Question: What can be done to eliminate odors from holding tanks? I've tried most of the commercial additives, and they seem only to mask the odor for a while. Can bleach or ammonia be used? Also, can I leave the valves open since I'm connected to a sewer?

Answer: Rather than masking odors from the holding tanks, I recommend using a biological additive, one that employs live bacteria to eliminate the odor causing molecules. Many suppliers offer an enzyme-based additive. Avoid using any chemical in the tanks, especially those that contain formaldehyde. Detergents and some ammonia products might damage seals in teh termination valves.

Contrary to what I have recommended in the past, also avoid home brews. Why risk the integrity of the RV waste system to save a few dollars? Once you switch over to the live bugs, however, remember that use of other types of deodorants and/or detergents will kill the good bacteria and defeat your efforts.

As for evacuating the tanks, many RV'ers completely close the black water tank and evacuate when it approaches full capacity. Leave the gray water valve fully open so bath and kitchen water freely drains. The drawback to that method is that foul odors can and will proliferate and emanate from the gray water tank also and do so quite rapidly.

I support the method of keeping both container valves full closed, evacuating each when almost full and using the live bacteria additive in each tank. That will help eliminate erratic monitor panel readings from the gray tank.

To address the issue of having to trudge outside to open the gray tank valve quite often, or in the rain, I recommend a product called the Drain Master, which is producted by PhaseFour Industries (www.drainmaster.com).

Drain Master is an electrically operated termination valve. Powered by 12 volts DC, the Drain Master can be adapted to any hlding tank and operated with the simple activation of a switch mounted at or near the monitor panel inside the RV.

Installed on each tank, the Drain Master eliminates having to attend to the termination assemblies, except to perform the initial hookup.