How to Replace an RV Fresh Water Tank

Two RVs in the snow.

When traveling the open road in your RV, it's important to make sure that you have access to fresh, clean water. The water that is used for washing, bathing, and toilets is held in the fresh water tank. If your fresh water tank becomes damaged or no longer functions, it will need to be replaced.

Purchase a Replacement Tank

RV replacement tanks are available in a wide variety of shapes, sizes, outlet valve arrangements. Before you can purchase your replacement tank, you need to know the dimensions and valve configuration of your existing tank. Once you have this information, you can purchase a replacement tank online or from an RV dealer. Most tanks are made of polyethylene plastic, which is not compatible with sealants, greases, petroleum jellies, glue, or other additives. Be sure not to use any such items during your replacement process.

Check Your Plumbing

Fresh water tanks in RVs require a 3-inch inlet and a 2-inch vent. These must be placed at the highest point of the tank, which may require that you drill the necessary holes in the proper location to suit your plumbing configuration. You may want to purchase a rubber grommet along with your replacement tank to help with the piping installation.

Once your replacement tank arrives, you're ready to begin your installation.

Step 1 - Clean the System

Start by cleaning out the fresh water system of the RV. All pipes should be drained. Drain the water heater and remove any and all filters.

Step 2 - Feed the System

Mix together 4 teaspoons of liquid soap to every 10 gallons of fresh water. Feed this through your system and run all taps until the soap is completely gone. Fill your system with fresh water and drain again.

Step 3 - Replace the Tank

Following the manufacturer's instructions, replace the existing fresh water tank with the new one and check for leaks.

Step 4 - Santize

Once the installation is complete, use chlorine bleach to sanitize your freshwater system. Fill your new fresh water tank half way with fresh water. Add 6 ounces of bleach for every 10 gallons of water in the tank.

Fill the rest of the tank with fresh water and let it sit for at least one hour in the tank. After an hour has passed, open all faucets and drain out the chlorinated water.

Be Prepared to Repair

An RV on the road.

If you're on the road while you're waiting for your replacement tank, you may need to repair the existing tank until your replacement arrives.

Step 1 - Drain

Drain the tank immediately and locate the cracked area. Remove the tank completely if the repair must be done in a hard to reach spot.

Step 2 - Drill Holes

Drill two tiny holes at either end of the crack that you're fixing, and then sand the area surrounding the crack. Try to create a rough surface that a patch can stick to easily.

Step 3 - Cut a Patch

Cut a fiberglass patch that's two inches larger then the crack all around.

Step 4 - Cover the Patch

Mix epoxy resin with its catalyst and cover the patch completely with this mixture once the patch has been placed over the cracked area.

Let the fresh water tank sit for 24 hours. Refill and check for leaks.