How we learned to love our tankless water heater
Tankless water heaters are becoming increasingly more commonly installed in all RVs, including modern AIrstreams- and not everyone likes them, preferring the older 6 gallon tank heaters instead. And while there are pros and cons to both systems, once we figured out a simple solution that solved the most aggravating cons of the tankless system we would never switch to a tank system again.
Tess originally came with a tank system, but it was fairly rusted out so we never even tested it. We “knew” we wanted to go tankless, even though we’d read about some of the disadvantages they had, and we forged ahead and bought the Fogatti RV Tankless Water Heater. It was pretty easy to install, but we knew we didn’t want to use the modern plastic door it was supplied with so I just modified the original water heater exhaust panel. I didn’t take any pictures of the modifications but it was pretty straightforward- I extended the exhaust pipe of the new water heater to extend past the camper wall and into the original heater exhaust. I had to cut a new hole in the original exhaust cover but you can’t see that from outside.
Once the unit was installed and we started living with it, we realized some of it’s flaws. The basic premise of a tankless heater is that the propane only turns on if there is water flowing through it at volume- a low flow of water won’t ignite the heater. So you set the water temperature you like on the controller, turn the water on full blast and once a quart or so of water flows through the heater it ignites the gas and it heats up the water just fine, and as much as you want. This works great where you have full hookups- both water and sewer. If you don’t have full hookups, or if you are boondocking, there are a couple serious flaws.
First flaw- the water has to flow for the heater to ignite the propane and then it takes about 30-45 seconds for the water to come up to temperature, flow through the pipes and then finally come out of the shower warm enough to get into. Depending on how far away your shower is the amount of water used can be a lot- for us it was about 1/2 gallon. Since we only have about 25 gallons of fresh water and 26 gallons of gray water, that’s a pretty substantial loss of fresh, and fills up the gray tank that much quicker.
“But wait”, you think, “I’ll take a navy shower and turn it off while soaping up and save water that way.” An excellent idea…but no. And that brings up the second flaw. Remember how the heater requires water flow to stay ignited? Well as soon as the water stops, so does the propane. And while that keeps the unit from overheating, what it also does is start the process over. So you’ve soaped up and are ready to rinse and turn the water back on…at first the water is still warm because that was what was left in the pipes. But the heater required another 1/2 gallon of water flow before it ignites and all that unheated water has to come out- and it does, all on your soapy naked self! In the summer it’s not too bad, in the winter it is damned cold! This gives you a cold water “donut” warm on both sides, but cold in the middle. So you either suffer the cold or step out of the water stream until it gets warm again, and you lose another 1/2 gallon of fresh water and add another 1/2 gallon to your gray tank for nothing. Two people showering once a day and you reach capacity pretty fast.
The simple solution for us was to install a diverter valve and another pex pipe that goes from the showerhead back to the freshwater tank and joins in with the fill tube of the tank. Since the water is clean it has no effect on the watertank water quality. If we are boondocking it is saving the fresh water, and if we are on city water it saves us from adding to the gray tank- it does fill up the fresh tank but we can either use that later or drain it out. It was a bit of a pain to run the additional pex line from the back of the camper up to the front but not that bad- though it would have been easier had we done it when we ran the first line!
We thought about doing the same with the kitchen sink, but since both faucets would tie to the same “return to fresh tank” pex pipe we’d have to make sure the diverter valve on the shower was closed or else diverting the kitchen faucet would send the cold water out of the shower instead of back to the tank…since the shower diverter is in line AFTER the shower faucet there would nothing to prevent water from kitchen from going out at the easiest exit- in this case the showerhead. So we get around this by turning on the shower with the diverter sending the water back to the fresh water tank and once it gets hot, turning on the kitchen faucet. It’s an annoyance, but it works, and the distance from the shower line to the kitchen line is only a loss of about a cup of water.
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