It’s called underlayment and it’s to protect the liner from getting poked by small rocks and pebbles and causing a leak. Especially our area it’s so rocky, but sometimes we have to double up our underlayment or even use a thicker rock pad. If you surprised at the leak that can come from a hole the size of a pin needle.
Why do you put fabric behind the liner?
It’s called underlayment and it’s to protect the liner from getting poked by small rocks and pebbles and causing a leak. Especially our area it’s so rocky, but sometimes we have to double up our underlayment or even use a thicker rock pad. If you surprised at the leak that can come from a hole the size of a pin needle.