RV Holding Tank Tips

It’s a dirty RV job, but someone has to do it! Grey water and black water holding tanks. The basics are simple – store your waste water in tanks and, when the tanks get full, empty them. There are, however, tips that RV’ers have stumbled on and passed on. Many of them are hear for you read before your next motorhome, travel trailer, fifth wheel, or camper trip.

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  • First tip: the one you always hear first anytime you read about RV holding tanks – but you always hear it first because it’s that important. DO drain the black tank first and then the gray. The reason is simple – get the solids and nasties out first, and then “rinse” with the soapy, less nasty water.
  • Don’t dump or rinse food particles into your grey water tank.

  • If it’s your first time out with a new RV and the black water and gray water valves are not labelled, the black tank valve is usually bigger than the grey.
  • If your tanks have a built-in flush / rinse system, use it every time you empty your holding tanks. A little bit of preventative maintenance goes a long way.
  • After you’ve drained your black tank, it helps to pre-load it with a gallon or two of water. The water will keep the bottom of your tank slippery and start to break down solids more quickly.

RV black water tank chemicals?

  • The RV world is divided on whether or not chemicals should be used in black water tanks. If you are noticing a lot of odor from your holding tank, make sure you’re flushing it completely when draining it, and check to make sure your holding tank vent is clear.
  • Another tip to avoid odors from your RV’s black water holding tank is to never run the bathroom’s exhaust fan while flushing. The exhaust fan creates negative pressure and when the toilet flap is open, it can create a rush of air from the vent, over the contents of the black tank, and out the toilet bottom to your RV.
  • If your RV toilet bowl is not holding water and you’re getting whiffs of unpleasantness from the black water holding tank, the seal on the flap at the bottom of the bowl may need lubricating with a special lubricant, or replacing. Both are simple tasks.
  • If you do choose to use an additive in your RV’s holding tank, use an enzyme-based treatment. Never use a formaldehyde-based treatment as it can cause damage to sewer systems and dump stations.
  • Never use a caustic drain cleaner in your RV plumbing system. It simply makes your plumbing chores far more dangerous.
  • If you’re in an RV park, never leave your black water valve open. Doing so allows the liquid to drain out and the solids to build a hard-to-dissolve pile often referred to as the poop pyramid. You can, if you choose, leave your grey tank valve open at campgrounds but remember, you will want a good amount of gray water to flush your drain hose after emptying your black tank.
  • Always wait until the black water tank is at least two-thirds full before dumping it. You will need this much volume to make sure the liquid portion moves fast enough and long enough to remove the solids. If you’re near the end of a trip or season and your black water tank is less than two-thirds full, add fresh water before dumping.
  • Don’t look for the cheapest RV sewer hose. It won’t be such a good deal when you’re cleaning feces from the ground. Buy a heavy-duty hose.
  • Consider buying a 10-foot sewer hose and a 20-foot sewer hose. That will give you convenient hooks to a variety of distances.
  • Carry a separate hose for any holding tank work, including hooking up to a tank flush system, and always keep it in a separate location from your freshwater hose.
  • Treat RV dump stations with respect – especially free ones that you encounter. More and more dump sites are closing – largely because it is becoming an inconvenience for the owners to maintain them after being used by careless RV owners. Never put anything other than the contents of your holding tank into a dump station and always leave it as clean as, or cleaner than, you found it.
  • It may sound gross, but you should use a clear adapter between your holding tank valve and the sewer hose. It’s really the only way you can tell if you’ve thoroughly drained and flushed your black water tank.
  • You don’t have to use special RV toilet paper, but you DO need to use toilet paper that breaks down easily. You can perform a simple test by placing a couple of squares of toiler paper in a container with some water… give it a couple of small, quick shakes to simulate flushing… and then check to see if it’s started breaking up.
  • Never place wet wipes in your RV toilet. Even the ones that say flushable. They are flushable, but they don’t break down. I’ve seen them put in a mixing bowl with water and mixed for 5 minutes without breaking apart.
  • Some RV owners say that dumping ice cubes into an empty or near empty holding tank will help break up solids as you drive. One guy has tested it with a clear test tank and a drive around town with some “artificial solids”. The results were disappointing.
  • Grease and residue can build up in the gray tank and cause odors or, in a worst case scenario, affect your valves
  • Before heading into a state or province you haven’t visited, find out what the RV sewage regulations are to avoid surprises. For example, finding out your sewage drain hose isn’t allowed to touch the ground, and you don’t have a support.
  • Rinse the outside of your sewer hose before storing it. Small bits of sand or gravel can cause punctures when it’s compressed for storage.