Moving a Sewer

[lamptonpie]

First time poster, so be gentle!

We are hoping to put an extension on the back of the house (marked in red dashes), but have an inspection chamber in the way as it stands. I’ve attached a diagram of what we’ve currently got, and in my mind, a solution to this. The question is, how feasible is the alternative (the red pieces of the picture) and what’s the likely cost? A quick description of the set up we currently have:

We’re the first (maybe only) house on the sewer, with the first inspection chamber in the garage being fed by the ground floor WC. The second inspection chamber is also in the garage and has a 90 degree bend, which then sends the waste under the conservatory and to the inspection chamber currently in the lawn. This is fed by 3 more pipes – one from the utility room, one from the main bathroom upstairs and the final one which is served by the kitchen and upstairs en-suite. These then go through one pipe about 15 metres to another manhole cover where the pipe seems to go quite deep. One of the problems is that the depth and ‘drop’ between the 2nd and 3rd is minimal – they are both at about 50cm below ground level.

So my questions are:
Can I extend the pipe so that it is now outside the garage, extend the pipes from the 3rd inspection chamber to outside the extension and then connect these up to the final inspection chamber?
Would we need to drop the pipes in the 3rd inspection chamber lower and seal them in order that the footings / slab for the floor doesn’t damage them?
I assume that I don’t need to tell Thames Water as this isn’t a public sewer?
What would be the rough cost of something like this? The pipes would need to move about 8m up as you look at the picture and it’s probably 20m across from the left chamber to the right hand one.
Should I get this done as part of the extension and just let my builder do it or should I get someone more specialist to do this?

Cheers for any help

Chris

Sewers

• lamptonpie
• 19 Nov 2014
• 1

Sewers

 

[ree]

You propose to abandon the pipe under the conservatory and the MH under the proposed extension and the pipe from that MH to the far right MH?

From the second MH in the garage you want to extend thro two more MH's to the far right MH?

Why not number your MH's and indicate dimensions/runs of drainage? Also indicate the depth of the first MH and the last MH.

All abandoned sewer pipes must be packed as far as possible with a semi-dry concrete mix, and the abandoned MH must be filled, and tamped.

If the builder is competent enough to do the extension then they are competent to re-arrange the drainage.

 

[Hugh Jaleak]

All should be possible assuming an adequate fall can still be maintained on the pipework runs. Drains will need to be bridged where they pass through a wall or footing, but as Ree has said, any good builder will be able to lay drains to the required standard, and comply with regs as necessary.

Thames Water wont be interested as all the drainage alterations are within the perimeter of your property, but Building Control will need to inspect/approve the work as necessary.

 

[lamptonpie]

Thanks, will update the drawings tomorrow.

Where will be the bulk of the cost - the groundworks or the drainage materials?

 

[Hugh Jaleak]

Labour and plant will cost, plastic drainage is reasonably cheap. A bit of peagravel for bedding will also be required, but it's the time taken to excavate, lay the drains to required falls etc, and fit chambers as necessary, then backfill, man hours and plant hire/fuel is where the expense lies.

 

[Deltamale]

The easy part of what you are proposing is laying the new sewer runs and the 2 manholes (MH) and back filling the old MHs and pipes.

However you have to consider the connection of the 3 lines from the main and ensuite bathrooms and the kitchen. Each of these now needs to be run to the 2nd new MH separately and with no sharp bends that would need inspection chambers. Ideally any bends in the new lines would not be more than a swept 45º (not a short 45º). You cannot join them into one pipe to go to the new new MH as that is why that MH is there in the first place.

What is the extension for? What floor finish are you putting in the extension? Would a sealed MH cover be feasible in the new floor if it was cover with carpeting? (Just a thought)

Building Control approval is required for all drainage alterations.