Today I sorted out an issue with a land drain that runs under my farmyard. In the recent cold spell we have had an increasingly large 'ice cap' growing in the yard - it got to the stage that visitors children in the holiday cottages were using it for rough skating.
I installed this perforated land drain quite some time ago when we had puddles forming. In the end it actually transpired that the water source was a leaking South East Water main in the road and it was running between layers to this point. The drain cured the problem but then they also repaired the leak!
When I started using my borehole as a source of cooling for my induction furnace it was convenient to draw water from the bore hole, pass it through a heat exchanger and return the slightly warmed water via this land drain some hundreds of feet away to a handy stream. As the bore hole was sightly artesian I arranged that the return pipe also served as an overflow. Now this bore hole was originally used for public water supply but that stopped when they decided that the iron content was too high - BTW it was originally 250 foot deep by 5 foot diameter in 1923 when dug - I've plumbed it to still be over 190 foot deep !
Now I'd always thought that the iron sludge that forms would perhaps block my pipes and I strongly suspected that to be why water was emerging from the course of this land drain and freezing into the ice cap - even several days after the weather has improved we still have a vestigial ice cap !
Now I was loathe to use normal drain rods on a perforated drain and instead wanted to high pressure water jet it with a retro-jet that should help to unblock the pipe perforations - I knew that I had one somewhere but not only could I not find it, I knew its pipe was only 25 foot long - OK Amazon what have you to offer?
Well £52 got me this delivered last night:
I had to cobble together bits from two pressure washers to end up with a trigger mechanism to start and stop the flow and be close enough to the action - but I got there in the end.
Now when I installed the original land drain I'd terminated it with a rodding eye at the high end so inserted the retro-jet at that point. Perhaps I should explain these things have six backwards facing jets to propel it forwards, and one forward facing to cut through blockages.
At about 15 foot in I come up against something solid - I couldn't get further. Measuring on the ground I was pretty sure that this was where the borehole overflow tee-'d in - blast do I have to dig! Well one last attempt got me though thank goodness to another (but softer) stoppage - working the high pressure hose in an out eventually I heard a fair old flow plummet into the stream. By the time I got to the exit end the flow had diminished considerably but there was a very large patch of very brown silty water going down stream.
At this point I wanted maximum flow down the pipe to flush as much out as possible, and of course a pressure washer doesn't create much flow. So I started up the Induction Furnace cooling system that has a flow rate of something like 50 gallons a minute IIRC. Sure enough more silty gunge and had the advantage of slightly reducing the borehole level.
In this image of the bore hole access manhole the green stripey pipe is the pump suction hose that goes down about 15-20 foot to a weighted strainer, and the 32mm MDPE pipe is the flow from the heat exchanger going into the branch in the land drain and thus out to the stream.
I left it flowing for some time before packing everything up. This is the retro-jet nozzle:
100 foot of high pressure pipe reeled for next time !
All together a satisfactory result only needing a brace of Ibuprofen and a hot shower to recover from !
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