PVC inside walls sludge build up?

[Skimmerking]

this is what i did. but its funny but it worked.
on my 3md the pressure pump i put some heavy duty kim towel at the top of the return pipe where the return pump is .i did it due the union valve.

Thne i put on the pump and it blew the crap out of the sludge, But rember have somthing ther to catch it like a net in the water.

it worked for me thou.

mike

Or you can take a weight that would fit in the pipe and tie it to the rope and drop it down and then put it through