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We are saddened to announce the passing of Gary Bunzer on April 17, 2020. We hope the RV Doctor website will continue to provide helpful information for you. Thank you for your interest and support for the RV Doctor - Debbie, Heather and Gretchen

Wednesday, December 8, 2010

Dumping RV Holding Tanks

I just completed reading your handout on holding tanks and odor control; very informative! My wife and I are new to the RVing world and we are excited about it but a little apprehensive at the same time. We have many questions, most we don't even know to ask yet! One question on the holding tanks, after reading your article, maybe I missed it, but if we only camp one or two weekends a month for a couple of days each time, do we still wait until the black and grey tanks are at least 3/4 full before we dump? That might mean that our coach would sit in storage maybe two to three weeks at a time with waste in the tanks. Is that okay? Another question on the fresh water tank, would I drain both this tank and the hot water heater after each weekend trip if the RV just sits there? Roger, (Topeka, KS) 

Roger, you should really avoid having that waste lying dormant in the tanks during the weeks between trips, especially in the solid waste tank. If you’re only using the RV on the weekends and it remains less than 3/4 full, simply add more fresh water so that the total capacity of the black holding tank is at least that full prior to evacuating. Dump each tank after every weekend trip. Here’s the reasoning; in order to maximize the flushing velocity, it’s necessary to have the tank filled or almost full. A partially filled black tank can develop tank blockages if there is not enough force to flush out all the contents. This isn’t normally a concern for the gray tank. Just simply evacuate it normally after emptying the black tank. And be sure to run fresh water down through the toilet after draining the tanks to rinse the sewer hose, the valves and the connections. 

The polyethylene water tank and the water heater will not suffer any ill affects during storage periods of less than month if you choose to leave them full of water. But you be the judge; if the water smells odd or tastes stale, then you may have to drain and refill after each use. As you are probably aware, it all depends on the quality of the water you put in there to begin with, right? Many motorhome owners prefer to dump all the tanks, including the fresh water to avoid the added weight while driving.

By the way, the December 2010 and January 2011 issues of Family Motor Coaching Magazine feature an in-depth, two-part article on Waste Management. Be sure to check them out! I go into great detail in all areas of waste containment, odor control and preventive maintenance, including information regarding new products and processes.


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