Trenching for water pipe

27 Dec 2008
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United Kingdom
I'm going to be replacing my lead water supply in the next week or two. I've been told to dig the trench 2'6'' and come up through the floorboards at the front of the house.

I've found out since the plumbing contractors left that the foundations aren't as deep as that. They are only a few rows of bricks below the ground level. Is it ok to trench under them wide enough to fit the 100mm ducting for the mdpe pipe?
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Well you could and it would probably be ok, but depends on how good the brickwork is, what the ground is like, how wide your trench ends up as, yadayada.

If you want a pukka job, then dig down 450 below footing level or 150 below the level of your new water pipe, whichever is the deeper, for 450 or so along footing, then dig under to back face of bricks forming the foundation. Clean down the underside of the existing footing. Place a 38mm pipe as a sleeve to the water pipe at the required level. Push it into the soil at the back; make a ply shutter across the front of the excavation, 150 out from the outer face of corbelled brick footing. Fill the excavation behind the shutter with 1:2:4 concrete. Cast this up to 75mm from underside of existing footing, wait until following day then ram 1:3 cement/sand mix with water just enough to bind it together into the gap; bang some slate in to make sure that it's tight.

Then again, you could just resin-bond some helibar into the bed joints every 150 for two or three bed joints, starting at the top of the corbelling, extending 450 past the trench, and then repoint, doing this on both sides of the wall.

The choice, as they say, is yours...
Thanks Shytalkz. Where the supply will be coming up into the house is in the corner of a small alcove about 700mm wide and long to the side of the entrance porch (1930's semi).

The ground is heavy with clay and the surrounding area outside (gravelled) takes some time to drain rain water away.

Your pukka job sounds good, but if this should involve anything more than digging a narrow (needs to fit just the 100mm ducting) trench, then I may just do the trench in across the garden and leave the point of entry to the "pros".

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