[bigginge]

Our allotment is ideal apart from one thing - it's so far from the nearest water trough. The association say they've no money to put in new ones so my neighbouring plot holders have agreed to put a few pounds each to get one off of ebay. We've found the mains water pipe which runs round the side of the plot and decided where to put the trough central to the plots, which is about 20 metres from the supply. The question is - how deep should the pipe to the trough be buried to avoid burst pipes in winter?

[Yorkie]

The water pipe on our site is at least 12" deep, probably more than 18" (we haven't actually got down to it yet  )

One different consideration is what your water pressure is like at present.  If you take more spurs off the main pipe, you run the risk of decreasing the pressure so that everyone suffers.

[mumofstig]

Our site turns the water off every winter so that the pipes can't freeze. Then it's not so much of a worry

[bigginge]

Thanks for the replies. There are about 200 plots on our site so I don't think one more trough will make a lot of difference to the water pressure. A few years ago they were going to sell a load of land off to the school next door. It eventually fell through but by that time the water troughs had been removed. My neighbouring plot holder was clearing a space for his shed a few weeks back and found a capped pipe; when he removed the cap water shot out. So we plan to run a pipe from there to the trough.  I suppose we could put a stop cock there to turn it off during the winter. 12"-18" wouldn't be too bad to dig down to, I was worried it might need to be twice as deep.
Will need to check it's OK with the association but I think we'll go ahead with this - thanks for the help.

[Slowgrind]

I think that you may find that the water supply company will require any water pipe to be 750mm below ground level to prevent freezing! It's  no simple task installing a new water main.

[Weston grower]

I agree with Slowgrind. 750mm deep is the minimum. Anything less will almost certainly lead to a burst in a bad winter.

Sorry, WG

[TerryB]

I would think the need to have a water pipe at 750mm is more to do with ground disturbance than freezing. It would have to be a really bad winter, alot worse than last year, for the ground to freeze down to 450mm (18").
 
Just make sure it is well insulated as it comes to the surface.

What depth was the capped pipe?
Assume this had not frozen.