Step-by-Step Instructions On How To Convert RV Water Heater To Tankless

tankless water heater

How to convert an RV water heater to tankless is an interesting prospect that begs closer examination. For the most part, what sets RV camping apart from, say, a tent in the woods are the home comforts. And having a ready supply of hot water must figure as one of the most desirable of those comforts.

Enter the tankless water heater with unlimited hot water at your fingertips.

What Are the Differences Between Tank and Tankless Water Heaters

Let's take a look at what sets tanked and tankless RV water heaters apart.

Tank water heaters

Essentially, a tank water heater is both a water heater and a hot water storage device. The tank fills with water and heats it to a pre-set temperature with propane or an electric element. A thermostat then keeps the water at that temperature as long as the RV is in use.

Tankless or instantaneous water heaters

A tankless water heater also produces hot water using propane or electric power. However, that's where the similarities end. In essence, tankless water heaters are on-demand devices, which means they heat water only when the hot water system is in use.

This is a relatively simple process that employs a flow valve to control propane or electric heating elements in the water heater. The cold water supply runs through the elements and heats in passing. The flow valve only switches the heaters on when a hot water outlet opens, and water flows through the system.


What Are The Benefits Of A Tankless Water Heater

In case you're still wondering, tankless water heaters have many benefits.

  • Convenience

The average RV tank water heater holds around 10 gallons or less. That isn't much when you're trying to get a family showered, as well as washing dishes, for example. And that brings us back to the question of how to convert an RV water heater to tankless.

Tankless water heaters, on the other hand, deliver as much hot water as you need whenever you need it. As long as you have cold water and a propane or electric power supply, you're good to go.

  • Efficiency

Tankless water heaters are also more efficient than their tanked siblings. As they don't have to maintain the temperature of the tank water continually, they typically use less propane or electricity. We aren't talking massive savings here, but any savings benefits you.


​How to Convert an RV Water Heater to Tankless: Points to Consider


Before we dive in and start talking about how to convert an RV water heater to tankless, please carefully consider the following points.


Learning how to convert an RV water heater to tankless is a complex project. If you have good technical insight, experience, and tool sense, you can make it a reasonable DIY project. However, if you feel at all uncomfortable about any part of the process, let a professional install the heater.


Your safety and that of your family is of paramount importance. Always ensure that you follow safe practices regarding disconnecting and re-connecting electrical and propane supplies. Again, if you are unsure, seek professional assistance.


​How to Convert an RV Water Heater to Tankless: The Big Picture


The basics of the project involve first draining the water tank then disconnecting the old heater from all service supply lines. These would typically be both hot and cold water lines, the electrical supply and, of course, the propane lines.


Once you've done that, you can clear the exterior flange of the old heater of all weatherproof sealant. You may then remove all mounting fasteners, pry the mounting flange loose, and slide the old unit out of its recess. All that remains is to clean the area, slide the new heater into place, and re-connect the service lines.


Choosing A Suitable Tankless Heater

This is probably the most important part of the project if you want a smooth, hassle-free installation. Fortunately, most RV water heaters adhere to basic standards regarding dimensions and fittings. All you need to do is take your time to make a sound choice from the get-go.


Obviously, one has to have a good idea of what the new heater's hot water output would need to be. Based on those specifications, you can go ahead and start shopping.

sample of a tankless water heater

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Dimensions

The first step is choosing a suitably rated heater that is as close as possible to a straight drop-in replacement. This isn't too much of an issue, as most new tankless heaters are listed as a direct replacement for specific models. If you're not sure, consult a sales representative or installation technician for advice.

Venting

During this part of the process, you should pay specific attention to the position of the heater's venting system. Your choice of tankless heater should vent in the same position as your existing heater. This will prevent you from having to make any expensive and time-consuming structural modifications to your RV.

Fittings compatibility

The second important consideration would be compatibility with the existing water and propane connections. Incompatible fittings are often a cause of delays and extra expenditure when converting heaters. That said, there is a wide range of adaptors available. Just make sure you cover these bases before proceeding.


​What You Will Need to Get It Done


repair tools

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Considering the complexity of how to convert an RV water heater to tankless, you don't need too many tools or equipment. A basic set of hand tools, including a couple of adjustable wrenches, screws, screwdrivers, pliers, hammer, and chisel, should suffice. A cordless battery drill with a set of screwdriver bits is a convenient, time-saving tool.


A couple of rags to dry up water spills or clean off excess sealant will come in handy. A good solvent cleaner and a caulking sealer applicator will also be required. A roll of electrical insulation tape and some PTFE thread sealing tape would also be useful additions to the arsenal.


Getting It Done: Removing The Old Tank

Once you have all your tools and equipment lined up and your new heater has been unpacked, you can get started.

Safety first

The first step in the process is isolating all electrical, water, and propane supplies to the old heater. Make sure you get this right and that all other folks involved know not to switch anything on while you're busy.

Draining the tank

The next step is to drain the old water tank. Before you do, make sure the outflow of water isn't going to damage anything or cause electrical shorts. Now, locate the drain valve. Open it and give the tank time to drain completely.

Disconnecting your supplies

Once the old heater tank is empty, you can start to disconnect the unit from all supplies. Double-check that everything is still isolated, then disconnect the electrical supply from the old heater. You should either mark the wires or take a photo to make sure the reconnection goes smoothly.


The next step is removing the hot and cold water lines from the rear of the old heater. Again, if they are not clearly color-coded, mark them. And you should keep a small box handy to put all loose fittings in one place.


