What size pipe to use for garden tap - long distance 80m? Overground not buried

Anakin · Jun 21, 2017

Two things. Customer has a huge garden, requiring a tap at the end. Firstly is it best to use say 25mm bore plastic pipe? Will I get better pressure by using a larger bore pipe, or lose pressure over that distance? Direct off mains.
Secondly the customer does not want their garden dug up to put this pipe in a trench, and is mostly unseen next to a hedge. The blue pipe is meant to be buried to protect from UV, and it would cost a small fortune to lag that much pipe. Pipe will be shut off and drained in winter, so is there a particular overground exposed pipe I could use without lagging? Or is the sunlight damage thing just scare mongering and will be fine to use?

kozak1968 · Jun 21, 2017

They make black poly for above ground. As for diameter it would also depend on pressure and flow rate.

Old Account · Jun 21, 2017

You would also have to dig up the trench about 750-1350mm so it's not as easy either. Apparently you do not need to lag the pipe in ground if you lay it between 750-1350 but me personally I would always do it. You could install it n a duct or lag it as you already have mentioned. But as above you can get black mdpe pipe

ShaunCorbs · Jun 21, 2017

whats the pipe going to be used for?

Stanios · Jun 22, 2017

If I was the cust I'd just get standard garden hose 100m and attach it to existing tap.

zzzjim · Jun 22, 2017

Is the garden on a gradient ?
( or pretty flat)
.. Do they have a pet that likes chewing hosepipe..

chris watkins · Jun 25, 2017

Are you a Plumber Anakin?
Do you hold your Water Regulation ticket ?

Anakin · Jun 25, 2017

I am a plumber yes lol. I wouldn't normally involve myself in jobs involving pipes underground.
At the moment they do use a really long hose pipe, but don't want to walk the distance to the first tap to turn it on and off, and clearly they can't have the mains fed all the time through the hose, i.e leave the first tap on if a new one put on the end..
It's just a water supply for some veg gardens at the back. I just hope the double check valve, doesn't restrict the pressure too much, or jam up like they can do.
Black mdpe pipe it is, I'll go for 25mm.

Ric2013 · Sep 4, 2017

Just make sure that double check valve is at the source so the water, stagnant in the pipe, can't backfeed the mains when it warms up from sunlight. And they jam because they freeze - the double check valve should be indoors. How about a mini-expansion vessel to allow for expansion or is MDPE forgiving enough? Whether or not you're a plumber, let's just hope you do it right! I don't know what's right - I'd be asking the same questions as you...