RV Water Heater Flush

Motorhome, camper, travel trailer, or fifth wheel – if your RV has a water heater, you need to maintain it, including a regular flush.

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It’s a good idea to inspect your RV water heater at least twice a year. If you live someplace where you store it in the off-season, the best two times to inspect the water heater would be just before storing it, and as part of your de-winterization.


You’ll find your water heater inside an access panel on the outside of your RV. Although tankless water heaters are gaining popularity for RV’s, your heater will most likely be the variety with a tank. Your RV water heater will use propane, electricity, or a combination of electricity and propane to heat the water.

Begin by looking for obvious leaks, rusty fittings, cracked hoses and lines, loose wires, insect or rodent infestation. If any problems are spotted, most can be fixed with standard plumbing or electrical parts from hardware stores. If a specialty part is needed, you can visit your local RV parts department.

Unless your RV water heater has an aluminum tank, it will have an anode rod. The anode is a solid metal probe-like cylinder that inserts into the water heater tank and then threads shut – often into the drain opening. The anode is there to stop the chemical reaction that creates rust by sacrificing itself (which is why they’re sometimes called sacrificial nodes) and attracting that reaction to itself.

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It’s important to check the anode rod at least once a year. When the rod has lost about three-quarters of its mass, it’s time to replace it. Replacing it too late, or not at all, will lead to premature RV water heater tank deterioration and replacement. Fortunately, you’ll only have to replace it, on average, every couple of years, and they’re very affordable (especially compared to the cost of a replacement RV water heater).

So let’s replace the anode in your RV water heater. If your heater tank doesn’t have an anode rod, it’s still a good idea to flush the heater once a year to get rid of any sediment or debris that could affect the heating ability and lifespan of your tank.

If you haven’t done so already, disconnect any water supplies to your RV. Also make sure the water pump is turned off. Then open all the cold and hot water taps in the RV to relieve any pressure that might have built up in the system.

Turn off the power or propane to your water heater, and ensure that it doesn’t contain any heated water. The last thing you want to do is burn yourself. It’s a good idea to tape over any gas valves or power switches so that no one accidentally powers up the RV heater when it’s dry. Doing so can destroy the heating element or the heater, and possibly start a fire.

If your RV water heater has a bypass, use it to close off the water to the heater – otherwise you’ll have to deal with water draining from the entire system via the heater tank’s drain hole – doable, but not ideal.

Use a wrench or socket top remove the drain plug and anode rod. Allow the water to drain completely from the heater tank. You can open the relief valve to make the draining go faster. Note that there may be rusty water draining from the tank and that it might stain a concrete driveway. If that’s a concern, find a way to divert the water – perhaps draining into a bucket, or using a length of plastic pipe.

Now you need to get fresh water into the tank. The easiest and most thorough way is with a flushing wand – also called a tank saver by some people. It’s simply a narrow hose that hooks up to your water supply line and most often has a bit of a bend at the end. The tank wand attachment is narrow enough to be inserted in through the RV water heater’s drain opening. Keep flushing until the water runs clear, remembering to rotate the hose so that the bend at the end of the wand directs the water all over the interior of the tank.

If you don’t have a tank wand, you have a couple of options. One, jury rig something with adapters you can buy and a length of tubing or, instead of proper adapters, use copious amounts of electrical tape and duct tape. Two, turn RV’s water supply back on – open the bypass if you closed it earlier – and let it go until the water runs clear.

Have you ever turned on your RV’s hot water tap and been hit with that rotten egg sulfur smell? It’s almost enough to make you consider abandoning the RV. Fortunately, it’s a common problem with a simple solution. You just have to add a step to flushing the tank.


If you arrived at this article because of the sulfur smell from your hot water taps, you’ll need to use vinegar as part of the flushing process. The cause of the rotten egg odor is a reaction between aluminum or magnesium in your RV’s water system and anaerobic bacteria. Vinegar kills this bacteria and reacts with any mineral buildup to break it down.

Make sure the drain plug is in, and the taps in the RV are closed.

If you have a winterizing diverter — usually used to suck antifreeze into the system – you can use this to get vinegar into your RV’s water heater tank. If you don’t, you’ll have to improvise. One method is to use a flexible length of tubing fitted to a funnel at one end, with the other end placed into the opened relief valve (you may need to use some plumbers putty or similar to make a good seal).

You want to end up with about a 50/50 mixture of vinegar and water in the tank so, for a 10-gallon tank, add 5-gallons of vinegar and finish up with 5-gallons of water.

Once you have the vinegar in the tank, adding the water is easier. Leaving the drain plug in and the relief valve open, open the bypass, and turn on the water supply to your RV. When water starts to come out of the relief valve, close it immediately. If you listen closely, you’ll still hear water running as the water heater tank tops off.

Turn off the water supply and let the mixture sit for at least a few hours, preferably overnight.

Make sure your RV water supply is turned off and turn the bypass off. Carefully open the relief valve on the water heater tank to, obviously, relieve pressure. Then open the drain plug and allow the tank to drain completely.

If you have a tank wand, use it to thoroughly rinse the tank. If not, replace the drain plug, and fill the tank until the relief valve shows water, close the relief valve, and wait for the tank to top off. Drain. Repeat a couple of times.

If you’re replacing your anode rod, now is the time to insert it. If the rod is only a year old and has more than 50% of its mass, you can reuse it if you like. Wrap Teflon tape on the threads of the anode rod and drain plug for a tighter fit. Note, the Teflon tape isn’t there to plug gaps, it’s there to lubricate the threads so you can get a tight fit.

If you’re going to sanitize your whole system, now would be the time. If not, with the RV water heater tank relief valve open, turn on your water supply. When water comes out of the relief valve, shut it off. Open the bypass. Then go through your RV opening up all the taps to flush out any remaining vinegar and any air in the lines.