RV tankless water heater

I have posted often in these forums how satisfied I have been with the Truma Comfort on demand hot water heater. It has NONE of the problems others have commented on including using more propane. My experience with the Truma is that I got instant hot water while I had to wait for 30 minutes to get my 6 gallon hot water heater to completely heat up. I had no water flow issues or fluctuating temps issues when hooked up at a camp ground. The only downside is that it is very expensive.

I see no use for one in a RV. I have one in my house that has brought down my electric bill. My bathroom is the longest run so like the old heater I had both waste water getting hot water to my bathroom. The ideal situation would be to have one IN each bathroom and kitchen but you need some way to avoid a leak at the heater itself and causing a flood. JMO
Don

Agree with SparkDr. No for a RV where you usually try to conserve water. But for our home where you can take the long showers in the morning to 'wake up the old bones/muscles or when family comes for the holidays when you have the unlimited amount of hot water for everyone to take their showers all morning long. Yes it has a place, but not in my RV.

The only way I can see a tankless water heater being useful in an RV is with a recirculating valve, so the water that is used to warm it up is shunted back to the fresh water tank and not wasted.

Instead, I'd probably consider a Truma Combi system as a possible upgrade. It has less water, but heats it quicker. For an upgrade, it may be difficult, but for a new rig, it does the job of both a 20k BTU furnace and a water heater, so wish RV makers would use it, freeing up quite a good amount of cubic feet for storage or other tasks.

Slight hijack of the thread about to happen here, but I need to offer my 2 cents regardless. I run a HVAC, plumbing, and electrical contracting business. We've sold and installed hundreds of tankless water heaters in homes with very few problems. I put one in my own home in 2007 and it has performed flawlessly since day one. Most reported problems are due to one of 5 things: (1) improper system design, (2) improper installation, (3) professional failure to properly educate the end user, (4) poor product offering decision, (5) lack of maintenance. Tankless water heaters are not water savers...they are meant to be turned on and run for a period of time. Most residential models pass up to 0.6 gallons of cold water through the unit before telling the burner to ignite which causes a delay in getting hot water to the tap. For those who use short bursts of hot water (ie: quick rinse of dishes or a military shower), the line is just getting packed with these pockets of cold water which is known as cold water sandwiching. Having said all of that, it's a no-brainer to see why a tankless is a bad idea for RV'ers. We've all been programmed and trained to conserve water by using short bursts whenever possible. A properly designed and installed Rinnai or Rheem tankless in a home is worthy of staking my reputation on. Other brands....not so much. In fact, I won't even install them. But for an RV, no. I don't see tankless as a viable option just yet.

I had a tankless water heater in my home and it was horrible. It never could make up its mind whether to send hot water or not (see variable temperature in 2nd post). We ended up ripping it out and we put a 50 gal standard in. Oh, and we have huge gas lines run to the house and to it, it wasn't a gas issue, and we have 1 1/2" water lines, so it wasn't a water issue (we have amazing water pressure).

IS your current water heater propane OR electric and propane?

IF electric/propane.....operate BOTH heating sources at same time for 'fastest' recovery.


Whether yours is an Atwood or a Suburban Brand changing for 6 gallon to a 10 gallon will require cutting a larger opening (and new framing) in the side of RV.

Atwood...same width but height is 3" difference and needs an extra 2" for depth

Suburban.....roughly 4" H & W difference and at least 1" for depth.


Now if yours is propane only.......direct swap for a 6 gallon combo unit (electric/propane)

Otherwise......wet down/stop water flow---soap up/rinse off ('NAVY' shower----but 4 yrs in NAVY never took one nor do I in my RV :B )

Problem is if you are using Michigan 45F input water, it will only heat a small amount of water to 105F. If you are camped in Florida with 65F or 75F water, then it can heat a lot of water and take a decent shower.

