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Dumping your gray water holding tank is a straightforward process. It is similar to dumping the black water holding tank but with fewer steps. Here are our recommendations for how to properly dump the gray water holding tank.

List Of Supplies

Supplies for cleaning and dumping the RV gray water holding tank
Supplies for cleaning and dumping the RV gray water holding tank

Steps To Follow

Deep Cleaning The Gray Water Holding Tank

If you are wanting to fully clean out the gray water holding tank, the process starts the evening before you plan on dumping the gray water holding tank.

RV gray water holding discharge valve in the closed position with the clear elbow and sewer discharge hose attached
Gray water holding discharge valve in the closed position
  • Close the gray water shut off valve if you left it open while set up at camp.
Pouring a full bottle of Dawn dish soap into the RV kitchen sink to be rinsed with water into the gray water holding tank
Pouring a full bottle of Dawn dish soap into the RV kitchen sink to be rinsed with water into the gray water holding tank
  • With your gray water holding tank nearly full, pour 20 ounces or more of Dawn Ultra into the kitchen sink.
Dawn dish soap being rinsed past a clear p trap with water and into an RV gray water holding tank
Dawn dish soap being rinsed past the p trap with water and into the gray water holding tank
  • Follow that with running water at the sink to move the Dawn past the P traps and HepvO waste valves and into the gray water holding tank.
Soap bubbles coming up from the lowest drain in the RV indicating the gray water holding tank is full
Soap bubbles coming up from the lowest drain in the RV indicating the gray water holding tank is full
  • You will see soap bubbles coming up from the lowest drains in the RV, typically the shower(s).
  • Let this solution sit in the gray water holding tank overnight.

Dumping The Gray Water Holding Tank

After deep cleaning the gray water holding tank or when it is full, follow these steps to dump the gray water holding tank.

Sewer discharge hose connected to the RV discharge manifold for dumping the gray water holding tank on sewer discharge hose support
Sewer discharge hose connected to the RV discharge manifold for dumping the gray water holding tank
  • Connect the sewer discharge hose to the RV discharge port.
Clear elbow at the end of the RV sewer discharge hose to be inserted into the sewer port
Clear elbow at the end of the sewer discharge hose to be inserted into the sewer port
  • Connect the other end into the sewer drain opening at the campsite or dump station.
Opening the RV black water holding tank valve to dump the contents
Opening the black water holding tank valve to dump the contents
  • If you are dumping the black water holding tank as well, dump the black tank first, leaving the gray water holding tank valve closed.
Gloved hand closing the RV black water holding tank discharge valve after dumping the contents
Closing the black water holding tank discharge valve
  • Keep the black water holding tank valve closed to prevent tank contamination while dumping the gray water holding tank.
Open the grey tank valve to allow the grey water to partially rinse out the sewer hose
Open the grey tank valve to allow the grey water to partially rinse out the sewer hose
  • Open the gray water holding tank valve, which will allow the gray water to rinse the inside of the sewer discharge hose.
  • While at the dump station, use the water supply to rinse the sewer discharge hose while it is still attached to the sewer port.
  • Due to the P traps or HepvO waste valves present  in every sink or shower to stop sewer gasses, a backflush is far less effective for the gray water holding tank.
RV sewer discharge hose with p trap added to it along with water in the p trap resting on sewer hose support
Sewer discharge hose with p trap added to it along with water in the p trap
  • If you are at a campsite with a sewer drain opening, you can then leave the gray water holding tank valve open and put a P trap bend in the discharge pipe and add some water to the P trap.
  • However, if the campground only has a dump station, close the gray water valve.

You have now successfully dumped your RV gray water holding tank! Congratulations!

If you would like to read about how to dump the black water holding tank, check out this article!

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