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

What Are the Differences Between Tank and Tankless Water Heaters

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

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.

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.

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.

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

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.

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

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.

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.

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.

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

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.

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

Seating the new heater

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

Electrical accessories

Finishing up

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

Wrapping Up: Your Tankless Conversion in Summary