Why not just regular PVC?
I think regular PVC would be something of a compromise and would make the plumbing look like a nuclear power plant. For one, the overflow box is external, so to get it into the sump in the stand with regular PVC we'd have to do two 90 degree turns to get into the stand: down from the overflow, sideways into the stand, down again into the sump to avoid splashing. Flexible PVC wouldn't need any since you can just bend it a bit right into the stand.



