How to Clean a Gray Water Tank in an RV

How to Clean a Gray Water Tank in an RV
Recreational vehicles have three holding tanks: one for human waste from toilets, one for storing fresh water and one for gray water. The gray water tank on an RV holds waste water from the shower and sinks. They need to be emptied when full and should be cleaned at the time of emptying. Using a little water softener in the cleaning process will help remove soap buildup in the tank. Properly cleaning the tank each time will make the task easier and will eliminate odors.


Difficulty: Easy

Things You’ll Need:
  • Sewage hose
  • Garden hose
  • Tank flush fitting
  • Water softener
  • Bleach
Step 1
Connect the tank flush fitting to the outlet.
Step 2
Attach the sewage hose and garden hose to the flush fitting.
Step 3
Put the open end of the sewage hose into the tank dump station. This will likely be a pipe in the ground slightly bigger than the hose. Use the cover or a rock to hold the hose in place.
Step 4
Open the valves on the flush fitting and the outlet on the RV. Allow the tank to empty. Leave the sewage outlet valve on the RV open until you are finished cleaning the tank.
Step 5
Close the sewage hose valve on the flush fitting after the tank is empty.
Step 6
Dissolve 2 cups of water softener in a gallon of hot water and pour down a sink drain.
Step 7
Backfill the tank by turning on the water to the garden hose. Use care not to overfill the tank.
Step 8
Shut off the water to the garden hose.
Step 9
Open the sewage hose valve on the flush fitting to drain the tank.
Step 10
Backfill the tank with water using the garden hose and drain. Repeat until the water runs clear. Do not add water softener each time. The one rinse with it will be enough.
Step 11
Fill the tank with fresh water and pour 1/2 cup of bleach down a sink drain.
Step 12
Drain the tank a final time.
Step 13
Close the outlet valve on the RV. Disconnect the hoses from the flush fitting and remove the flush fitting.

Tips & Warnings

The tank flush fitting has a garden hose fitting as well as a sewage hose fitting and a valve to shut off the sewage hose for flushing. Get one with a clear plastic elbow so you can see your progress.
Always clean the holding tanks from dirty to clean. The cleaner water from the gray tank and fresh water tank will clean your sewage hose.
Do not keep the drain valve open when you are hooked up to services. The water will run out leaving behind solids.
Some places require sewage hoses not come into contact with the ground. You can get support devices that fold up for easy storage.
Never dump gray water on the ground. This is a source of pollution and you can get fined for this.

Article Written By Mark Quest

Mark Quest began his writing career in 2009, contributing to various online publications. He attended Asheville Buncombe Technical Community College, focusing on the sciences.

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