Timothy Murphy
wibbled on Sunday 25 October 2009 12:33

I have a very long (15m), almost horizontal, external waste-pipe
used to drain a washing machine in a utility-room.
The flow down this pipe does not seem as fast as it used to be.
I'm wondering what the best method is to clear the pipe?


If the pipe were gunked with fatty residue I might run some warm caustic
soda down it - even better, block teh outlet, fill the pipe and leave
overnight.

In the case of a washing machine, I suspect the gunk is more alkaline in
nature. Assuming the pipe is copper or plastic, perhaps a similar approach
with diluted brick acid (HCl) - perhaps a final dilution of 5% HCl to water
(that's 1:4 or 1:6 brick acid to water depending on original being 20% or
30%); that's not *particularly* dangerous (mind your eyes though).

Again, block the pipe if you can, fill and leave.

--
Tim Watts

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