Priming the system: An important step in keeping holding tanks working

Emptying and flushing your RV’s holding tanks are only part of the smart strategies to keep them healthy and working properly. There’s one more thing you can do to help the system.

Want to know a secret? There’s a way you can give your holding tanks a “head start” when you’re about to use them, something that will keep them draining faster, reduce odors, and, possibly, help sensors from misreading. You want to know, don’t you?

How holding tanks work

As we’ve said before, your holding tanks are not meant to be a septic system. That’s why we don’t recommend tank additives that contain harsh chemicals, enzymes, or biologicals, meant to break down waste. In fact, as we’ve noted in other articles, it’s those additives that are causing a lot of problems.

Your RV’s holding tanks are meant to be just that — tanks that hold waste until they’re full and you can release it into the park’s waste processing system (which likely then goes to a municipal waste processing plant). So keeping “stuff” from breaking down too much helps keep your tanks working properly.

So what’s the secret?

You know you should only empty your holding tanks when they are 90% to 100% full (adding water to bring the level up if you have to empty them before they reach that critical volume). Emptying your holding tanks when they are full takes advantage of the “tornadic effect” that occurs with full tanks.

Once you’ve emptied the tanks (and flushed them out, using either your in-tank spray system in your black tank or something like the Valterra Flush King Back Flush Valve (that can be used on both tanks!), it’s a good idea to “prime the system” before using your RV’s tanks again.

“Priming the system” simply means adding some clean, fresh water to your empty holding tank after you have emptied it. Why would you want to do this? As you know, holding tanks work best when there’s a high ratio of liquid to solid waste. Adding in three to five gallons (depending on your tank’s capacity) before you starting using them again is a wise move.

Jim Tome, Owner

Jim Tome, Owner

Hi, I'm Jim Tome and, along with my wife, Debbie, the owners of Kleen Tank LLC, the national leader in RV holding tank cleaning service. We've been RVers like you since 2004 and have traveled all over the U.S. in our Airstream travel trailer. We started the business about twelve years ago and have cleaned tens of thousands holding tanks in thousands of RVs. From tiny weekend travel trailers to monstrous fifth wheels to luxurious motorhomes, I've seen just about every situation there is with RV holding tanks and waste systems. I hope you enjoy our articles; I try to post at least one per week and we've got a great library of them to cover just about every problem. Enjoy!


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