Drain pipes problem

MarcusMaximus

I am doing a bathroom refit where I will be replacing the old bath with a shower. I have to install the shower tray over existing piping which consists of the sink drain pipe and the hot and cold copper feeds. The problem is both drain pipes are too high so I need to accommodate that somehow. I want to have both, especially the 6' long sink one, as low and as close to the floor as possible while allowing for 1.5 inches of slope for the long one. The shower tray will be raised about 90mm above the floor. So I will be left with both drain pipes going up at some point to join the pipes that exit the wall, which is no doubt incorrect. Is there any way to arrange this without having to move the exit pipes lower as I really don't want to start hacking out the external wall?! Can drain pipes go upwards at all for a short section?

Some pics:

Of course I'll also have to move those two small pipes that go downstairs lower as well as re-arrange the large bath pipes so that they feed the shower.

Obviously I'm fairly new to this although I did do all the plumbing for the kitchen some years ago as well as for a camper conversion so not a total newbie!

MarcusMaximus

Here is where those pipes exit the wall. If I have to drop them I'd also need to relocate them in the stack, as well as lower that junction that receives the soil pipe. Definitely beyond my skills so I hope there is a way around this..

Magilla Gorilla

Tie the higher sink drain pipe into the lower drain pipe internally? It’s all going to the same place anyway. Not a plumber!

MarcusMaximus

Even the lower pipe is too high as afaik it would need to slope downwards by 1/4 of an inch per foot = 1.5 inches over its 6ft length. Which means the shower tray would be way too high off the ground (even though the risers I will be using can actually go higher), which would look ridiculous.

So in order to have it at a reasonable height, those two waste pipes would need to be angled down towards the floor while still inside the wall cavity as the tray will go right up against the wall. However you might be onto something to just use the lower pipe - I could easily feed the drain pipe from the shower into it instead of the higher one, if it would work to have both the sink and shower drain into the same pipe. It is a bit smaller than the top one, not sure what difference that would make.

I’d still be left with the tray being too high though, unless I do away with that slope altogether..

MarcusMaximus

How about a small upflush system or a pump to push the waste water up into the existing drain pipes? Full-on macerators or shower waste pumps would seem overkill for this application as we’re only talking about 6-8 inches of a climb. Any good? Available?