Tree root in trench

Its never a good idea,. It will survive but you may get some visible damage to the tree in that area: It will weaken it to blowing over, and there is a possibility that you will provide a nice area for fungal attack.

But it sounds like you haven't much choice. Cross your legs and pray...;-)

Or perhaps slide the pipe UNDER that root?

In all cases use PLENTY of gravel packing round it near the tree.

I do not think that one 25 mm root 75mm below the ground will have much effect on the stability or health of the tree. It is when a deeper and bigger buttress root is cut that serious problems occur

I have in the past cut through some these near surface roots to prevent damage to the surrounding lawn,and to the kid playing on the lawn as the roots were at the surface in some places. This was several feeder roots on each tree. The work was done on the advice of a landscape gardening company. The trees were 15 year old cherry and there was no discernable effect on them

Tony

Indeed. I did some stuff like this near an apple tree, and it seriously affected it. Got many more apples the next year.

(then it went back to normal) (google 'root pruning' )

Hmm - I'd rather not have that as the damn trees produces more than enough apples at the moment. Ha, well that's life ! As others have said, being a surface root and quite small in diameter in comparison to the main ones, it shouldn't make much difference.

Thanks for all the replies

Rob

Why bother cutting? Your drain will surely be well below it. Just dig the trench and thread your pipe underneath. Minimal damage to tree, no route for infection for example.