RV Repair Manual
  for the RV Do-It-Yourselfer


Get in Hot Water by Going Tankless in Your RV

By Mark Corgan

There are some options to help your factory water heater improve heating recovery time. You can install what's called a hot rod, which is a electric heating element that replaces the anode rod in your water heater. This rod uses 400 watts of AC power to heat the element and assists the gas portion of the heater with recovery. This is a somewhat viable option for extending your hot water supply time but some water heater manufacturers frown on their usage, stating that it may void the warranty because the lightning rod no longer provides the corrosion protection the standard anode rod does. You still won't get the hot shower of your dreams with this option though.

Here is where the tankless water heater comes in to play. There are two types of tankless water heaters: electric and gas-fired. The first kind works similarly to the hot rod in that an electric heating element heats the water. But that is where their similarities end. Rather than fill up a tank full of water and then heat it, the the electric tankless heater senses water flowing through it, activates the electric heating circuit, and the water is heated instantly. It is 100% automated. As soon you turn off the water flow, the heater turns off. Water temperature is regulated with water pressure. Less water pressure means more heat, and more water pressure equals less heat.

The gas-fired type works very much the same as the electric heater in terms of sensing water flow and instantly heating it. But in this case, a propane burner heats the water. And there are no large electrical power demands needed as with the electric heater. Both can deliver a steady flow of hot water nearly indefinitely, but the gas-fired type will be able to keep up with demand better, and is more easily adapted within a typical RV environment.

The easiest way to mod your RV with a tankless water heater and get that sensational endless shower is to use an inline device that replaces the shower head. This type of heater uses a powerful electric heating element to instantly heat the incoming water just before it exits the shower head. It can increase water temperature by as much as 50F at a one gallon per minute flow rate. This should be enough to supplement the factory water heater so while it's recovering, you are still getting reasonably hot water. The only con is that the unit consumes a lot of current, upwards of 20+ amps. You will need to dedicate a circuit breaker and receptacle for this unit should you decide to go this route.

If you're boondocking, or otherwise camping without hookups, then consider doing this mod with a custom installed gas-fired tankless water heater. These units do an excellent job at providing instant and sustained hot water, and can be used to supplement or completely replace the standard RV water heater. There are a couple of very important things to consider before doing the mod though. The first is the venting requirements. Like your RVs heater, the tankless heater emits CO2 when the burner is on, and the CO2 needs to be vented outside the RV. Three inch tubing is a minimum and should be exhausted through the roof or side wall with the appropriate tubing and vent cap.

You need to also consider where the unit is mounted. The area should be free from anything that could come in to contact with the unit. Also, the unit should have some ventilation or fresh air supply. This isn't critical but the burner does need oxygen to work. Most standard RV cabinet doors don't seal very well to begin with so there should be enough air supply to provide proper performance when the unit is mounted in areas like this. In any case, follow the manufacturer's recommended installation procedures if you are at all unsure. This includes connecting the gas and water supply, and any electrical requirements necessary to power the unit's circuit board.

Finally, and of course the most expensive of all the options, is to completely replace the factory water heater with a drop in replacement tankless heater made specifically for RVs, the RV500. This is by far the easiest way to have endless hot water. Replacing the standard water heater with the RV500 is surprisingly simple. Start by turning off the propane and draining your water heater. Remove the gas supply line and water lines. And disconnect any electrical wiring. Unscrew the fastening screws on the outside frame of the heater and the unit should slide right out.

To install the RV500, reverse the steps used to remove the factory water heater. Chances are the gas supply pipe and the water inlet and outlet tubing won't require any modifications and will attach directly. The heater does require a 12-volt power supply in order for the circuit board to function and otherwise control the unit. It's very low current so you should be able to tap in to most any 12-volt source nearby. Once installed, you just have to turn on any hot water faucet and the unit will automatically turn on. Turning off the hot water faucet in turn shuts off the heater. It's quiet and will keep up with any demand. Now you can take your time showering but you might have to mod your RV with larger holding tanks!

Copyright 2009 by Mark Corgan, owner of ModMyRV.com

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