With 45F water, then less than 1 gallon per minute flowrate, as you increase flow, it will get cooler. WWorking from a water pump is even more difficult, say it is to warm, you must increase the flow rate or try to add some cold water. If to warm, you must slow the flow rate, so that the 45F water spends more time in the heater to reach 105F. If you slow the water to slow (on the pump) it will perhaps overheat or the pump will cycle off or something, and you will get cold water for a few seconds.

You are much better off using a regular 6 gallon tank. You could also use a electric option, increasing the BTU input a little bit while plugged in at a campground.

That said, I did buy a L5 tankless water heater. It hooks up to my garden hose, and I used it to warm he water going into my 100 gallon fresh water tank, in the winter. I would have 45 - 50F water, and at best might gget a 3-4 minute shower. By warming the water to 85F, and pumping from the fresh water tank (I have a 5.7 GPM Variable speed pump) I could take a 15 minute shower with the 6 gallon hot water tank.

The L5 is a portable water heater, I hung it from my steel bike rack, next to my fresh water filler. It is 39,000 Btu's per hour. So it can heat 5 liters per minute by about 60F (or 45 - 105F). (1.25 gallons per minute). It was only $120 or so at Amazon.com

They also sell a L10, rated around 60,000 Btu's per hour for about $200. The RV water heaters - I do not know what BTU the tankless is, and if it is variable gas input or not.

The normal 6 gallon tank that I have is 8,800 Btu's per hour. 10 gallon models are closer to 10,000 Btu's per hour. Most will have a 800 watt electric heat option - about 2,800 Btu's per hour. You can run both at the same time when you have the electric option.

Many conserve water while showering by lathering up, then shut off the shower water at the valve in the handle. This allows the heater to warm the water further, while you use the washcloth. Then they rinse. It is a more effective way to shower with less water. So called 'Navy Shower' because fresh water is a limited while out at sea. It also conserves space in the grey tanks too.

While dry camping, I normally will transfer some shower water from my tub into the nearby toilet. This is because for whatever reason, I have a 42 gallon grey tank and 59 gallon black tank. Fresh is 100 gallons. I use a dishpan that is almost as wide as my tub, and I can quickly transfer all but 1" of the water in 3 scoops. Or with just a shower pan, standing in a dishpan you might collect say 1/4 the water?

Also if you do dishes in a dishpan, you can toss that out on the grass, just like all the tent campers do.

Have fun camping!

Fred.

That's helpful. Seems we need to better understand how shower. Thank you all

P

Im a plumber 30 years.. I would never install a tanless in my home let alone an RV.

#1 if you are always on full hook ups may be the only time I recommend them if you truely want to stay in the shower forever, but the drawbacks outweight any benefit.

#2 You need 1 gpm to operate the flow control. Boon docking when I do dishes I often trickle the HW. Tankless will never work. Additionally I have low flow aerators at 1 gpm. Tankless may activate or may not.

#3 waste more water, does not save as they say. Why? need to turn on full blast HW to activate flow control. Cannot deviate or unit may turn off.

#3 temp control is simply low. med, high flame dial.. Its will not auto adjust

#4 They say saves propane,, This is nonsense as The burner in attwoods is 50k btu;s. The girards are 18-36K. The tank heaters are a mere 10k btu. ( Do the math)

I for one only heat the water when we need it. Tank usually stays hot for what I need to do. If showering we take back to back showers with 15-20 minutes in between. I leave switch off most of the time. Once I heat a tank of water we can use that all day for waht we do. Ill heat the tank at night before bed and first thing in morning.

#5 Will eat up 12 volt power. These units have blowers. If I was boondocking thats the last thing I would want is another 12volt motor to eat my amps.

#6 gas line to original heater may need to be up sized due to #5 above. If the line is only sized to supply 15k btu say, then on high fire the unit will starve for LP.. Sooting and CO issues can develop... LP is higher pressure though. This is a mathematical equation that will need to be calculated...

Although at 11" W.C. this is usually not an issue but pressures need to be checked with all other gas appliances running 100%

All my opinion..

I would install a 10 gallon heater or just take shorter showers.

I have never had an issue of taking 10 minute plus showers on full hook ups and just sensing some loss of HW

Just my 2 cents... : )