Diameter of underground soil pipework

[Mungo]

Hi Folks, To provide drainage to our new en-suite requires a new vertical soil stack and also a connection to the soil pipework in the ground outside. I've managed to excavate the soil and discovered the (1970's) old pipework. Holding a ruler across it shows an external diameter of five inches.

The Screwfix catalogue (but not the website) mentions diameters of

110mm and my guess is that's the internal diameter of the pipework, but all I have to look at just now is the outside diameter of a clay pipe.

Sacrilege I know, but SWMBO has decreed that for this job our tame plumber ought to be remunerated. I'm curious though - with a well-secured clay underground pipe how do you wrestle a T-piece onto it? My only presumption is that a section of clay is cut out of length with the new T piece and "collars" are slid down the pipework across the cut ends to ensure integrity of the joint?

If so, how much soil need I dig out to give the plumber sufficient room to work in?

No doubt there will be further questions... thanks in advance.

Mungo

[Lobster]

is your friend here - the stock all manner of adaptors to connect different sizes of pipework.

David

[Tony Bryer]

110mm is the outside diameter of a PVC soil/drain pipe: 4" (102mm) internal bore, as for your clay pipe.

You can connect into an existing run in a number of ways including:

1. Form a manhole base around the pipe at a suitable point, cut away the top half of the pipe with an angle grinder to make a channel and then complete the manhole. Best option if you need to keep the drain in use (perhaps because it's communal)
2. Cut out a section of pipe and use clay to PVC adaptors at each end, lengths of pipe and a slip collar (well lubricated).
3. Cut out shorter length of pipe and use stainless steel/rubber connectors to seal to new tee.

[Mungo]

Thanks for the reply Tony (you can see I've come back round to the problem since the "tame plumber" ain't returning my calls just now :-)

Were I to do the job myself, how does the following loose set of instructions sound:

1) Buy a 110mm 87.5 degree T piece (with three sockets on it) and a length of 110mm pipe and a pair of those rubber couplers with stainless steel "jubilee" clips.

2) Cut short lengths of the plain pipe to engage fully in the "straight through" sockets of the T piece and to stick out by half the length of the rubber coupler.

3) Assemble the T piece with its two stubs of pipework, then transfer this length down on to the existing clay pipe.

4) Ensure that no-one will be in dire need of the loo for the next hour (or provide a suitable bucket ;-)

5) Block off the upstream section of the sewage pipe (pipe is solely for use of my property). I thought that putting a balloon in a thicker carrier bag and inflating it in the pipe might make for a strong enough "bung"? But is this overkill?

6) Stick a garden hose down the other side to wash away any in-pipe debris that may surprise me later.

7) Use either a small angle grinder OR a hacksaw with carbide blade to chop out a length of clay pipe equal to the length of the new T piece (and its protruding stub pipework) I guess I ought to go hire a diamond cutter but I'm mindful of the pennies...

8) Tidy the ends of the cut pipe, slip the couplers over each end, put the new plastic T-piece in situ and slide down the slip couplers and tighten suitably but not over-tighten.

9) Perhaps temporarily block off the stem of the "T" piece and then run the garden hose again to test the connection.

10) Connect the rest of the pipework then phone the Building Control Officer and gloat... :-)

11) Remember to remove the bung.

Have I missed anything (apart from filling in the groundwork with pea gravel)?

Mungo

[Lobster]

Well: "tame" and "plumber" - two words you don't normally see in the same sentence...!

David

[Tony Bryer]

[snip]

Sounds pretty good to me. Most older clay drain pipes are pretty soft and cut like butter. The newer plain end pipes are a different matter though.

[Set Square]

Why not use a T-piece with a pipe rather than a socket on the outlet side? (like this:

) That would save using a stub pipe that end - your rubber coupling would go straight onto the end of the Tee.

[Mungo]

Neat idea: thanks. Showing my ignorance again here: is this make of pipeware available through the builders merchants or can I wander up to a B&Q warehouse and purchase it?

Mungo

[Set Square]

Don't know about B&Q - but BMs certainly, and probably Wickes. Several firms make this type of thing - but the pipe diameters are standard, so you can mix and match if required. The brown stuff is for below ground and grey for above ground.