It may be info overload like Tamz says, but here is a bit more to try and answer your questions.
82mm is about the equivalent of 3" or 75mm in certain makes.
So why soil instead of rain water pipe?
Well 82mm Hunter soil has 3.2mm thick walls and their rwp has 1.80mm - 2.05mm. BS EN 12200 is even thinner.
So basically the walls of the soil pipe are thicker and so probably able to stand up to more thermal shock than RWP.
The next bit about expansion:
A PVC pipe expands and contracts like mad. 🙂
So to stop it moving all over the place, they use collar clips around the pipe collar to provide an anchor point.
The other clips are usually known as barrel clips because they fit around the barrel of the pipe. They are intended as guides for the pipe as it expands not for anchor points to control expansion.
If you anchor a pipe at its collar then it can only move downward into the next lower pipes collar.
To stop it forcing down onto the bottom of the lower collar, you pull it back about 15mm or so to allow for expansion. Then you fix the lower collar as an expansion anchor point and so on down the stack. In between collar's you put barrel clips to keep the pipe in line.
In effect you have fixed a piece of pipe between two fixed points and cut it short to allow for it to get longer as it heats up.
But don't forget to use silicon grease on the pipe ends, washing up liquid makes the rubber seal ring bond onto the pipe and after a few weeks you virtually need a lump hammer to knock them apart 🙂
If the rubber ring bonds to the pipe or you don’t pull the pipe up from the bottom of the lower collar enough, you loose expansion control, so when the pipe gets hot from the water discharge or the sun, the whole stack can move, ripping out the anchor points. This can also lead to downward pressure on clay drains at the bottom of the stack and easily breaking them or the snapping of branch pipes.
So in his instance I would fix a hopper head (please note, its now unusual to have waste pipes discharging into hopper heads, they where allowed at one time, but now, only I think if you are replacing like for like) And directly underneath it a collar clipped as an anchor point for 82mm, with an expansion gap for the hopper head.
I must admit you might have trouble getting a hopper head with a 82mm spigot; you may have to step it up in size or get a commercial/industrial hopper head. Ask your supplier what they can get.
Then using collar clips and barrel clips fix pipe.
Of course the proper way is to start installing from the bottom of the stack. So depending on what sort of draining system you are connecting too, use the appropriate adaptor and leave an expansion gap making sure you have a good anchor point to stop expansion pressure on the drain.
Then if required, fit an access point with another anchor point.
Then fix the rest of the stack.
The problem today seems to be, that not many people use collar clips and instead put barrel clips on. The result is, you often see soil stacks bent like bananas and out of shape all over the place.
You can work it out for yourself, if you think a barrel clip is a guide and a collar clip is an anchor. Try and work out where the pipe is mostly likely to expand and how you can control it, by getting it to expand into the collars, instead of pushing the pipe out of line.
Also PVC pipe in the sun can become brittle after a few years and will snap like a carrot if it has pressure put on it. I have seen houses where apparent uncontrolled expansion, on I think solvent welded stacks with out expansion joints, have snapped the WC bend going through the wall.
The PVC pipe may be a bit flexible but the fittings are moulded and usually brittle.
I may also say its advised to fix into the brick not the joints and use external screws with slot heads not posi or Phillips, with all the slots vertical so the rain runs out and does not help rust the head.
Good Fortune!!
