Bedding new inspection chamber

[SparrowHawk99]

Hi everyone, I'm nearing the end of a difficult job fitting a new IC.

I've bedded the pipes in pea shingle and the inspection chamber is bedded also, but there is slight movement as you would expect with pea shingle.

I wasn't sure whether to concrete in and around the chamber or just backfill and then repair the 250mm concrete slab above. I can't see why it would be necessary to concrete in and around the base of the IC but perhaps I'm wrong?

I'm also thinking perhaps concreting around the pipes is bad if ever I wanted to re-dig the area.

Hoping someone can give me some pointers to finish this job. The existing pipes were clay

P.S I know how to repair the DPM before concreting so no need to tell me

 

[Hugh Jaleak]

I would whack some concrete around the base of the chamber to hold it in position, but leave the couplings free either side onto the clay to provide for any slight movement in the drain. Concrete will ensure the chamber doesn't move whilst you backfill.

 

[SparrowHawk99]

I would whack some concrete around the base of the chamber to hold it in position, but leave the couplings free either side onto the clay to provide for any slight movement in the drain. Concrete will ensure the chamber doesn't move whilst you backfill.

Any suggestions on how to do this? Will be hard keeping the concrete from the couplings unless I knock up some formwork but will involve a lot of buggeration I can picture it now. To be clear, does the concrete only need to be around the sides and not underneath?

 

[nickjb]

I did quite a dry mix and trowelled it into a heap so it came up the sides of the chamber base a little bit but didn't get to the ends of the spigots. I used a couple of offcuts of ply as really rough shuttering, it's not like pouring a slab. My base had some fins on the bottom that sat into the concrete. Seemed to hold it quite nicely and it didn't budge while back filling.

I also did an air test on each section before backfilling and a water test on the whole system once it was partially backfilled. Didn't want to dig it up again.

 

[noseall]

Once you have the chamber bottom and all connections in place, you would then carefully ram concrete under the chamber bottom into all the nooks and crannys being carful not to actual lift the chamber.

Clear the concrete away from potential inlets.

Pop a riser on and check with a level.

Job done.

 

[SparrowHawk99]

I did quite a dry mix and trowelled it into a heap so it came up the sides of the chamber base a little bit but didn't get to the ends of the spigots. I used a couple of offcuts of ply as really rough shuttering, it's not like pouring a slab. My base had some fins on the bottom that sat into the concrete. Seemed to hold it quite nicely and it didn't budge while back filling.

I also did an air test on each section before backfilling and a water test on the whole system once it was partially backfilled. Didn't want to dig it up again.

Thanks everyone.

Nick can you explain to me how to air and water test please?

 

[nickjb]

Probably better explained here: http://www.pavingexpert.com/drain11.html

One tip to add. Tie a bit of rope to the bung, if it disappears down the pipe you might have a problem.

 

[Hugh Jaleak]

You'll probably find the old clay drains will leak like a sieve, wouldnt worry too much about a test personally.

 

[noseall]

You'll probably find the old clay drains will leak like a sieve, wouldnt worry too much about a test personally.

Ditto.

Just make sure all your connections are 'home'.

 

[SparrowHawk99]

Christ Well a lot there for me to look into.

Just finished channeling out the new waste for the sink at the other end of the room. Had to take out a 3 metre run of 200mm wide channel of 250mm thick concrete. Ran a grinder down the sides and covered the house in sh1t and then sds drilled down to the DPM without trying to puncture it. Also found the electric mains cable does a 90 degree bend exactly where the new pipe is going to fit into the chamber, so another hours work tomorrow moving that ****ing cable up a notch after breaking out more concrete and doing a careful dig and then I'll be able to bed the chamber, fit the other connection (1 days work) and then FINALLY I'll be able to test the system and find its pouring out everywhere and basically that I'm ****ed

 

[SparrowHawk99]

Quick question for anyone still paying attention..

At what point does brown become grey?

I've got 2 entrys, one is a kitchen sink waste only deep enough for one up bend, do I use grey or brown bend, as bend will penetrating FFL of concrete?

Same question, for bend of main stack, do I connect grey or brown straight to the base bend which is brown, as this will penetrate FFL ??

Thanks in advance

 

[Hugh Jaleak]

I doubt it'll pi$$ everywhere, but old clay pipes aren't always in the best of condition after so many years, whilst they'll continue to fuction adequately for many years yet, asking them to pass an air test is somewhat ambitious!

To perform an air test, you would bung any open ends, then using a manometer (U gauge), put a slight positive pressure into the pipe, and watch for any pressure drop on the gauge. Fine for new work, but really wouldnt concern yourself with what's already there. Providing there's no visible leaks from the joints then that'll do IMO.

Golden Brown (underground stuff) will be fine internally above FFL, (unless you prefer looking at grey!). Golden Brown should not be used above ground externally as it isn't resistant to the UV in sunlight. (If left exposed it will soon fade and become very brittle). Grey (and white/black/brown above ground stuff) offers better protection to sunlight, hence more expensive.

 

[SparrowHawk99]

Thanks again Hugh, one minor irritation I've come across is can't seem to find brown in less than 3m lengths, which is really annoying because I've got a small car. Had loads of funny looks last time I was transporting 2 lengths of straight pipe in the car, 400mm of it was sticking out the window lol The grey comes in 2ms.

Will thank you guys once I'm done with this job and some pics on the way - internet connection won't let me upload at the moment

P.S I'll have a go at the test because I like gadgets! Out of curiosity is this the same sort of test they use to detect leaks in small dia supply water pipes?

Also, for the pipes I have cut I'm using a little hack saw but cuts aren't remotely square, what's the trick to it?

 

[Hugh Jaleak]

Pipe at Screwfix, 2x3m brown (underground) is £17, 2x3m grey (above ground) is £32! Take saw with you, just dont cut it too short in the first place!!!!!

Guide to testing: http://www.pavingexpert.com/drain11.html

Good saw (if cutting a lot of plastic) is something like: http://www.stanleytools.co.uk/product/147297 or use an old wood saw for occasional jobs. (Plastic soon blunts a wood saw though.) You'll struggle to get a square cut with a small saw.

 

[SparrowHawk99]

Can never be simple for me... stack does not line up over the 3 floors, to have it in the corner of the ground floor, I have to have the stack in the basement about 100mm from where I want it, my question is..... will it cause me problems down the line if I fit a 0-30degree adjustable bend mid floor to give me the angle???

I can imagine solids (poo) traveling down that stack from the bathroom on 1st and smacking that turn in the pipe and splattering along with the bog roll, and potentially causing nasty problems. I've got the option to have a straight run, maybe I should?