Some plumbing guidance please

[robgraham]

I'd done a lot of house plumbing up to about 30 years ago in my cottage's r enovation but little since.

I now need to run a water supply to a polytunnel, which effectively is on t he wrong side of the long narrow building from the water supply. I've look ed at various options and consider that tapping off the header tank feed in the attic is the easiest as the supply can be easily accessed for isolatio n and requires only plumbing and no drilling through 3 ft walls, crawling i nto to difficult places, etc.

The feed will go over the wall head and down the outside wall in a larch co ver to a garden tap and then in blue pipe underground to the polytunnel.

I'm not familiar with plastic piping, but I see Screwfix say that polybutyl ene pipe is more suitable for situations requiring more flexible pipe, and it seems to me that as the system will be drained down in the winter, I cou ld use this for the 6 metres in the attic and then the 3 metres down the wa ll to the tap before changing to the underground pipe.

Does anyone see any problems with this ?

Thanks Rob

[harryagain]

I now need to run a water supply to a polytunnel, which effectively is on the wrong side of the long narrow building from the water supply. I've looked at various options and consider that tapping off the header tank feed in the attic is the easiest as the supply can be easily accessed for isolation and requires only plumbing and no drilling through 3 ft walls, crawling into to difficult places, etc.

The feed will go over the wall head and down the outside wall in a larch cover to a garden tap and then in blue pipe underground to the polytunnel.

I'm not familiar with plastic piping, but I see Screwfix say that polybutylene pipe is more suitable for situations requiring more flexible pipe, and it seems to me that as the system will be drained down in the winter, I could use this for the 6 metres in the attic and then the 3 metres down the wall to the tap before changing to the underground pipe.

Does anyone see any problems with this ?

The pressure will be very low so don't expect more than a trickle. Also some plastics are affected by sunlight.

[Tim Lamb]

In message , harryagain writes

I was going to criticise the limited pressure but spotted the take off is from the *feed*:-)

[dom]

Provided you don't try and cut plastic pipe with a hacksaw, or chew through it with your teeth - it's delight to use. Buy a proper plastic pipe cutter, buy the pipe end inserts, buy straight rather than coiled pipe - and you'll have no problems.

[Roger Mills]

Agreed (almost). Straight pipe only comes in short lengths which would have to be joined. If you use coiled pipe, you can do it in one length - which is better. In places where it shows, you can get it to look passibly straight and tidy if you clip it to something solid every couple of feet or so.

[sm_jamieson]

I was envisaging a 25m metre long straight piece of pipe on the roof rack ! If you can run hot water through the coiled pipe it helps straighten it out a bit. Simon.

[robgraham]

's renovation but little since.

gh it with your teeth - it's delight to use. Buy a proper plastic pipe cutt er, buy the pipe end inserts, buy straight rather than coiled pipe - and yo u'll have no problems.>

Thanks guys for your assistance. Let's see if my thinking is workable for this garden water supply problem.

The difficulty is that the cottage is 20m long and there's no easy route fo r mains water for the north side garden. I'm working on tapping off from t he mains feed to the header tank in the attic and running the pipe over the wall head and down the wall to a tap and on underground to a polytunnel. The walls are 3 foot thick stone and I've located a suitable narrow passage way over the wall and under the gutter.

My first problem is how to pipe this as the pipe may well have to wriggle a bit at the wall head and then turn 90 degs. to go down the wall. And of c ourse access to the wall head is constrained by the roof! The pipe will be boxed in once outside so UV won't be a problem. Anybody got any suggestion s on this ?

Now the second question is could I use motorised valves at mains pressure a s it would make life easier if I could isolate and drain down this pipe wit h just the flick of a switch ? Or even automatically if the temperature go t near to freezing.

Thanks for any input Rob

[Tim Watts]

I'd use blue MDPE - whilst it's supposed to be buried, it's actually pretty resilient even in sunlight. Much tougher than PEX or PB white pipe (aka JG Speedfit)

MDPE will probably survive freezing - though the joints may not.

I don't see why not - the valves in those are 1/4 turn valves so, unless it actually leaks under pressure, I don't see what the problem could be.

You can get designed-for-mains electric water isolators though - might be worth a google? "Surestop" (sp?) rings a bell...

[dom]

6m straight lengths are available, but agreed - no joins is better. Coiled 22mm pipe can be a beast though.

[Rick Hughes]

Why not use barrier hep20 or similar throughout the run, you will need to cover the pipe on outside wall for UV & frost protection .... plenty of neat ways to do that. Use same pipe underground just run it inside an something for physical protection ... I have used standard rain water downpipe, local BM always have old discoloured stuff you can have for free.

You could of course change to a proper 25mm underground MDPE pipe .... cheap enough if you buy it buy the roll.

[robgraham]

's renovation but little since.

on the wrong side of the long narrow building from the water supply. I've looked at various options and consider that tapping off the header tank fee d in the attic is the easiest as the supply can be easily accessed for isol ation and requires only plumbing and no drilling through 3 ft walls, crawli ng into to difficult places, etc.

h cover to a garden tap and then in blue pipe underground to the polytunnel .

utylene pipe is more suitable for situations requiring more flexible pipe, and it seems to me that as the system will be drained down in the winter, I could use this for the 6 metres in the attic and then the 3 metres down th e wall to the tap before changing to the underground pipe.

Thanks all - my problem is wiggling the pipe over the wall head and under t he gutter. There's a hole at the required point, but the path isn't that s traight.

While hunting in the plumbing bits box this afternoon for a 10mm pipe cutte r, I came across some flexible pipes for taps - ahh, that's the solution; t he pipe system should be drained down in winter, but if not that inside won 't freeze, the outside can break if the worst does come to the worst withou t anything suffering; however the wall head bit is a worry, but a flexible pipe should tolerate freezing.

Rob