replacing clay sewage pipe from toilet

[andreas]

My bungalow appears to have a raft foundation below the floorboards. Either that or it has no foundations at all!. I have to replace some of the old clay drains in the garden as they have broken. While I am doing so I would like to replace the toilet waste.

At the moment, the toilet waste is 12 inches to the centreline away from the wall, so the pan sits out a very long way into a room which is already cramped as it is. Lifting the floor boards it looks like the pipe was originally much lower and has been extended upwards with a cemented in section and is over 2 inches proud of the floor so I cannot even replace the bottom-exit toilet fitted with a bottom outlet

Would it be safe to just core drill a new waste through the slab behind where the clay pipe is currently? What do I need to consider when doing so? If that is a bad idea what are the chances of breaking off the extension and cleaning up the original end of the clay pipe and then adapting that outside to the new plastic pipe?

Grateful for any suggestions. 

[ProDave]

I would want to be taking a section of the slab up and replacing the lot in new plastic pipe. Including the run under the foundations.  Then you can get it as you want in the place you want.

[saveasteading]

Cutting out the slab probably won't be too tricky, and removes the worry of previous bodges.

[andreas]

23 hours ago, ProDave said:

I would want to be taking a section of the slab up and replacing the lot in new plastic pipe. Including the run under the foundations.  Then you can get it as you want in the place you want.

How big a section would you be thinking, and what would you see the advantage being in cutting the slab rather than using a core drill to make the hole where I want? I have dug out the other side of the wall to have a look, I can get a plastic pipe in from above, and a bend in from below relatively easily. I'm just worried about disturbing the slab too much!

 

[Mr Punter]

You can break out a fairly large area of slab without issues.  The slab could just be concrete oversite.  Hopefully there is no rebar / mesh.  Better to have a bit of wiggle room.