RV Water Heater Flush with Anode Replacement

Why do you flush out your RV Water Heater?

Water flowing out of atwood rv water heater with relief valve open

With our experience living in our 5th wheel for almost a year and a half, flush out your RV hot water heater at least one time per year is absolutely necessary. Unless your hot water tank is made of aluminum, the metal parts will corrode sitting in water.

Depending on how hard the water is that is sitting in your hot water tank, calcium deposits form on the inside of the tank along with other sediment that settles to the bottom of the tank. It is best to rinse the tank clean to prolong the life of the hot water tank.

What does the Anode do?

Anode for atwood rv water heater

To save the metal parts inside our hot water heaters from corroding, we use an anode made of magnesium attached to the drain plug of the water heater tank. The magnesium is more corrosive than the metal used in the hot water heater and will take the corrosion over the metal parts. Thank you anode!

It is recommended to replace the anode one time per year. The anode should be highly corroded when removed.

My Experience with the flush out of our Atwood Water Heater

Atwood RV Water Heater

The first time I flushed our Atwood Water Heater in our twenty year old 5th wheel, I was surprised by the amount of sediment, corrosion, and other material that flowed out. The anode/drain plug to the water heater tank was easily unscrewed the first time. I used our tank rinser to flush out the inside of the tank 4-5 times until the water ran clear and chunk free.

This last time I did the flush and replaced the anode, the anode was corroded to the threads on the inside of the drain pipe. I tapped the bolt end of the anode with a hammer a few times and was then able to force the bolt to unscrew. When I removed the old anode, no water ran out. I looked inside and could see the magnesium anode in the middle of solid corrosion. Yikes!

Pick and Hammer
Cleaning out RV Water Heater drain corrosion

A pick tool, ice pick looking tool, and a hammer came in handy to chip the corrosion away piece by piece. After I was able to clear the corrosion clog and the water drained, I cleaned the threads to the drain pipe with a small wire brush.

Flushing the inside of the tank out with the hot water tank rinser worked great. The tank was rinsed and filled about eight times until I could not see calcium deposits or corrosion chunks flowing out.

How to Flush your RV Water Heater and Replace the Anode

Tank Rinser, 21 mm socket wrench, plumbers tape and anode for Atwood water heater all used to flush our RV water heater

Equipment Needed

Tank Rinser

Anode for Atwood Water Heaters

Anode for Suburban or Mor Flo RV Water Heaters

Plumber’s Tape

1/2″ Drive 21mm Socket, 1/2″ Drive Socket Wrench, and 1/2″ Drive 10″ Extension

First Things First

Turn power off to RV Water Heater before the flush

before you flush your RV water heater is to turn the power off to your water heater at your RV’s circuit breaker. Turn the propane off at the tank if you use propane. We do not want the tank to heat while we are cleaning it. The heating elements could be damaged if left on with out being submerged in water.

Flush out hot water from RV water heater

Run the water in your sinks and/or shower until the water runs cold. You do not want to drain hot water. The water comes out fast once you remove the plug.

turn water off to RV

Turn the water off going to the RV. The valve is closed when the handle or lever is positioned 90° to the pipe. When you remove the anode, the water will continue to fill the water heater tank if the water is left on on to the RV.

Draining the Hot Water Tank

Removing the anode from the RV water heater tank

Unscrew the drain plug/anode. The anodes I use need a 21mm socket wrench and a 10″ socket extender to loosen and be aware, a 21mm socket is a pretty big socket so be make sure you have a socket that big.

water flowing from rv water heater with relief valve closed

When you unscrew and remove the old anode, the water will flow out slowly.

Opening the relief valve of the RV water heater tank

Open the breather valve at the top side of your water heater. This allows air to flow in and water to flow out of the water heater tank.

water flowing out of water heater with relief valve open

Flushing the Hot Water Tank

flushing out Atwood RV water heater

When the tank is empty, slide the tank rinser into the tank through the drain pipe. Open the valve all the way on the tank rinser allowing water to spray into the tank. Push the rod in and out, twisting side to side making sure to spray all inside surfaces clean with the high pressure water.

I cannot remember where I read, but I read not to spray strait up. The heating element is on the top side I believe and maybe it is to not damage that. I personally close the valve on the rinser a little bit and spray up to rinse anything that can be rinsed off.

flush milky water from RV water heater

Keep moving the sprayer around hitting all inside surfaces until the tank is about full. Remove the rinser and allow the water to drain. You will see the water is cloudy white and has white chunks. Repeat the rinsing process as many times as necessary until the water flowing out is clean and clear. I rinsed my tank about ten times to have clean water free of white chunks flowing out.

Use a clean rag around your finger and clean out the threads on the inside of the drain pipe. Rinse the pipe clean with the tank rinser.

Replacing the Anode

plumbers tape on anode threads for the rv water heater

Wrap a few layers of plumbers tape around the treads of the new anode. I am not a plumber but I like to use plumbers tape to help ensure a good seal. Slide the anode into the drain and hand tighten the anode into your water heater’s drain. Use your 21mm socket wrench to tighten the anode.

placing anode into RV water heater drain

I go pretty tight and come back a little later and give it another crank to make sure we’re tight and not dripping. I often times get it a little tighter if I come back after it has sat with water in the tank for a while.

Tightening the anode into the RV water heater drain after the flush

Filling the Hot Water Tank

open relief valve in the rv water heater tank to flush

Turn the water back on to your RV. Make sure the pressure relief valve is open to allow air to flow out as water flows in and then close the pressure relief valve as soon as water comes out.

water coming out of the open relief valve of the rv water heater
closed relief valve after the rv water heater flush

Turn the hot water on at the faucets and shower to allow the air trapped in the lines and the tank out. Let the water run for a few minutes or until you do not see or hear any more air coming out of the faucets.

flushing air from the hot water line after the rv hot water heater tank flush

Final Steps

turning on the power to the electric water heater after the flush

Turn the circuit breaker back on to the water heater and open the propane tank to the RV if you use propane. You are now making hot water in your newly flushed water heater with its new anode.

Watch me flush our Atwood water heater and replace the anode

More from TheWildWaynes


Watch Me Replace our RV Toilet video


Watch Me Silence our Loud Water Pump in our RV video

Mountain Clouds Video by DistillVideos from Pixabay

2 Comments on “RV Water Heater Flush with Anode Replacement

  1. Pingback: Reseal your RV - TheWildWaynes

  2. Pingback: Big Bend of The Colorado River, Camping - TheWildWaynes

Leave a Reply