Find out the proper process for getting your RV’s gray holding tanks clean. Doing so will reduce odors, keep waste flowing quickly out of the tanks, eliminate most major problems, and keep everyone in the RV happy.

We follow a lot of Facebook groups and pages for various RV owners groups, manufacturers, and general RVing interest. We do it mainly so that we can help answer questions RVers have about their waste systems and holding tanks (our article on tank additives is the one we’ve shared the most!). But we also follow along these discussions so that we can get ideas for articles, like this one.

On one Facebook page recently, an RV owner asked how they could get their gray tanks clean. It’s a common problem; there’s no onboard rinse or spray system on most RV’s gray tanks, so getting them truly clean can be a little frustrating. And since gray tanks can contain decaying food, human skin and hair, and other waste that isn’t truly “black,” they can smell as much (or more!) than your black tank. And that’s a pain to live with.

What’s going on in the gray tank?

We’ve cleaned over a thousand gray tanks in the years we’ve been in business. We expect black tanks to be smelly and gross, but we’ve also had some gray tanks where we needed to stand up, walk away, and get some fresh air.

Gray tanks harbor all kinds of waste in them: food particles from washing dishes; hair, skin, and other human waste from the shower and sinks; soap that “globs up” and becomes sticky, making little balls of waste that like to stay in the holding tank.

A lot of RVers also put enzymes, chemicals, and biologicals down their gray tanks, causing this solid waste to break down into a similar, sticky mushy substance, like we see often in black tanks that contain the same additives. Doing so can make gray tanks hard to get clean too.

Plus, many RVers leave their gray tank’s valve open, allowing liquid (and, granted, some solid waste) to seep out into the RV park’s sewage handling system. What happens, though, is a lot of solid waste is left behind, building up in the gray holding tank.

How to clean out your gray tanks

The process you take for cleaning out your RV’s gray water holding tanks is pretty similar to what you should be doing with your black tanks:

• Empty the tanks when they are 90% to 100% full (add water to raise the levels if you have to dump before this level is read on your tank sensors)
• Use a product like the Valterra Flush King Back Flush Valve to backfill your gray tanks and get them rinsed out
• Add in three to five gallons (depending on your holding tank capacity) when you’ve dumped and rinsed, and before using the holding tanks again (called “priming the system”)
• If you want to use a tank additive, we recommend adding 1/2 cup to one cup of our homemade tank additive to keep inside tank surfaces slippery and to reduce offensive odors

Moving forward.

Unfortunately, almost no RV manufacturer includes a rinsing system for the gray tanks, like all do for the black tank. This is a shame as it would really help to keep the gray tanks clean. There are afterwork tank rinsers you can add, however they can be difficult to add due to underbelly pans, tight spaces in bays and basement areas, and the need to tap into existing plumbing lines and set up a control panel or, at least, some sort of “on/off” switch.

Truly the only way to get your RV’s holding tanks — black and gray — “factory clean” is to have them hydrojetted out by a professional service like Kleen Tank. We have the equipment, expertise, and experience to quickly and thoroughly clean your RV’s holding tanks. Make an appointment today or ask us any questions you may have. We are always glad to help.

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