Hot Water Replacement

[Fire19]

I need to replace my 20 year old water heater in my Fifth Wheel. I am wondering if the On-Demand heaters are a good choice? I currently have a suburban 6 Gallon SW DE. or it just better to stick with the Tank water heaters ?

Thanks

[wa8yxm]

Fire19 wrote:
I need to replace my 20 year old water heater in my Fifth Wheel. I am wondering if the On-Demand heaters are a good choice? I currently have a suburban 6 Gallon SW DE. or it just better to stick with the Tank water heaters ?

Thanks

That... is a good question.. So here are some talking points.

ON-Demand RV heaters are Propane only because you don't have the Wattage to heat water that fast.

And if you sometimes camp in cold weather.. Since they do not heat without flow... Well that can cause an issue (If I were making one for RV use I'd offer a optional "Do not allow to freeze" heater.. lower wattage. (perhaps 100 electric or alt propane) set to say 40 degrees)

And though I tended to follow warm weather... i got bit by sub freezing a few times... (like 3) the 3rd time I learned how to spend no money (Though a PEX line did freeze.. in the middle of an 8 foot run. the fittings on the ends (Which do not freeze well) were protected so total damage was $0.00)

[Gdetrailer]

wildtoad wrote:
I’ve never understood how a small OD wh can provide adequately (subjective I know) hot water for a high flow requirements of a shower, especially during the colder months.

With modern day water standards there is no such thing as a "high flow" shower.. 1.5 to 2.5 GPM is pretty much the water flow standard unless you have done something to modify the shower head for full flow..

FLOW RATES

"Flow Rate Restrictions

Since 1994, federal regulations have limited shower head manufacturers to a maximum flow rate of 2.5 gallons per minute (gpm). California has enacted its own legislation limiting the flow rate to 2.0, which will be reduced even further, to 1.8 gpm, in July 2018. Water flow regulations save billions of gallons of water each year while the latest technologies help preserve or even enhance your shower experience. There’s no need to suffer a substandard showering experience just because of regulations.

The engineers at Delta Faucet believe that environmentally friendly design shouldn’t compromise optimal performance. Before the restrictions, shower heads typically used 5.5 gpm. Restricting the flow to 2.5 gpm led to a new generation of water-saving shower heads. The change in flow rate is particularly noticeable if you go from a shower head produced before 1994 to a modern model. With consumer satisfaction in mind and knowing how important a good showering experience is to customers, the Delta Faucet engineers got to work."

2.5 GPM is nothing, my water well at 45 PSI supplies 11 GPM but the restrictive regulations the shower and faucet manufacturers must follow prevents my shower head from supplying more than 2 GPM at 45 PSI.. Perhaps at 60 PSI (city water pressures) I might get 2.5 GPM.. I would not call 2.5GPM or less to be "high flow" by any means.

[valhalla360]

ernie1 wrote:
I've had a Truma od water heater in my 2018 rv for four years and have had zero problems with it and plenty of continuous very hot water. Certainly hot enough to be super uncomfortable and maybe cause an injury. Dunno about others but am I just lucky?

What weather conditions are you using it under?

If the average temp is in the 80's, your fresh water tank is likely feeding it water in the 80's, so it only needs to raise the temp by around 25 degrees to feel hot.

If you camp in cooler weather, the fresh water tank may be feeding it 40-60f temp water and it will have to raise the temp by 45-65 degrees to get the same temp.

[dougrainer]

ernie1 wrote:
I've had a Truma od water heater in my 2018 rv for four years and have had zero problems with it and plenty of continuous very hot water. Certainly hot enough to be super uncomfortable and maybe cause an injury. Dunno about others but am I just lucky?

Truma is a higher line of On Demand(Germany) and has a better track record. Truma replacement would require running the control communication cable to a spot inside for the wall mount control. Truma's also require once a year decalcification, kind of a pain to do, just time consuming, not hard. Doug

[Gdetrailer]

ernie1 wrote:
I've had a Truma od water heater in my 2018 rv for four years and have had zero problems with it and plenty of continuous very hot water. Certainly hot enough to be super uncomfortable and maybe cause an injury. Dunno about others but am I just lucky?

A lot has to do with the starting water temp, how fast the water is flowing and how many BTUs of heat energy the burner can supply.

In temperate places you might start out with water temps above say 80F+ and at those temps takes no time and not all that much heat energy to raise the temp to say 120F at only 1 or 2 GPM..

Now in colder climates you might be starting with water temps of say 50F and now it takes a lot of heat energy to raise to the same 120F and to get there you might have to have the water at .5GPM which may or may not trigger the burner on or may result in burner on/off/on/off cycles..

ODs do have an hidden enemy, dissolved minerals in the water, the high temps of the flame causes the minerals to fall out of the water and were they fall is in the tubes of the unit which eventually leads to mineral clogs if you do not do periodic de mineral maintenance. Untreated well water tends to have much higher mineral content than say highly processed city water.. Therefore, city water is preferred for ODs but even then some maintenance should be done on a regular basis..

I was going to replace my sticks and bricks tank water heater once after having multiple tank failures.. Discussed the idea of switching the house to a OD with a plumber.. Even the plumber told me that I was better off sticking with a tank water heater.. And no, I was not buying from or needing the plumber, was trying to get the scoop before committing a huge chunk of money on a project that was destined to fail..

My water is supplied by my own well, has an extreme high mineral content and that is after a large water softener.. The water temp out of the well is 50F yr round.. Would have to replumb 20ft of gas line to 3/4" in order to supply enough BTUs in gas to the water heater.. Three strikes..

[ernie1]

I've had a Truma od water heater in my 2018 rv for four years and have had zero problems with it and plenty of continuous very hot water. Certainly hot enough to be super uncomfortable and maybe cause an injury. Dunno about others but am I just lucky?

[wd]

I have an on demand. You waste too much water waiting for the hot water to come and get surges of cold water.

[Lantley]

On demand is a bad idea for RV use. Stick with a tank LP/ electric heater

[wildtoad]

I’ve never understood how a small OD wh can provide adequately (subjective I know) hot water for a high flow requirements of a shower, especially during the colder months.

[valhalla360]

Had a propane one on our boat years ago. We would use 3-4 gallons getting the temp to settle in...then any slight adjustment and you got scalded or iced.

Electric has the problem of providing enough power. A 30amp outlet can provide 2880w continuously (limited to 80% of rating) but that's for everything in the RV. 1200-1500w won't get 40F water up to 110-120F at any reasonable flow rate.

[Second_Chance]

Since Grand Design started putting OD water heaters in some of their units (the Solitudes and Momentum fifth wheels still have 12-gallon standard WHs), there have been many, many posts about problems with them over on the (older) GD forum. There are the problems that dougrainer mentioned plus: 1) without the option to use electric, they go through propane rapidly, and 2) the Furrion units are not insulated and are notorious for freezing and cracking the coils when the outside temps drop or the units are not properly winterized. I would never install one.

Rob

[dougrainer]

I have been an RV tech for 43 years. I would NEVER have a LP powered On Demand Water heater. The On Demands are too finicky and rarely give the higher temps that a lot of people want and like. I have over the years replaced On Demand Water Heaters under warranty with regular water heaters because the customer demanded it and the OEM's agreed to pay for replacement. I have also replaced for Customer pay when out of warranty. Doug

[Grit_dog]

On demand maybe if you're always plugged in to shore power. Otherwise, doesn't seem like the best choice for a mobile RV.