RV Grey Water Tank – The Ultimate Guide: Read This First

Published on September 17th, 2019

What is a Grey Water Tank On an RV?

An RV grey water tank holds all your grey water.

Helpful, right?

Let’s back up a little. Grey water is all the water that has been used in your RV, except what is used to flush the toilet (that’s called black water). All the water you use for showering, cooking, washing dishes, and everything else goes into your grey water RV tank. Black and grey water tanks both drain into the same outlet, but they have different valves. You should keep the grey water tank valve closed and allow the tank to fill ¾ full before you dump it. You should also add a grey water tank treatment chemical or your tank will smell.

Your grey water serves another important purpose – it rinses out your sewer hose when you dump your black water.

How to Drain a Grey Water Tank

When your grey water tanks for RV are full, you’ll need to drain them. Here’s how to drain a grey water tank on RV.

  1. Always empty the black water first.
  2. Wear rubber gloves
  3. Remove the cap that covers the holding tank outlets, and connect the sewer hose
  4. Put the sewer hose at least 4-5 inches into the dump hole
  5. Secure the hose in place. You can use a brick or the cover of the dumping station to secure the hose
  6. Test the sewer connection by letting a little grey water out first. If there is no leaking, you can empty the black water tank
  7. Open the black water valve. When the tank is empty, open the grey water tank valve
  8. Flush the tanks by refilling them and draining them again
  9. Close the valves and disconnect the hose from the outlet
  10. Lift the sewer hose from the RV end to the dump hole, so any remaining water goes into the dump hole
  11. If possible, run water through the hose to rinse it
  12. Disconnect the hose from the hole and rinse the area around it in case anything spilled. Cover the hole.
  13. Store the sewer hose
  14. Add RV water tank treatment to the tanks. You’re finished!

How to Clean Grey Water Tank for RV

One thing that will make cleaning your RV grey water tank easier is to watch what goes in it. As much as you possibly can, avoid putting food waste, dirt, or grease down your drain – it’s much easier to prevent that than to clean it out once it’s in there! Always empty your tank thoroughly and make sure nothing is left inside, especially if you’re going to store your vehicle for a while.

You can also buy special grey water tank detergents to help clean. They work well, and you can just follow the instructions right on the bottle. If you don’t want to buy the detergent, mix warm water with dish soap and pour it into the tank before a day of driving. The water will splash around the tank. Drain 24-48 hours after putting the mixture in, then flush the tank with clean water. If the tank doesn’t seem clean enough, repeat the process again. You can also use vinegar and baking soda to clean the tank, and people also advise pouring vinegar down the sink every so often to control odors – but be ready for the strong smell when you do!

Plan to clean and sanitize your grey water tanks for RV at least once a year to keep it from developing an odor.

RV grey water tank overflow

You should dump your RV grey water holding tank for RV when it’s ¾ full. Remember, if you’re connected to a line and the washer and dryer are on, you’ll want to keep the grey water tank valve open or you may get water bubbling out of your drains.

When your RV grey water tank is empty, pour some softener and water into the tank to loosen debris that sticks to the sides. This will also prevent odors that could be caused by debris that wasn’t flushed out properly.

If you’re unable (or unwilling) to drive to a dump station each time you need to empty your tank, an RV portable grey water tank can prove useful. You can empty your grey water holding tank into the portable tank and then transport the portable tank to the dump hole for RV grey water disposal.

Treating your RV grey water tank well, cleaning it properly, and disposing of the water will help keep any odors at bay and make your time inside your rig much more pleasant! Happy cleaning!

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