I found out Friday that the local facility that services my 'Bus uses non-antifreeze treated fluids when draining the holding tank. Their strategy is to drain the holding tank on Saturday, then filling the toilet on Monday prior to departure, thus avoiding a solidly frozen toilet. This is a violation of UPS Ground Operations Manual policy which states that between winter months the fluid used for this will have a mix of anti-freeze. I can envision a lot of potential problems with this technique, foremost of which is the rendering inoperative of an aircraft system by a non-certificated person, with no MTX logbook entry. I could see where residual fluids in the recirculating system could freeze, rupture hoses and cause expensive damage to the toilet, as well as the avionics equipment located below. I am going to be the bad guy for a while until this gets straightened out.