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How To Fix Common RV Tankless Water Heater Problems

male hand under water coming from an outdoor rv shower with trees in background
Having problems with your RV tankless water heater? Here’s what you can do. Photo from Shutterstock

RV Tankless Water Heater Problems & How To Fix Them

RV tankless water heaters have brought the convenience of instant hot water to the RV world. A tankless water heater heats water as it’s used, so there is no need to store hot water in a tank. With water heated on demand, you not only save space, but you can lighten the load in your RV by as much as 300 lbs because you’re not storing hot water.

The most common tankless water heaters for RVs are made by just three manufacturers: Atwood, Suburban, and Girard. There are many other brands out there that will work perfectly in an RV too.

Any tankless water heater will heat water quickly as soon as a hot water tap is turned open. The result is that you won’t use nearly as much energy to heat your water as you would with a traditional RV water heating system.

RV tankless water heaters also have a reputation of being longer-lasting than traditional water heaters, leading to lower overall costs.

Another big advantage of a tankless RV water heater is that there is no requirement to reheat the water between tasks like doing the dishes and having a shower. Family members can also take showers one after another, with no downtime while the water reheats.

The downsides of RV tankless water heaters

RV tankless water heaters have some drawbacks as well. This means a tankless water heater won’t be absolutely perfect for every RVer.

Singular power source

Traditional RV water heaters give you a choice between heating water with propane or electricity. RV tankless water heaters are one or the other. That being said, most RV tankless water heaters operate on propane. This is because of the high amperage requirements of electric tankless water heaters.

Having a single power source to heat hot water can be a problem, especially for RVers who prefer the versatility of being able to choose between propane and electricity.

The real cost of an RV tankless water heater

RV tankless water heaters have a reputation for being really expensive. Actually, the price of an RV tankless water heater ranges between $100-$800. Many tankless heaters can be found for around $400.

If you’re handy, you might do the installation yourself. If you aren’t handy, it should take under an hour for a professional RV technician to install a tankless water heater for you. Whether you heat water in your RV with propane or electricity, you’ll quickly recover the cost of buying and installing a tankless water heater in your RV by using less power.

What are the most common RV tankless water heater problems?

There are five common RV tankless water heater problems. We’ll break down each of these problems and tell you how to deal with them:

1. Cold water sandwich

This is a common RV tankless water heater problem for families that take back-to-back showers. What happens is this: Someone takes a shower. The next person goes to have a shower and luxuriates in the warm water for a few moments. The next thing they know, they are being blasted with cold water. After they finish jumping out of their skin in shock, it gets nice and warm again.

So, why does this happen? The reason is that the tankless water is heating water as it is going through. The first person gets out of the shower, and the water line still has a little hot water in it. The next person goes to shower, and as that hot water is being expelled through the showerhead, it draws up some unheated water that lives in the pipes. Finally the heated water for the second person makes it way through the pipe.

How to fix this:

The only way you can fix the “cold water sandwich” problem is to let the water run a little while to allow the cold water to pass through before the second person gets into the shower.

2. Mineral buildup

RV tankless water heaters are susceptible to mineral buildup. Calcium and magnesium buildup inside your tankless water heater will impair the function of your water heater.

If you have hard water, it’s a much bigger problem than if your water is soft, due to the higher mineral content in the water. Fortunately, tankless water heater manufacturers put a water filter in the tankless water heater so you can check it and clean it on a regular basis.

How to fix this:

You can prevent and fix mineral buildup in your tankless heater by flushing it yearly using a descaler kit like the EZ-Flush Descaler Kit.

3. Overloaded system

You may notice a reduction in hot water flow and volume when you have too many simultaneous demands on your RV tankless hot water heater. This can even lead to the heater shutting down in extreme cases. This is because the heater can only heat a certain volume of water at a time. Any more than that causes problems.

How to fix this:

If you find you just aren’t getting enough hot water flow, or your RV tankless water keeps shutting down, there are three ways to fix it.

First, you should try being sure that not too many silmultaneous demands are being made on your tankless heater. If that’s not possible, you may have to upgrade your system with a second water heater. If that doesn’t work for you, you could try replacing your tankless heater with a larger water heater that can handle the volume of water you need.

4. Error code on display  

Your tankless water heater will display an error code and shut down if the air supply or exhaust is blocked. Assuming the water heater is installed correctly, the problem could be from a wasp nest or a rodent’s nest blocking the exhast or intake. Use a flashlight to thoroughly inspect the water heater vents for a possible blockage.

How to fix this:

Clear any debris from the air intake or exhaust. Then install RV bug screens to prevent it from happening again.

5. No flame

If your tankless water heater isn’t igniting, or if there is no flame, there is a problem with the propane supply. This is most often caused by:

  • The propane cylinder valve not being completely open
  • The propane cylinder being empty
  • Having a leak in your propane sytem

There is also a small chance that there is something wrong with your RV tankless water heater.

How to fix this:

If you aren’t getting a flame on your water heater, start with the easiest thing to check. Make sure your propane cylinder valve is turned all the way open. If it’s open, but you still don’t get a flame, check that you still have propane in the tank and refill it if necessary.

The last thing on our list is checking for a propane leak. Smelling sulfur or rotten eggs is the easiest way to tell if there is a propane leak. However, there are other ways to check for a propane leak.

If you haven’t done so already, consider installing a GasStop propane shut-off device. This easy-to-install device has a built-in propane gauge, so you’ll always know how much propane is in your tank. Not only that, the GasStop device will automatically shut off your propane if there is a potentially dangerous leak. It’s a really easy upgrade that could save you from running out of propane or having a leak.

Track your RV maintenance

Make sure you keep track of all your RV maintenance and repairs with an online tool such as RV LIFE Maintenance. Not only can you keep all of your documents in one place, but you’ll also receive timely reminders when maintenance is due to help you avoid costly repairs and potentially serious accidents.

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