concrete slab around it and under the pipes and building a brick chamber?

If you are using a plastic base, if you can use a plastic base then you can and may as well use the plastic risers too.

Thanks for the reply woody.

Yes absolutely - if it's allowed. I guess only Thames water can give me the answer to this or someone who has dealt with the same situation. Should get a reply from Thames Water within a week


Their specification says like for like - if I accept that, I have to go clay and brick.

I'm only trying to avoid clay channels as benching might be tricky for me in this weather and the thing sits in ground water.

As for the pipes I would have liked to use clay for most of the long runs as I have read they are more forgiving if you have not bedded them correctly vs plastic.

 

[gummy bears]

You can use the plastic base, then build a brick or concrete chamber above it, as Noseall says, it's the way it's done these days to save on labour. Also handy when working on live pipework, no waiting for anything to go off before reinstating the flow. Check Thames will accept your plans before going ahead though!

Thanks for the reply Hugh.

Yes that's another thing - it is live and serves about 10 other houses.

 

[Hugh Jaleak]

The 'ground water' may well be the existing sewer leaking, looking at the pic. Be careful how much you let Thames see, before they start getting ideas about lining it or something.

I have come across jobs where the use of a plastic base has been permitted, but the chamber has had to be constructed from concrete rings, mainly due to depth of invert, but depends what the spec is they insist on or how picky the Inspector wants to be.

I cant tell from the drawing, but if you are building over the 2 (blue) pipes coming in from the neighbouring property, these may need to be diverted around the footprint of any new building.

 

[gummy bears]

The 'ground water' may well be the existing sewer leaking, looking at the pic. Be careful how much you let Thames see, before they start getting ideas about lining it or something.

I have come across jobs where the use of a plastic base has been permitted, but the chamber has had to be constructed from concrete rings, mainly due to depth of invert, but depends what the spec is they insist on or how picky the Inspector wants to be.

I cant tell from the drawing, but if you are building over the 2 (blue) pipes coming in from the neighbouring property, these may need to be diverted around the footprint of any new building.

Thank you for the reply Hugh.
still waiting for Thames water to reply.

As for the ground water I actually called them over as I thought I might have damaged the pipe. They came over and used coloured dye and cctv - all they said there was no damage and he's pretty sure is not sewage.

That plan was sent to Thames water and approved, not sure if I could divert around the new building, unless I dug up neighbours garden.

 

[gummy bears]

Why would you want to use a plastic base than then still have to go through the palaver of making a concrete slab around it and under the pipes and building a brick chamber?

If you are using a plastic base, if you can use a plastic base then you can and may as well use the plastic risers too.

ok Thames water have replied

>>>We would require anything on the public sewer to be like for like ie so if it is currently clay we would need the pipework or any connections to be clay. We would how ever accept a plastic Inspection chamber.<<<


Surprisingly to me, I think that's a yes for the plastic inspection chamber.

The reply was very short - it said nothing about the risers. It said nothing about the fact these chambers are 110mm and the clay pipe is 150mm. Are there 150mm chambers?

Do I just use a clay reducer?

It will make things very easy if I'm allowed the plastic risers.


edit. i could probably use the rubber reducer things

 

[noseall]

The reply was very short - it said nothing about the risers. It said nothing about the fact these chambers are 110mm and the clay pipe is 150mm. Are there 150mm chambers?

Do I just use a clay reducer?

Are you sure your (internal bore) drains are 150mm? They look like regular 4" (100mm) fellas to me.

Anyhoo, you cant reduce 150mm down to 100mm and then back up again - no. You can however get a chamber with a 150mm through channel with 100mm inlets.

It will make things very easy

​

Drains are rarely 'very easy'. I prefer to use the term less difficult.

 

[gummy bears]

Are you sure your (internal bore) drains are 150mm? They look like regular 4" (100mm) fellas to me.

Anyhoo, you cant reduce 150mm down to 100mm and then back up again - no. You can however get a chamber with a 150mm through channel with 100mm inlets.

Drains are rarely 'very easy'. I prefer to use the term less difficult.

wow wee - 150mm through channel, this job keeps getting less difficult! if only it would stop raining. I tried my best to measure the external diameter and it was more 6" than 4".

Are you allowed to post a link of one such base? I have done a search for 150mm chamber before I knew they existed but and nothing much came up. I'll try again.

edit: i think i found one '
Chamber Type 160mm Inlets and 110mm Outlets

https://www.drainagesuperstore.co.u...able-inspection-chamber-base-160mm-110mm.html


https://www.drainagepipe.co.uk/insp...mm-inlets-and-outlets-450mm-diameter-p-6D900/