Geotextile Filter for French drain woven or non-woven?
It depends on what your soil consists of. Actually, a nonwoven fabric is recommended for soils on the sandy side. However if your soil is a good part (>20%) clay, thats where things get tricky. The opening has to be smaller, about 70 US Sieve (.212mm), but there's a catch. The smaller opening will now be subject to clogging the fabric instead of the pipe and then the entire trench ends up rejecting the water. I'm currently reading about woven monofilament fabrics but the only viable option appears to be a Carthage Mills 20% Fabric. It's got a 70 US Sieve opening, 20% Open Area, 48 g/pm flow rate (may be an issue as it's half of what is common for nonwoven), and a permittivity of .68 sec which should be closer to 1.0 or greater.