Upgrading your RV to a Tankless Water Heater

About the Author

Tom Davidock

Tom has been working in the outdoor recreation and environmental fields for over 25 years and writing about for the past 15. Whether it's camping, or RVing, Tom provides first-hand kneowldge of the information outdoor enthusiests need to enjoy adventures on the road. Tom has had his content featured in industry-leading news publications including RV Business, RV News, and RV.com. Tom is also the author of "Used RV: The Complete Guide for Buying a Used RV."

Are you looking to upgrade your RV hot water system to an RV tankless water heater? A few short years ago, RV tankless water heaters were more of a luxury if you were willing to pay for one. However, they have recently dropped in price and are finding their way into new RVs as standard appliances. Many RVers consider on-demand water heaters to be one of the best options for their hot water needs.

However, if you have an RV with a traditional water heater, you may be wondering if you could upgrade to an RV tankless water heater. The answer is yes. In fact, If you’re a little handy, you can easily make this upgrade yourself.

What is an RV tankless water Heater?

The name says it all. A tankless RV water heater heats water on-demand rather than heating in a storage tank. Standard RV water heaters usually come in 6 or 10 gallons, holding the water in an insulated tank to heat and make it available for use. Then, when you need hot water, it pulls it from the tank. The downside is that once you use up all of the stored hot water, you need to wait for the entire tank of water to heat up again to have more hot water. In addition, traditional water heaters may have a slow recovery time, meaning that it can take 20-60 minutes to refresh the hot water.

An RV tankless water heater, by comparison, heats the water on demand. There is no storage involved. When you turn on the hot water faucet and call for water, the tankless system will kick in and heat it as you need it, providing an endless hot water supply. For this reason, they’re a great upgrade for a large family that needs unlimited hot water.

RV tankless water heater benefits

RV tankless water heaters are more efficient

Unlike traditional RV water heaters, tankless water heaters will heat the water as needed rather than storing it for future use. As a result, it only consumes fuel, most likely propane, when in use. With a tankless heater, you’ll use less propane to heat your water. With a standard water heater, the entire tank is heated, even if you don’t need it. By heating water instantly, a tankless water heater is much more efficient. They’re a great option for full-time RVers who miss some of the comforts of home.

Endless hot water

One of the main reasons people opt for an RV tankless water heater is to have an endless supply of hot water. With an RV tankless water heater, you never run out of hot water as it heats the water as you use it. With a standard RV water heater, you may have enough water for one or maybe two quick hot showers. With an RV tankless water heater, you can take as many hot showers as needed and never run out of hot water. As long as you have water, you will have access to hot water.

Energy Efficient

Tankless water heaters are usually heated by propane gas. While some electric water heater options are available in a tankless version, they’re not as common. A propane unit will use a direct spark ignition to only fire up the water heater when you request hot water. Because of this, you’re only heating water when using it. While traditional tank systems typically have a good thermal efficiency rating, depending on the power source, you’ll still be using electric power or propane to keep the tank water hot. However, with an on-demand system. You’ll benefit from the unit’s efficiency and realize some energy savings in your propane use or electric bills.

Instant hot water

With a traditional RV water heater, you need to wait for the water to heat up before you have access to it. It can take 20-60 minutes to heat up for use. With an RV tankless water heater, hot water is instantly available and a great choice for large families. When you turn on the hot water tap, tankless water heaters will instantly begin to heat water in the system’s heat exchanger. The amount of hot water is only limited by the unit’s water flow rate and heating capacity. A regular water heater is limited by the small size of the tank.

Lightweight for traveling

When you travel with a traditional water heater, you’re likely holding 6-10 gallons of water in the tank. A gallon of water weighs 8.3 lbs, so a 10-gallons of water will add 80 pounds to your load. Even empty, tanked water heaters can weigh 20 or more pounds. Therefore, RV owners can save upwards of 100 pounds if they have a tankless water heater. In addition, tankless water heaters will typically take up less space than a larger tank water heater. Hot water tanks in traditional water heaters account for the majority of the size of the unit. Tankless versions will feature a much more compact design and often fit in smaller spaces.

Downsides of an RV Tankless Water Heater

More Expensive

While prices have dropped, RV tankless water heaters are still more expensive than traditional water heaters. You may need to have it professionally installed, which can be more costly than a conventional RV water heater. However, some models are only $100-$200 more. If you need a water heater replacement, this may be a good tie to upgrade to consider an RV tankless water heater.

Easy to use more water

This downside isn’t necessarily a negative since you can avoid it, but endless hot water can lead to longer showers and a greater amount of water use. Again, this scenario isn’t an issue if you connect to a full hook-up site. However, if you’re boondocking and relying on your freshwater storage fed by your water pump, you may use more water than you have in the past. 

Must have freeze protection in cold climates

If you camp in freezing or sub-freezing temperatures, tankless water heaters will likely require freeze protection, or they can freeze. Since water passes through small plumbing pipes/fittings, it can freeze quicker than a traditional water heater. You can avoid this situation, but you need to ensure that the model you’re installing has built-in freeze protection. For example, some units have a built-in thermostat, recognizing when temperatures dip below 37 degrees. It will then turn on very briefly to heat the water in the system, preventing freezing. Additionally, on-demand RV water heaters may heat a little slower in cold temperatures because the water supply starts off with cold water.

