The best way to flush an atwood RV water heater

The Best Way to Flush an Atwood RV Water Heater

Updated on January 30th, 2024

Does your RV have an Atwood water heater?

Atwood is a popular brand of water heater that is used in many RVs. Learning when and how to flush the unit is part of keeping your RV in top condition.

To help you maintain your water heater, I put together this quick reference guide to flushing an Atwood RV water heater and teach you how to clear away hard water mineral deposits.

When you know how to maintain your Atwood water heater correctly, you can avoid RV damage and expensive repairs or replacement of the unit, which means more money in your pocket for camping fun!

When to Flush an Atwood RV Water Heater

Many new RVers fail to understand the importance of maintaining their water heater and only give it a thought when the tank rusts out and starts to leak or the heating element or other parts quit working.

If your RV is a recently used purchase, you’ll want to flush the water heater immediately. The previous owner may have neglected this task, and flushing it out will give you a better idea of its internal condition.

It is essential to note that Atwood water heaters do not use an anode rod. Instead, the tank itself works as one large anode rod, which many people who switch RVs to one with an Atwood model find confusing.

Typically, you should expect to service an RV water heater at these times:

  • Once or twice a year, depending on how often you go camping
  • Always flush (and drain) the water heater before winter storage
  • Anytime an unpleasant smell comes from the hot water faucet
  • Every three months, if you know the water source is hard

Most RV water heaters do not have an aluminum tank, which resists corrosion. This detail is why you need to regularly flush out the mineral sediments that collect at the bottom of the tank before they wear down the liner and rust the metal underneath.

TIP: Using a water softener in your RV, especially if you are full-time, will significantly reduce mineral deposits and damage inside your water heater tank.

How to Flush an Atwood RV Water Heater

There are many steps to flushing an Atwood water heater for an RV, but none of them are difficult if you know what order to proceed and have the correct tools on hand.

Gather these tools to make the job quick and easy:

  • 15/16″ 12-point socket, swivel adapter, 4″-5″ extender, and a ratchet handle
  • Pair of large channel lock pliers
  • Section of clear tubing 18″ long and 1/2″ diameter with a funnel on one end
  • 3 gallons of white vinegar
  • Tank flush wand
  • Large tub that can catch tank drainage
  • Teflon pipe thread tape
  • Replacement drain plug (optional)
  • Rags

Steps to Flush an Atwood RV Water Heater

Atwood RV water heater

Step 1. Turn Off RV Electricity and Propane

Flip the water heater circuit breaker inside your RV, and for total safety, unplug the camper from shore power.

If your water heater uses propane, turn off the valve on the tank so no LP will run to the water heater while you work on it. Leaving the heating element on will burn up and damage the component if no water is present.

Step 2. Run Water in RV

To prevent scalding hot water from draining from the tank during the flush, open your faucets in your sink and let the water run.

Once the hot water dissipates, you can shut the water back of at the sink.

Step 4. Turn off the Water Source to the RV

Sanitizing an RV water tank

Turn off the spigot that feeds your RV water hose that connects to the water inlet port.

Once you stop the water, go inside your RV and open the sink faucets again. This step will allow any water to flow out and let air backflow into the plumbing pipes, releasing the water pressure.

If you don’t turn off the water, the RV plumbing system will keep sending water to the water heater tank, and it will never drain so that you can flush it out.

Step 5. Remove the Plug and Drain the Hot Water Tank

Open the exterior RV water heater access door so you can see the backside of your unit.

Near the bottom left-hand side of the water heater, you’ll see a large metal plug. This plug is partially hidden under the piping for the propane and will have a downward tilt.

You’ll use the swiveling adapter with the socket and extender to sneak in underneath the propane components to attach the socket to the drain plug. The extender will allow you to clear the edge of the RV as you turn the ratchet handle to twist out the drain plug.

If the water heater isn’t regularly maintained, you may have difficulty getting the drain plug to unscrew.

Having a longer handle on your socket wrench will give you more force to break it free. You can also spray the threads around the plug with a product like PB Blaster to help loosen any corrosion or rust, making it stick.

When you unscrew and remove the plug, the water will begin to flow out slowly, so be ready with a bucket to catch the water if you don’t want to stand in a puddle to finish the task.

Step 6. Open the Water Heater Pressure Relief Valve

Once you have your feet clear or your bucket in place, open the pressure relief valve found on the upper portion of the tank. The valve will look like a protruding brass water fitting with a lever at the end.

Take the lever and lift it so it remains standing straight up from the top of the valve.

This action will let air into the water heater tank, which will allow the remaining water inside the tank to flow out much more quickly.

RV Water Heater Pressure Relief Valve Function (Video)

Step 7. Replace the Drain Plug and Remove the Pressure Relief Valve

Once the water stops flowing from the water tank, replace the drain plug.

Move up to the pressure relief (or high-pressure) valve, and use the channel-lock pliers to unscrew the fitting from the tank.

This port is where you are going to fill the tank with the water and vinegar solution that will break down any mineral deposits stuck to the interior of the tank.

Step 8. Use Tubing to Fill Tank with Vinegar Solution

Slide the thin end of the tubing into the opening, where you took out the pressure relief valve. Push it down far enough not to slip back out of the hole when you start pouring liquid through it.

