posted 7 years ago
OK, well the original question was about pipes with a 4" diameter. I don't think you can create a useful riser shoving a fibre blanket into such a small pipe.
When you said the blanket protected the pipe, that sounded like the blanket would be on the inside, but I don't think there's room in a 4" pipe. This is why I asked my question.
Having the blanket on the inside would require a pretty good sized clay pipe, maybe twice that size? Like, 8" across on the inside.