Choosing an RV tankless water heater

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The most critical decision in deciding on a tankless water heater is to select a suitable unit for your RV. Unlike installing a tankless water heater at home, where you have tons of space to work with, you often have a confined space in your RV. Therefore, you will want to ensure that you purchase a model that will fit into your RV.

Luckily, if you have a traditional 6-gallon Suburban or Atwood unit, several tankless models are available and designed to fit into the same space as the old one. However, if you have a unique setup or are replacing another tankless unit, you will want to make sure that you research your options and find a model that will accommodate your available space. This decision should also include venting since all propane tankless systems will need an external exhaust. One of the most popular upgrade models for this setup is the GIRARD 2GWHAM Tankless Water Heater

Additionally, when choosing the best tankless water heater for your RV, research the water flow rate of the unit. While a traditional 6-gallon water heater will provide a steady flow of water to your kitchen sink faucet or shower, a tankless unit will be limited by its flow rate capacity. If you have too much water entering the unit, and it can’t keep up, you’ll end up with warm water instead of hot water. To ensure that you have plenty of hot water, make sure you correctly size the unit for your needs. Each tankless water heater will list a BTU rating (British Thermal Unit) that will determine how many gallons of hot water it can supply at a time.

On some units, you can also adjust the hot water temperature, so if this is a feature you want, keep that in mind when researching different models. Also, don’t forget about safety features. The best RV tankless water heaters will have advanced safety features like turning off the gas supply if your propane tank runs out and preventing freezing, overheating, and overpressure scenarios.

Installing an RV tankless water heater

While installing many RV tankless water heaters can be done yourself, you must consider how comfortable you are with this type of work. You will need to do some plumbing, electrical work and deal with propane lines. If this is outside your comfort zone, you should contact a professional.

Step 1: Disconnect water, electricity, and propane.

Safety first: turn off your propane supply at the tank, disconnect the power supply to your RV, and turn off your RV pump and outside water hook-up. You don’t want any water pressure flowing to the water heater.

Step 2: Drain the water heater

To drain the water heater, open the pressure relief valve and then open the drain valve to release all of the tank’s water. There will likely be pressure in the tank, so be ready for it to spray out. If your tank isn’t cool, it can cause burns. So always let the tank cool before working on your water heater.

Step 3: Disconnect water heater electric, propane, and water supplies. 

Now is an excellent time to pull out your smartphone and take photos of all of the connections to have a reference for installing the new RV tankless water heater. Then, carefully disconnect everything from your old unit. There are usually two water lines, several electrical connections, and the main propane supply line. Brackets may also secure the unit to the floor or framing.

Step 4: Remove old water heater

Once everything is disconnected, you’re ready to remove the old unit. First, you’ll need to remove all the fasteners holding the water heater to the RV body. Next, you will need a putty knife to cut through any caulking, butyl tape, or other sealants securing the water heater to the RV’s exterior. 

Once removed, give the cavity where the water heater was sitting a good cleaning. Ensure to remove all residual sealants and prep the area for the new unit.

Step 5: Install RV tankless water heater

You should have your RV tankless water heater, and you have already made sure that it is the right fit for your RV. Slide the new water heater into the open cavity and ensure that the new door aligns with your RV and the water heater. Since the new tankless unit may be smaller than your old water heater, you may need to install some framing to hold it in place so it doesn’t move around. In addition, you want to ensure that the new tankless water heater is secured firmly to the RV and won’t move when in use or traveling. 

Step 6: Install frame and door

Secure the new RV tankless water heater frame and door to the RV. Use butyl tape and caulking to properly waterproof the area around the cabinet.

Step 7: Reconnect water, electrical, and gas lines

Reconnect the water lines to the water heater. You may have some extra valves and lines leftover from your previous unit. Bypass lines, which you used for winterizing your water system, are not needed when using an RV tankless water heater.

Step 8: Reconnect the electrical and gas lines. 

This step can be the most challenging part of the job. If you’re not familiar with working on DC electric lines or propane, it may be a good time to contact a professional to make these connections. You can do a lot of the leg work by completing the steps above and save money by paying someone to do this step.

The RV tankless water heaters will use 12V DC power to operate the unit and propane to heat the water. Since the previous propane connection may not line up with the new propane connection, you may need to extend a line or use a flexible propane line. I highly encourage you to assess your ability and do a lot of reading on this part if you choose to do the entire process by yourself. There are some great resources available. Check out the video below.


Upgrading to an RV tankless water heater can be an excellent option for you, depending on your needs and how you like to camp. For example, if you are a heavy water user in your RV, take multiple showers, and do a lot of dishes, you may have realized that a 6-gallon tank water heater isn’t adequate. However, if you haven’t run into any issues and don’t run out of hot water, it may not be worth the expense to upgrade.

While RV tankless water heaters have dropped in price, they’re still more expensive than traditional water heaters. Also, if you have a unique water heater setup, you’ll likely pay more for a tankless system. In addition to the actual cost of the unit, you will also need to consider the cost of installing it. However, if you’re handy and feel comfortable making this upgrade yourself, you can save money on the installation.

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