If I have to add a 2nd storage tank to hold and foward the waste in the wintertime, has anyone succeeded in putting two of those Auto-off valves in series, so that if either the pure water or the waste water tank fills, the RO unit will shut down? I don't want either tank spilling, and I can't run the 1/4" waste line outside in the winter (we do get cold winter nights in the Sonoran Desert).