We have a working Thermasn and it is great. If we are traveling about 3 hours of running will take the black tank from full to a bit under 1/2. (1/2 is as low as the Thermasan can take it.) If we are parked it is necessary to dump every other day. When traveling the limiting factor is the fresh water tank which will last for 5 or 6 days. If you have one installed but not functional they can be repaired/refurbished to operational condition. It should also be possible to recreate one from scratch.