Waste pipe routing for ground floor bathroom to soil stack

tallac

My house is being renovated and the builder says there's a problem with routing the waste pipe for the ground floor shower. It is a concrete subfloor. He wants to put the shower tray 4" to 5" above the floor level to give him enough space for the waste pipe to have a gentle gradient downwards to join the soil stack outside. This would avoid him having to cut into the concrete as it would all be above the concrete level.

Picture of the soil stack outside:

However, this will look really ugly as I wanted a very flush looking floor. Even the shower tray I have is a very low profile one. I would like the shower tray to be as close to the floor level as possible by cutting into the concrete floor as necessary for the waste pipe.

However, the builder is saying that this is not possible because the plastic joint connection does not allow the waste pipe to join the soil stack any lower. He initially said that the plastic soil stack joint connection is connected to a clay soil pipe below ground and thus it would not allow him to have the waste pipe from the shower to go any lower. After some convincing, he is going to dig to see if the stack under the joint connection is plastic or clay. He said, if it is plastic, then it might be possible but if it is clay, then it will not be possible. In case it helps, the house is quite old (circa 1960 ish).

Highlighted plastic joint connection on the soil stack:

Highlighted shower waste pipe joining the soil stack:


I do feel the builder is wanting to take the easy option out, as there is a little bit of time pressure.
My question are:

1. Regardless of the material of the soil stack below ground level, is it possible to get the shower waste pipe any lower?
2. If the soil stack below ground level is clay, how can this be done?
3. What are the options here?
4. What are the likely costs for doing this work?

grumbler

What really matters is how deep the horizontal waste pipe lies that the vertical pipe is connected to. Everything else is irrelevant.

If it's deep enough (and, most likely it is) everything you want can be done, and IMO pretty easily.

The hardest part  is to cut/chisel the concrete slab. What's under the slab? Soil?

tallac

grumbler said:

What really matters is how deep the horizontal waste pipe lies that the vertical pipe is connected to. Everything else is irrelevant.

If it's deep enough (and, most likely it is) everything you want can be done, and IMO pretty easily.

The hardest part  is to cut/chisel the concrete slab. What's under the slab? Soil?

I believe it's soil although I'm not 100% sure. The horizontal waste pipe is around 115cm long.
My understanding of what the builder was saying is, that it wasn't possible to get the vertical joint connection any lower because it was probably attached to a clay pipe.

grumbler

tallac said:

grumbler said:

What really matters is how deep the horizontal waste pipe lies that the vertical pipe is connected to. Everything else is irrelevant.

If it's deep enough (and, most likely it is) everything you want can be done, and IMO pretty easily.

The hardest part  is to cut/chisel the concrete slab. What's under the slab? Soil?

I believe it's soil although I'm not 100% sure. The horizontal waste pipe is around 115cm long.

I meant the underground pipe - how deep it is

My understanding of what the builder was saying is, that it wasn't possible to get the vertical joint connection any lower because it was probably attached to a clay pipe.

If it's connected to a vertical clay pipe, you can extend  the plastic pipe, cut the clay pipe and move the connection deeper - up to the point where it's connected to the horizontal clay pipe.

Doozergirl

Everything is possible, put it that way!  

tallac

Thanks for the replies. Sounds like the builder is trying to avoid work. I'll shall insist that the shower tray needs to be flat on the floor.

koalakoala

I've just had this exact problem in a bathroom I've had redone. I ended up just getting the shower tray raised about 7cm. This is not what I wanted , and not what you want either, but I just wanted it finished as I've had work going on for months, and covid has dictated so many times what i can and can't have. 

tallac

koalakoala said:

I've just had this exact problem in a bathroom I've had redone. I ended up just getting the shower tray raised about 7cm. This is not what I wanted , and not what you want either, but I just wanted it finished as I've had work going on for months, and covid has dictated so many times what i can and can't have. 

Oh no, I totally understand that. My project has also been going on for months as well but I feel I have enough patience still to push back on this suggestion from the builder (not sure how long my patience will last though). If my builder is being stubborn about it, then I'll have to get another tradesman in just to do the bit of work that they're unwilling to do. It's ridiculous that this needs to be done like this as I'm sure the builders can do the job, they're just trying to cut corners.

greyteam1959

Dig down below the joint on the soil stack & see what's below that joint would be the first thing to do.
Then take it on from there