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Are you preparing your RV for the winter but aren't sure how and when to drain the hot water heater in RVs?

Draining the water out of an RV heater tank is one of those maintenance procedures RV owners need to go through from time to time to ensure that their RV remains operational and avoid costly repairs due to ruptured and busted heater tanks. But what's the big deal with draining your RV's water system, and more importantly, how it's done?

Draining the hot water heater in RVs is a pretty simple procedure: you just need to make the necessary preparations, open up the hot water heater plug and the pressure relief valve, drain the water out, rinse the tank, and close it back up with a new plug. It's really that easy.

While this provides a more direct answer, not all RV heaters are the same, and some models are flushed differently than others. Not to mention the necessary preparations and optional steps you can take to ensure the longevity and adequate functioning of your RV's hot water heater.

To present you with the most comprehensive information that would allow you to DIY drain hot water heater in an RV, we gathered the information from a number of RV owners who drain their vehicle's water system themselves. We then cross-referenced that information with numerous online resources and RV water heater user manuals to help you understand how to DIY drain a hot water heater in an RV. So, without further ado, let's dive right in.



Do You Have to Drain an RV Water Heater?

Before we dive into the DIY guide for draining the RV water heater, let's discuss the reason and importance of draining your RV's water system.

Matter, including solids, liquids, and gasses, contracts in low temperatures, and the same can be said for water in your RV's water system. In fact, water contracts until its temperature drop to approx. 39.2°F or 4°C, at which point water starts crystallizing into ice.

The hexagonal lattice of crystalized water contains more space than the liquid state, meaning that water begins expanding as the temperature drops from 39.2°F to 32°F (from 4°C to 0°C). Once the water reaches a freezing point (32°F or 0°C), it continues to expand by approximately 9%.

This expansion of water in freezing temperatures poses a significant problem for uninsulated pipes and water tanks since the expanding ice can cause the pipes and tanks to burst. That's why it's imperative to drain your RV's water system as you're preparing your vehicle for the winter.

Another reason why you'd like to drain the water system besides winterizing your RV. For example, suppose you're parking your RV for an extended period, in which case it's important to drain its water system to prevent the water from developing bacteria, or going stale.

In fact, it's vital to drain your water heater when storing your RV for longer than two weeks or at the conclusion of every season. Any longer than two weeks, and you're running the risk of water going bad and possibly even harmful to drink.

Essentially, you want to drain the water heater:

  • At regular intervals (at least once a year);
  • Before parking the RV for winter.

Luckily, draining your RV's water heater is a pretty straightforward task — as you'll see from our step-by-stepguide of how to DIY drain your RV's water heater.

How to Drain the RV Hot Water Heater

As previously stated, draining the RV hot water heater is pretty straightforward, and the entire process requires a bit of preparation, followed by three simple steps and perhaps an optional step or two.


Before draining the hot water heater in your RV, you need to make preparations that would make the process safer and less troublesome:

  1. Cut off the water heater's propane gas supply to prevent it from heating up the water.
  2. If your vehicle’s water heater features an electrical mode, ensure that the supply of electrical energy is switched off before draining the water system. The best possible approach is to cut off the supply of electrical power entirely or by simply tripping the water heater's circuit breaker, if any, to cut the power. Cutting off the electrical supply is mandatory if there's no circuit breaker. If you fail to do so, the electric heating element will quickly burn out without any water in the tank.
  3. Open a cold and hot water faucet to release the water pressure after turning off all water entering the RV, including the water pump. Also, it's important to turn off the water pump; operating it without any water in the system could damage the pump.
  4. Allow the water in the heater tank to cool before attepmting  to drain it. Depending on the volume of the heater and the ambient temperature, this might take several hours. However, you can cut the waiting time short by following steps 1 and 2 and opening the hot water faucet before disconnecting the water and disengaging the water pump. That way, you'll flush out all the hot water, after which you can disconnect the water supply and turn off the water pump.

Step 1 — Remove the Drain Plug

Once all the preparations are done, it's time to drain your RV hot water tank. First, find your RV's water heater, which is normally located in an exterior part of your RV. The drain plug for the water heater ought to be in the bottom left corner. You need to remove the plug to drain the water, and how you remove the plug is determined by the type of water heater on your RV.

If your RV has a Dometic RV water heater, formerly known as Atwood water heaters, you need to locate a ½-inch nylon drain plug, which is best removed with an appropriate wrench. However, considering that they're made of nylon, it's easy to break off or round out the corners while removing the plug, so make sure you have a spare plug. Breaking or rounding off the plug poses a massive problem if you're rinsing the system while traveling, so make sure to bring an extra plug.

Suburban RV water heaters are somewhat different, as they're made of steel and equipped with an anode rod, whose purpose is to protect the steel from corrosion by corroding before the tank does. It's an effective solution that typically requires a 1½-inch socket to remove and drain the tank.

Make sure to inspect the condition of the anode rod whilst draining your tank. If it's approximately ¾ or 75% depleted, make sure to replace it with a new one.

Step 2 — Open a Relief Valve

Once the plug is removed, the water will start draining. This can create a vacuum within the tank and the water system, which slows the process down — the air entering the system through the draining hole hinders the flow of water.

To prevent this from happening, open the hot and cold faucets to let the air into the system, or open the pressure relief valve located on the top of the heater, to increase air intake and help the water drain. Once the water stops flowing from the drain hole, you've effectively drained your water heater tank.

Optional Step — Flush the Water Heater

The drain plug in the tank is usually positioned higher than the bottom of the tank, leading to a sediment build-up, which can potentially (eventually) clog up the system. So, before you close up the heater tank, it's recommended that your flush the water heater tank at least once a year, preferably twice. To do this, use a pressurized water source, and rinse out the tank until the water coming out is clean and clear.

Step 3 — Close the Heater and Clean Up

Once the heater is drained, you want to close the faucets and the pressure relief valve and replace the heater's nylon plug (if necessary) or install a new anodized rod. Next, rinse the area with a garden hose, and clean it up with a brrom,  to remove any dirt and debris from the RV water heater, and close the panel door.

Coming Out of Winter's Slumber

Another equally important step is to rinse out your RV's water heater tank after the vehicle has spent the winter in storage. Make sure to flush the RV's water system before refilling it. This is especially important if you have used RV antifreeze (propylene glycol) in your water system over the winter.

Unlike car antifreeze, which is a toxic chemical used as an over-the-winter engine coolant, propylene glycol is an RV-specific, non-toxic and non-flammable antifreeze that doesn't taint the water. Still, it's a good idea to rinse the water system out, including the RV water heater tank, before refilling it with water.

Also, you shouldn't neglect your fresh water tank and freshwater lines, as those often need to be drained and rinsed during the winterization of your rig, as well as part of the RV water lines' regular maintenance. The draining process might be different, but the same basic rules apply.