Self build - foul waste connections advice please

[Weebles]

We have three pipes poking out from under our MBC slab to carry foul waste away. Existing manhole is less than 10m from the furthest point. We have had a drainage design done. Got an access point, inspection chamber and some pipe work to fit and then re-using the old connection at the manhole.

 

What pitfalls potentially lay ahead if we have a go at this ourselves? Any advice please?

 

(I should add that HWMBO did the caravan drainage so we have some “previous experience “ but that wasn’t building control inspected or for our forever home!)

 

Are we mad to take this on?

[Mr Punter]

Below ground drainage is fairly simple and can easily be DIY with plastic pipe and chambers. Let building control look at the design and see if they have any comments.

[Russell griffiths]

It will need to be inspected before you back fill it. 

Bc will soon tell you if he doesn’t like it. 

Take a couple of good pics and what you are thinking

we will soon tell you if it’s no good. 

[ProDave]

BC will also want to witness a pressure test.  Buy a pressure test kit e.g this https://www.bes.co.uk/drain-pressure-test-kit-4074

And a few of these https://www.bes.co.uk/drain-pressure-test-plug-4-110mm-1-2-test-point-1960

[Bitpipe]

Lots of practical advice here - http://www.pavingexpert.com/drainage.htm

 

I watched our guys do it - didn't seem complicated they used a disc cutter to cut pipe & chamfer the edges and soapy water to slide the pipes in. 

 

Biggest challenge will be getting the inverts & falls correct plus the effort to dig trench, lay shingle and backfill. 

[Temp]

There isn't a huge amount of flexibility in the joints and bends are only available with a limited range of angles. To make it easier to get everything aligned I'd mark it all out on the ground before digging anything. eg put the chamber bases on the ground where you think they will go and check the ports point towards where the pipes emerge from the slab. Move the inspection chambers around a bit to find a position where they line up as close as possible. Mark locations with ground marking spray paint

[epsilonGreedy]

1 hour ago, Weebles said:

Existing manhole is less than 10m from the furthest point. We have had a drainage design done.

 

...

 

1 hour ago, Weebles said:

Are we mad to take this on?

 

Is a digger hire part of your DIY plan?

[Gone West]

3 hours ago, ProDave said:

BC will also want to witness a pressure test.  Buy a pressure test kit e.g this https://www.bes.co.uk/drain-pressure-test-kit-4074

And a few of these https://www.bes.co.uk/drain-pressure-test-plug-4-110mm-1-2-test-point-1960

I have just put one of these on the BH Tool Loan Service.

[Bitpipe]

2 hours ago, Temp said:

There isn't a huge amount of flexibility in the joints and bends are only available with a limited range of angles. To make it easier to get everything aligned I'd mark it all out on the ground before digging anything. eg put the chamber bases on the ground where you think they will go and check the ports point towards where the pipes emerge from the slab. Move the inspection chambers around a bit to find a position where they line up as close as possible. Mark locations with ground marking spray paint

 

Also take into consideration paving like we didn't and end up with an IC half on and half off the main path to the house

 

We had to trim it and use a concrete paver as a lid for the part that's in the garden, then turfed over it  - still serviceable but was a PITA! 

[Weebles]

6 hours ago, epsilonGreedy said:

Is a digger hire part of your DIY plan?

 

Yes. There is some concrete (dumped after the slab pour) to get out of the way. No way am I hand digging.  Thanks for tips. Good idea to put the plans to the BC guy.  Will get level checking pronto.

 

thanks @PeterStarck for the pressure test info. Will look at that. 

 

I also recall @Russell griffiths Mentioning a chamfering took ages ago on another post so will look at that too.

 

thanks all. Looks like we’ll be able to do it, with all your help ?

 

photos will follow over the next few weeks....

 

 

[Weebles]

Having looked at levels it looks like we’ll need to encase the foul drainage pipes in concrete (our cover is less than 600mm. 

I have no issue mixing up some concrete but how do you hold the pipe in place? Could some holes through the expansion boards at the joints work? How do the pros do this?

Its not a long length of pipe to do (foul waste only at the mo. The surface water drainage is another problem for another day)

 

[PeterW]

Tbh it’s normally bedded with 20mm and then encased on top / around the sides and job done. 

[Oz07]

The mix isn't wet. It's more like a kerb mix. Set your fall up with conc bed then put pipe on the fill around and on top