Start with your vinegar, and pour all three gallons into the water heater tank, using the funnel on top to reduce spillage.

Step 9. Clean Up and Reinsert the Pressure Relief Valve

While you’re waiting for the vinegar solution to break down mineral deposits in your RV hot water tank, it’s a good time to clear off the old pipe thread Teflon tape from the fitting.

Look inside the opening of the RV and remove any mineral build-up on those inner threads and on any part of the valve.

Once clean, dry and prep the valve threads by applying new Teflon tape by wrapping it clockwise several times around the fitting.

Replace the valve on the RV, and use the channel locks to tighten snugly, but do not overtighten. The drain port should face downward when properly installed, which is helpful to know when you have it tight enough.

Step 10. Fill the Rest of the Atwood Tank with Water

After the pressure relief valve is in place, open the lever on the end.

Reconnect the water supply hose to your RV by turning on the water spigot. Allow the water to flow into the hot water tank until it’s completely full. When the tank is full, excess water will overflow through the pressure relief valve.

As soon as the water dribbles out of the fitting, flip the lever to close the valve.

Step 11. Turn the Water Heater Back On and Let the Cleaning Solution Soak

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You want the water inside the tank to warm up for best results with the vinegar solution, which means you’ll need to return propane and power to your RV by reversing Step 1 above.

Wait for 30 minutes, then position a cup beneath the drain of the relief valve. Gently open the lever just enough to let a small quantity of the vinegar solution trickle out into the cup. Afterward, promptly close the lever.

Letting a bit of the vinegar solution go through the valve will clear away any mineral deposits you missed when cleaning it before reinsertion.

It would help if you left the tank with the vinegar cleaning solution soaking for 12-24 hours or overnight to break down any stubborn deposits fully.

Step 12. Turn Off the Water Heater and RV Water Supply, and Open a Faucet

It’s time again to turn off the water heater and shut off the water supply to the RV. Then, go into your camper and open a hot water faucet to relieve the pressure in the plumbing lines to the water heater.

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You will see and smell the vinegar solution coming from the faucet when you turn it on. After several seconds, the liquid should stop flowing.

Step 13. Drain the Water Heater Tank Again

Now it’s time to drain the vinegar solution out of the water tank.

CAUTION: The water inside the tank is hot, so put on protective gloves and clothing and be prepared to step away from the draining water as it flows out of the drain hole.

Using your socket tools, unscrew and remove the water heater drain plug. After the plug is out and the water is flowing, stand to the side and open the lever on the pressure relief valve to allow the water to drain out quickly.

Leave the plug out once the water drains, and let the tank sit for an hour to cool down before the next step. It’s possible to crack the inner tank by spraying cold water onto the hot metal, so letting the tank cool down reduces this risk.

How to Drain & Flush a Hot Water Tank (Video)

Step 14. Flush the Tank

Take your RV water heater tank flushing wand and attach it to the end of your garden hose.

Turn the water supply back on, and stick the end of the wand into the drain plug opening. Twist and turn the wand around inside the tank, moving it in and out as far as you can to reach as much inner surface as possible.

Don’t forget to shoot the water straight upward to rinse off the heating element.

Water will flow from the drain hole while you rinse out the tank with the wand, bringing along with it chunks of mineral deposits the vinegar clears from the tank walls.

Keep working the wand inside the tank for 5-10 minutes or until you don’t see debris rinsing out of the tank.

Once you feel the tank is adequately flushed, turn off the main water supply to the RV and let any remaining water drain out.

How to Clean an RV Water Heater the Right Way (Video)

Step 15. Replace the Drain Plug and Finish Up

You can opt to reuse the original drain plug already in your RV Atwood water heater, but you’ll first want to clean the Teflon tape from the threads and clear away any debris from the threads inside the opening to the tank.

The better solution is to purchase replacement Atwood water heater drain plugs. The plugs come in a two-pack and are around $10.

These replacement plugs do not require Teflon tape, as they seal tightly without it and consist of a hard nylon material that doesn’t interact with the metal and causes corrosion like a brass or metal drain fitting would. Use your socket to snug up the drain plug, but do not overtighten.

Now, you can turn your RV water supply back on and let the water heater tank refill. Next, open the lever on the pressure relief valve to allow the water to enter the tank faster.

After the water begins to flow out of the relief valve, flip the lever shut. You can now return power or propane to the tank to let the water heat up.

It’s only temporary if you smell any vinegar from your faucet or shower after flushing the water heater. After only a few seconds of use, any residual vinegar solution pulled into the hot water plumbing lines will rinse away, and you can resume normal water use inside your RV.

Replacing RV Fresh Water Low Point Drain Plug (Video)

Final Thoughts

Taking short showers in an RV is already a challenge, but taking a COLD short shower because your water heater failed is even worse!

Please don’t risk your Atwood RV water heater breaking down by taking care to flush and maintain all its components properly. A new unit is expensive to replace and will cut deeply into your RVing budget.

By following this guide to RV water heater cleaning and flushing, you’ll keep your motorhome, fifth wheel, or travel trailer in top shape so that you can enjoy hot water on every camping trip!

"Man cannot discover new oceans unless he has the courage to lose sight of the shore."
-- Andre Gide

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