The last disconnection step is the propane supply to the old tank. When you have removed the propane line, wrap a rag or a plastic bag around the open end of the fitting. This will prevent dust, water, or gunk from getting into the propane line.

Removing the old tank

Once you're sure that all supply lines are disconnected, you can go outside to remove the old heater. Just a word of caution -- make sure none of the water lines, electrical cables, or propane line snag on the heater. You will remove the tank from the outside. A not-so-visible snagged line could cause havoc.


Start the removal process by taking all the mounting fasteners out using that cordless battery drill. Remember to keep the screws or bolts all together in that box! When you remove all fasteners, you can use the chisel and hammer to gently pry the mounting flange off the side of the RV.


The flange will almost certainly have a lot of sealant around it and may take some coaxing to free. Take your time with this and try not to damage the flange or the side of the RV. Once you have removed the flange, you'll be able to slide the old water heater out of its recess.


Keep all the old fittings, screws, and flange in a safe place with the old heater. If anything should go wrong with the installation of the new unit, you can always reinstall the old one.


Getting It Done: Installing The New Heater

OK, let's jump in and get that new tankless heater installed.

Preparation

Before you get busy with installing your brand new tankless heater, a bit of preparation is called for. To ensure the new heater flange will seal correctly, you'll need to clean off all of the old sealant. Use your chisel or a paint scraper to do this, making sure you don't damage the RV surface.

You'll also want to use your solvent cleaner to get the flange area clean before proceeding. This will ensure that the new sealant bonds to the RV surface correctly.

Installation

This is an excellent time to make a cup of coffee, sit down, and think through the installation process. A quick dry-install will show if any modification needs to be done to fit the new heater. If this is the case, assemble all the required materials and tools. Once you're comfortable that all is correct, present, and in place, you're good to go.

Setting up

It's wise to do as much of the work as is possible while the new heater is still outside the RV. This includes putting PTFE tape on fittings or installing adaptors and wiring extensions if required. This will save a lot of sweating and cussing later because once the new unit is installed, you'll usually work through a small, cramped hatch.

Seating the new heater

Now, you need to do the rest of the installation in a slow, methodical manner. Don't rush things at this point; take your time and get it right the first time.


The next step would be sliding the new heater unit into the recess, making sure it doesn't hang-up or snag on anything. Seat the unit completely and check that it sits flush and level. If all is good, pull the unit out slightly, so it balances securely with enough room to seal the flange.

At this point, you can make any tricky electrical connections from the inside of the RV. With that done, you can apply putty tape to the flange area of the recess and seat the unit. Take time now to check whether the new unit's mounting holes line up and drill any new holes if required.


You can install one or two mounting screws at this point — just don't torque them all the way up yet. Now, you're ready to make the internal connections to hook up the new heater to the service lines.

Reconnecting

If you've taken the time to set up correctly, this part of the process shouldn't pose any problems. There are, however, a couple of considerations when reconnecting your water and propane lines.


The first point is ensuring you connect the correct water lines to the appropriate points on the heater. The second is taking care not to cross-thread any of the fittings, as they can be quite finicky.


Lastly, don't over-torque any of the fittings, as it is really easy to break the fittings off the heater. The best way to prevent this is to use a second wrench to hold the tank fitting while you secure the hose fitting. A critical point right now is double-checking your propane line is securely connected.

Electrical accessories

Most tankless water heaters have a temperature control switch that needs to be mounted near the heater. This generally involves cutting or drilling a hole in an adjacent panel to allow the wiring to reach the unit. Connecting the switch is usually straightforward, with instructions typically included with the heater.

Finishing up

When all the internal connections have been made, you can install all the screws on the outside flange. If you're using a silicone sealer instead of putty tape to seal the unit, now's the time to apply it. Once all the screws have been tightened, you can trim or wipe off excess tape or sealer.


When the unit is secure, you can attach any vent fittings and put the door or cover onto the heater. At this point, you're just about done, and you can commission your new tankless water heater.

Finishing touches and commissioning the new heater

All that remains is a tidy up and a final inspection before running the heater for the first time. Use this time to tidy up the wiring and clean up any dust, debris, or water in the heater cabinet. Then, grab another coffee and run a mental checklist of all the critical points of the installation.

If you're happy with the job, it's time to commission your endless hot water supply. This is where a second set of hands comes in handy. Get someone else to turn the water supply back on while you keep a close eye on the connections.

If there are no leaks, you can grab a dish of soapy water to check the propane connection. To do this, turn the propane supply on and brush soapy water around the fitting. If you see no bubbles forming around the fitting, then all is good.

All that remains now is to turn the hot water outlets on, check the water flow, and adjust the temperature. And, of course, race the rest of the clan to see who gets the first long, hot shower!


Additional Reference Material

So, now that we have considered how to convert an RV water heater to tankless, let's look at keeping it running smoothly. These books lend some interesting insights into the correct use and maintenance of RV appliances, including water heaters.


Wrapping Up: Your Tankless Conversion in Summary

water coming out of the shower

Image Source: Pixabay.com

We hope that this article has lent some useful insights into the often daunting task of how to convert an RV water heater to tankless. Unfortunately, there are so many different types of heaters and installation realities that it is impossible to cover everything in a single article.


Just remember, there are no brownie points in not asking for help. If you are wondering how to convert an RV water heater to tankless and are not sure of how to go about it, ask. There are many great resources and folks ready to help out there that you are sure to get the assistance you need.


If you have ever wondered how to convert an RV water heater to tankless or have any advice or suggestions on the subject, please feel free to use the comments section below.

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