How to Sanitize an RV Fresh Water Tank

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Sanitizing your RV's fresh water tank is an essential maintenance item that is often overlooked. Over time, microorganisms can build up on the inside walls of the tank, contaminating any water put in to the tank. Even if you use a quality water filter when filling the tank, bacteria, viruses and protozoa can multiply quickly if the fresh water tank is not disinfected periodically. This can contribute to foul smelling and poor tasting water, even health issues. But sanitizing your RV's fresh water tank is easy.

Items you will need

  • 1 1/16" or 27mm &frac12;" drive socket

  • &frac12;" extension

  • &frac12;" ratchet

  • 1 cup non-scented liquid household bleach

  • Fresh water supply

Drain the Fresh Water System

Step 1

Find a suitable location for your RV where you can drain the fresh water tank and where there is a nearby fresh water supply. Turn off your RV's water pump and water heater.

Step 2

Locate the fresh water tank drain valve and open fully. The valve is generally located underneath the RV near the lowest point on the fresh water tank and may be gray or black in color. It may take five to 10 minutes for the tank to fully drain.

Step 3

Open the exterior cover to the water heater. Allow the water heater too cool for one hour if it has been recently used. Open the water heater relief valve located near the top of the water heater tank. Water will spray out of the valve until all the pressure in the tank is gone.

Step 4

Locate the water heater drain plug near the bottom of the tank. Loosen the drain plug with the 1 1/16-in. socket. Slowly remove the plug with your fingers. Water will run out of the drain hole so stand to one side to avoid getting wet.

Fill and Sanitize the Fresh Water Tank

Step 1

Close the fresh water tank drain valve, re-install the water heater drain plug, and close the water heater pressure relief valve.

Step 2

Pour 1 cup of bleach in to the fresh water tank inlet. Fill the fresh water tank completely with clean, filtered water. If you do not have a water filter, use a chlorinated water supply. Otherwise use 1½ cups of bleach.

Step 3

Turn on the water pump and wait for the water heater and water lines to fill. The pump will run for one to three minutes until the system is fully pressurized.

Step 4

Open the hot water faucet furthest from the water heater. Run water until you smell the odor of chlorine. Repeat this step for each hot and cold water faucet. This step ensures that your fresh water tank, water heater, and water pipes are being sanitized.

Step 5

Allow a minimum of three hours for the chlorine in the bleach to kill any microorganisms in your RV's fresh water system.

Complete the Sanitation Process

Step 1

Turn the water pump off, drain the fresh water tank, and drain the water heater using the steps from Section 1.

Step 2

Refill the fresh water tank, turn the water pump on, and wait until the fresh water system is fully pressurized, including the water heater.

Step 3

Repeat Step 4 in Section 2 until you cannot smell any chlorine, approximately one minute for each faucet, as the strength of the chlorine to water ratio is very high during the sanitation process.


  • Even after sanitizing your RV&#039;s fresh water tank, there may be excessive sludge and microorganism buildup that cannot be killed or removed with household bleach. If you continue to experience foul-smelling or poor-tasting water, have an RV technician inspect your tank as it may require replacement.


  • Sanitize your fresh water tank, water heater, and plumbing system often, especially if the weather is hot or your RV sits for an extended period of time with water in the fresh water tank.