Waste Pipe in Concrete Floor

[imroberts]

I'm in the process of refitting my downstairs bathroom.

The shower is being moved and I have already cut a channel in the floor for the new waste pipe.

The original waste pipe was buried directly in concrete in part, with the remainder just filled in with sharp sand to the level of the concrete. I'm wondering what is the correct thing to do with my new pipe. I know that outdoor waste pipes would be laid on and surrounded by pea gravel to allow for movement though obviously these are much larger pipes and my shower waste shouldn't be subject to any movement within the concrete floor (though I guess it could be subject to a small amount of expansion and contraction).

What is the correct thing to do? I obviously need to fill the hole with something relatively solid rather than simply leaving a void under the flooring, but not entirely sure what is most appropriate?

 

[denso13]

Pea gravel isn't to allow movement, partially fill with sand and finish with a screed over the top.

 

[ChrisJP]

If the waste pipe is plastic then it will by subject to quite significant expansion as hot water from the shower passes through it. So you do need to surround the pipe with sand to allow for this movement.

 

[imroberts]

THanks both. Is sharp sand appropriate?

 

[denso13]

Any kind of sand or fine aggregate, it isn't important.