Dear Dave,
I have a reoccurring odor which I think is coming from the sink or gray water tank. What is the best way to clean and sanitize it? —Warren, 2010 Coachmen
Dear Warren,
There are two types of holding tanks in an RV: the black water tank holds sewage from the toilet, and the gray water tank holds water from the shower. The sinks inside an RV do not always go to the gray water tank. Rather, they go to the closest holding tank so the plumbing is easily routed to that tank.
What to do first
The first step would be to identify which tank your sink is routed to. It might be the black water holding tank and the smell is coming from that. If it is the black water tank, I would make sure to use the proper treatment, which is anaerobic with enzymes and reduces the sulfur or rotten egg smell.
Also make sure there is water in the “P” trap, as it can get sloshed around during travel and drain into the tank. Water in the “P” trap will create a barrier to keep smells from coming up to the sink.
Another source of bad smells can be from bacteria on the pipes and sink drain from rotten food. Bacteria breaks down food particles and will have an unpleasant odor, as well.
How to clean and sanitize tanks
You can clean and sanitize with bleach and water. A more environmentally friendly option is to use hydrogen peroxide, Dawn dish soap, and hot water.
Pour one cup of hydrogen peroxide down the drain and let it sit for a minute. This will release oxygen that will help break down the bacteria and other components.
Pour two teaspoons of Dawn dish soap down the drain and let it sit for several minutes—up to 10 minutes for really stinky smells. I typically use the scientific method of two “glug glugs” for measuring! 😉
Flush the drain with hot water from the faucet for one minute.
Most kitchen drain assemblies have the main basket with strainer installed from the top through the sink hole with a flange that is sealed with plumber’s putty. Some smaller sinks use a bathroom sink-type drain assembly like the one shown in the above photo. Both have a flange seated to the sink and will have a crease or gap between that flange and the sink material. Make sure you clean this out, as well, using a small brush or toothbrush to get rid of any food particles and bacteria.
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I’m diligent! Either using a spatula or paper towels and wipe down EVERYTHING before I wash it. I also have a screen in the drain, to catch stuff. We use lots of dawn detergent. If there is some leftover liquid like broth, boiled water…I put it down the toilet. Seven years now and no problems with smells.
There also may be an air admittance valve on the drain line. If it is stuck open, odors from the tank will escape. If it is stuck closed, the water may not drain fast enough to flush the ‘P’ trap completely.