Thanks to the Love forum for a lot of trolling for solutions. My question - I bought an 1920's upgraded farmhouse with grey water system, which I assumed was unvented . On closer inspection, it turns out the septic (serves one toilet only) is unvented. The 1.6 gpf head works fine, and no odors. Should I be concerned about the lack of a vent pipe? The house roof is steel, with a steep pitch - and I'd prefer not to if I don't have to. The pipe has all been replaced with pvc, so that part would easier. Thanks Gary