Breaking into an existing manhole

[capital1965]

I need to break into an existing manhole for a new foul water branch from my garage conversion. Is the best way to stitch drill or go in with a core drill? It is not something I have done before so any tips appreciated.

 

[noseall]

We would probably use our 'pecker'. The small wieldy roto-stop Bosh. I wouldn't envy using a core drill that low down.

 

[capital1965]

We would probably use our 'pecker'. The small wieldy roto-stop Bosh. I wouldn't envy using a core drill that low down.

Is that a small breaker type drill with roto stop? That is the sort of thing I was thinking of hiring with a core drill attachment. The IL is only about 3 feet down and the hole needs to be on an angle through the side to match the direction of flow, so I thought a core drill would give a neater hole and may be easier.

 

[noseall]

Are you going above the channel or on the same level as the channel?

 

[capital1965]

Are you going above the channel or on the same level as the channel?

The same level as the channel but coming in from slightly above it for a fall.

 

[noseall]

There will be a need for making good in any case and some bulky benching/haunching, so being careful may not be so important. What will be important is that you preserve the through channel whilst undertaking your end of the works. Be prepared for some tricky I.C. base making good.
You may need to use an angle grinder to deal with the inlet into the existing channel or completely re-hash the base.

 

[Ian H]

I'd use my pecker too. Don't forget it's going to be 2 bricks thick, you could cut the channel for a new connection with a 4" grinder if your careful.

 

[^woody^]

You need to let that core drill idea run down the drain.

If there is room, you will find it much easier to dig a big hole on the out side and work from there rather than trying to work in the confines of a manhole. Don't worry about getting a neat hole either, the benching will hide most of it, and you will need wiggle room. Hopefully you will have the type of engineers that fracture easily, but technique is everything.

 

[stuart45]

How deep is the channel?

 

[^woody^]

How deep is the channel?

About 180m near Alderney, but what's that got to do with anything?

 

[Ian H]

I think he is going to suggest an internal dropshaft.

 

[^woody^]

Even if the OP is on the south coast, BCO's won't allow it.

Btw, IL is about 900mm

 

[bernardgreen]

Is the manhole yours or is it one that the local water ( sewage ) company havew adopted ?

If it serves more than one property then the local water board will need to be informed and they may insist that they( or an approved contractor ) do the work.

 

[capital1965]

Thanks for all the replies. This project got put on hold for various reasons but I am now started work on it. The manhole is surrounded by patio slabs which sit on a 2'' concrete slab. I started digging and found a great big sheet of iron just under the slab right where I wanted to dig my hole to break into the side of the manhole. I have no idea how big this sheet of metal is and want to avoid excavating half the patio to find out, and there is a possibility, if it is more than 1.5m long, it goes under next door's house.

So to the question. Is there any reason I can't go in at the end (top left of the pic) at an angle, next to the existing pipe?

 

[^woody^]

But surely you need to dig on the outside anyway to put the new drain in?