UKC

So, we're having a window put into the downstairs toilet, which backs onto the outside wall.

Having got the toilet out for work to commence, it seems that the pipework for filling the cistern comes down the wall from the ceiling pretty much exactly through the middle of where the window will be. I had hoped that when the house was built, they would have routed the pipe through the boxing in for the soil stack that is right next to it, but no.

Easiest would seem to be cutting the pipe top and bottom of the window and route around the window with copper pipe (there isn't enough space behind the plasterboard to use plastic - the joints are too bulky compared to solder elbows). This will involve lots of fannying around because where they've put the dot and dab behind the plasterboard is coincidentally down where the sides of the windows are.

Once that's done, though, the whole lot will be tiled over, so initial mess won't be an issue.

Can anyone see any issues with doing this - I can't think of any.

The answer is not "put the window somewhere else", or even "don't put the window in"

I can't think of an issue with doing that.  Convention is just generally to run vertically or horizontally and not diagonally, so people can find it easily in future.

As an alternative, is it easier to lift the floorboards to reach it from above and use plastic pushfit to divert it down the soil stack conduit, abandoning the bit that is in the way?

Maybe think creatively. Is there an alternative water source to get to the cistern? Maybe from a kitchen or a boiler feed nearby? 

Otherwise, if space is tight you could try copper push fit, they are much smaller than plastic push fit. I'm not supper keen on push fit because I'm a luddite and like the security of a soldered joint but, if they don't leak when they are first put together and they are clipped in properly so they should be fine for a lifetime.

The only two issues I have heard of with plastic are

Is the copper pipe being used as an electric earth? If so you may need to maintain the circuit.

Mice eating the plastic pipe.

Otherwise plumbing with plastic can take a fraction of the time of using copper.

I admit I didn't think of that, but the bathroom above has a tiled floor and would be a nightmare to do that, quite apart from the bath being in the front of the soil stack - which is also tiled in that room.

I also wouldn't be surprised if the pipe running through the floor has a "T" end that goes both down to this room and up to the toilet above.

I'll admit it is also very much cheaper and less likely to get stolen for scrap. If it's a long unbroken hidden run then plastic is a no brainer, It's just that the joints are so fat and ugly that you don't really want to use them where they are visible.

Not really - it's a bit isolated and trying to run anything from the cold tap on the sink in the room would involve hacking out quite a lot of wall and would have to be routed around radiator pipes.

I've never used them and a quick look on Screwfix suggests they need special tools, so I think I'll stick with solder joints, especially as there's probably a pile of them in my Dad's garage.

The push fit fittings only require special tools if you need to undo them, otherwise you just make sure the cuts are clean and well de-burred and push them together.

If you have space to get in and solder then that's obviously the cheapest option, I was just thinking that if you need to make a joint in an inaccessible location they can be useful.

Depends which ones.  There are two main systems - Hep2O and Speedfit.  The former require a tool to release them, the latter don't, and have the extra security of a screw-in collar which prevents them being released accidentally, so I prefer these.  They are however a bit bigger.

I have a feeling both are now by the same company (Wavin).

Edit: ah, sorry, missed that you were talking about copper pushfit.  These I believe are the same as the Hep2O system and are a similar sort of size.  There is also a third system available in copper - pressfit, which sounds like pushfit but requires a crimp style tool to make the fit, which is then irreversible - I think the OP might be thinking of those?

FWIW you can use plastic pushfit joints on copper pipe (it's designed this way so you can join it to existing copper systems; the other option of using compression joints with plastic pipe I believe doesn't have quite as good a record of not popping off randomly) though that doesn't deal with the OP's space issue.

Could you make a hole in the downstairs toilet ceiling and access the pipework through that? OK, it’s still a mess but repairing the ceiling and getting it replastered shouldn’t be too expensive.

Hep2O is owned by Wavin, which is owned by Orbia. SpeedFit is owned by John Guest, which is owned by Reliance. But we're quite off topic now! :-P

Yes, I got confused with pushfit and pressfit - the press fit would be prefereable space-wise, but are expensive and it's going to be a pain to cleanly cut the pipe ends, so I think solder will be the best option.

I think it's probably fair to say that if you have the time and the skills, solder is always the best option.  However you can save a lot of time using pushfit and it is like Lego, though you do need to be picky about the quality of the cuts, as botching or rushing them can lead to later failure if they damage the sealing O-ring or if they mean the grip is sub-optimal, and if you do a crap job you can't just sand it to a better one like you can copper.

Urinal on top of the cistern, gives a reduction in water consumption and no need to replumb.

The OP can thank me later.

Can you get a new feed under the floor boards downstairs and just remove the existing one.

Doesn't work with concrete floors mind.

Yep - there's the problem with that, right there

Not always - plastic might be preferable to avoid hidden/awkward/less joints, or in a loft (fire risk).  

Not necessarily.. depending on floor you can often chase a channel in a solid floor for a 15mm water pipe,  if copper make sure it's fully denso wrapped or the alkali of cement rots it. A builder or plumber can advise

If the bath is in front of the soil stack is it possible to access the soil stack from underneath the bath?

Never used push fit but if your pipe work is old half inch  then push fit may not be good. 15mm Yorkshire fittings will solder ok though.

Theoretically, but it would still be a lot more faff than just routing around the window.

New build house (~3 years old) so will be 15mm standard.