Help with pumping grey water into existing waste pipes

[mactabby]

Hi - my wife has got herself an empty retail unit for her cake business and is expecting me to fit the kitchen for her. The previous tenants had a high-level sink, because the waste pipe leaves the unit about a metre up the back wall, but she wants her kitchen at normal height. One option is to put in a floating floor and raise everything up so the whole work area is at a height dictated by the sink waste. We're not keen on that because of cost and time, although I haven't ruled it out.

The other option is a pump under the sink to lift the waste water up and out of the existing waste pipe. I'm familiar with macerating pumps and their problems, but it's a downstairs unit on a concrete floor and would have only grey water to deal with, and as it's not handling toilet waste I don't mind cleaning it out from time to time. However, I don't have control of the waste pipework after it leaves her unit. It turns three or four 90 degree bends before joining a waste pipe in a cafe nearby, all using compression joints on 32mm pipe, and I'm concerned that a pump might cause problems further down the line - eg burst joints, fountains out of the neighbour's sink, etc?

So two questions I hope someone can help me with:

1. Is pumping feasible at all given I'm connecting to existing internal pipework? Any suggestions for how to improve the situation?

2. As it's grey water, is a macerator necessary or is there a simpler pump solution? Any recommendations?

Many thanks in advance
Mac

 

[JohnD]

drill a new hole in the wall.

 

[Blagard]

However, I don't have control of the waste pipework after it leaves her unit. It turns three or four 90 degree bends before joining a waste pipe in a cafe nearby, all using compression joints on 32mm pipe,

I appreciate this may be why you have not listed a new hole through the wall, but to be honest that would usually be the most sensible answer even if it means getting a new lower boss connection on the stack it goes to. So I would suggest you have a chat with the whoever you share a stack with.

You should use a 40mm waste for a sink because that 32mm is really too small

 

[Agile]

There are versions of the macerators for sink waste. They are no problem.

Because they pump hard then can cause compression joints to come apart so you are only expected to use solvent welded joints. If that's only outside then perhaps it would not be a big problem and so you could take the risk.

But as said waste pipes from a sink should be in 40 mm. At that size the pump would probably be OK with compression joints.

Tony

 

[Tipper]

Is there not another drain you could tap into?
Surely there is a wc in the retail unit?

 

[mactabby]

Thanks for your comments everyone.

Is there not another drain you could tap into?
Surely there is a wc in the retail unit?

Unfortunately not. The unit is in the centre of an old mill. The cafe whose pipework our waste joins also lacks an exterior wall, so at the moment we don't even know where the stack is! Drilling a new hole would shorten the run but not solve the problem.

We've asked a plumber to investigate where the stack is for us and quote for running new solvent weld pipework to it if possible (ie in parallel to the cafe's pipework). I'd do it myself, but as it will involve sticking new pipes through someone else's cafe I thought it'd be better done by a pro.

The other option we're now looking at is putting in a vented tank above the old waste, pumping into that (perhaps using a grey waste pump like they use on boats rather than a Sanivite - about a third the price!) and letting it drain naturally into the old waste. I'd box it in and it would need cleaning regularly but it seems like it might be a viable cheaper option.

Thoughts?