I'm aware of most of the issues regarding floor drains in a garage/shop. My intent is to tie in my garage drain with my gray water line and dump both into an Infiltrator system separate from my primary septic system. I'm wondering if any one out there is familiar with the Watts OI oil interceptor units. Getting ready to do my slab rough in and would like to know if there are less expensive and/or equivalent units more suitable for a residential environment. The Watts Interceptor seems like a glorified drain sump with draw off provisions. It is required, listed, certified etc., but are there other options. 