“Clean and flush my hot water heater tank? Nobody said anything about that!”

Your hot water tank needs special care too

you do flush and clean it regularly, right?

As RVers, we’re passionate about keeping things clean and in working order. Forget to sanitize our fresh water tank on a regular basis? No way! Get those holding tanks professionally cleaned every year? You bet! But what about your hot water tank?

How an RV hot water heater works

There are two primary makers of RV hot water heaters, Suburban, used in most fifth wheels, and Atwood, (which is now owned by Dometic, the popular RV appliance and product manufacturer), used primarily in travel trailers. Atwood heaters tend to be smaller (6- or 10-gallon) while Suburban’s are mostly larger (12- or 16-gallons in capacity).

There are three main ways to heat the water in an RV hot water tank: Propane, electricity, or from the heat of the engine. Electric is usually the most convenient, however using the heat from your engine is the most economical (the RV’s drive engine gets hot naturally and you’re just using some of the excess heat to heat up water). Most RV water heaters are dual fuel: electric and propane. Almost everyone with a dual-fuel water heater uses electricity because it’s easier (there’s no pilot to light) and more convenient (just switch on the heater and in a short time, you have hot water).

You can use both electric and gas at the same time — doing so will result in hot water much faster. Water temperature is set at 140 degrees — HOT! — and is meant to be mixed with cold water via a mixing valve to be less scalding (though it can still be pretty hot). You can get after-market thermostats to attach to the hot water tank to fine tune water temperature.

What can go wrong with hot water heaters?

Water heaters, in general, are vulnerable to rusting and corroding, because of the composition of water and the process of how the materials that manufacturers use to make water heater tanks, such as steel, react to oxygen and moisture. There are many issues a manufacturer has to consider when designing their water heaters:

Acidity. Gasses, such as carbon monoxide, naturally dissolve in water, making it highly acidic.

Chemical processes. When steel comes in contact with oxygen or moisture, the process of rusting and corrosion begins.
Heat. Water heaters operate at a high temperature, and heat hastens the process of corrosion.
Different materials. Manufacturers use a variety of materials in designing and building their water heater, and these materials create electrical conductivity, an environment that also speeds up corrosion.

Installing an anode rod — a solid rod of either magnesium or aluminum (often with a little zinc in it) — counters many of the problems inherent to water heater operation. The anode rod succumbs to corrosion before the other components of the water heater. It delivers electrons into the tank, creating an environment that prevents corrosion of the tank and its elements. Experts often refer to the anode rod as the “sacrificial lamb,” because it sacrifices itself to corrosion in order to protect the more expensive water heater.

Generally, Suburban brand water heaters require an anode rod to protect the steel tank from corrosion. The rod is made of a metal that sacrifices itself, so that corrosion will attack the rod before attacking the steel tank. Atwood brand water heaters generally don’t use anodes because their tanks are made of aluminum.

Here’s what Suburban has to say about anodes: “All Suburban water heaters are protected by a magnesium or aluminum anode to prolong the life of the tank. Under normal use, the anode rod will deteriorate. Because of this, we recommend it be replaced annually or when consumption or weight loss of the rod is greater than 75%. Note: Water with high levels of iron and/or sulfate will increase the rate of deterioration. To extend anode life, drain water from tank whenever the RV is not being used. Avoid any extended time of non-use with water in the tank.”

Installing an anode rod in an Atwood water heater is not necessary and, according to Atwood, doing so will void its two-year warranty.

And don’t forget regular cleanings

Cleaning a hot water heating tank? Yep! You should drain, flush and clean your RV’s hot water heating tank twice a year — four times if you are a full-timer. This helps to keep the tank clean, sediment out of your usable water, and everything working properly and for a long time.

The water heater tank in your RV has a curved, convex shape to it (it dips down at the bottom). The drain plug for your tank is located behind an access door, outside your RV. That plus is roughly 1″ above the curved bottom of the tank. And that’s where corrosion and other materials can gather and be hard to get out.

Cleaning your RV’s hot water tank is pretty easy. Just follow these steps:

  1. Turn off your water heater, either inside your RV at the main control panel area and, if there is one, via a small rocker switch on your water heater, outside your rig and behind the access door.
  2. Turn off the water supply to your RV, both the park or shore water and via any onboard pump. You don’t want the RV filling the tank as fast as you are emptying it!
  3. Open the pressure release valve. It’s located at the near the top of the water heater, outside your rig and behind the access door. It looks like a metal switch at the end of a small, short pipe fitting. You may hear sputtering and see water squirt out a bit. This is normal.
  4. Using the appropriate socket wrench size (it varies by manufacturer of the water heater and whether you have an anode installed), slowly loosen the nut at the drain. This is located near the bottom of the water heater, outside your rig and behind the access door. Be prepared for water — potentially pretty hot — to come gushing out!
  5. Using an RV Water Heater Flush Wand (Camco makes them, available at Camping World or Amazon.com), flush out the water heater tank. To do this, attach a garden hose to the wand (which has an on/off switch on it) and turn on the water pressure. Insert the wand into the tank and turn it on. Move the wand in and out, back and forth, and around in a circle.
  6. Water will come out of the water heater tank, along with build-up, corrosion, and hard, calcified material. Keep flushing and cleaning the tank for 5 to 10 minutes.
  7. Let the tank drain. Take this time to inspect the anode if you have one. If it looks very corroded (i.e. you see what looks like a coat hanger wire at the center of it, now exposed) or more than 25% of the anode is gone, it’s probably time to replace it with the appropriate size.
  8. If you have an Atwood water heater and it’s out of the two-year warranty, it’s probably a good decision to install an appropriate sized (4.5″) anode to keep corrosion down.
  9. Replace or install the anode or replace the nylon drain plug. Make sure to use some plumber’s teflon tape to ensure a tight, leak-free connection. Tighten the anode or drain plus securely, but do not over-tighten (especially important for the nylon drain plug which can break if torqued too tight).
  10. Turn on the supply of water to the water heater. You may hear it filling up if you listen closely. It may take 3 to 10 minutes, depending on tank capacity.
  11. Water will spurt out of the pressure release valve (located at the near the top of the water heater) once the tank is full. Snap the release valve closed.
  12. Check the anode or nylon drain plug for drips or leaks. Tighten if needed.
  13. Turn the water heater back on, either inside your RV at the main control panel area and, if there is one, via a small rocker switch on your water heater, outside your rig and behind the access door.
  14. Make sure the water heater is heating water correctly.

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