Pros and Cons of Tankless water heaters in RV

[NamMedevac_70]

Thank you for your replies if any.

[PA12DRVR]

I have a tankless system at both of my remote properties in AK: served by well and / or rainwater catchment. Temperature of the supply water can run between 35 and probably 60. One of the tankless heaters has an electronically adjustable water temp, the other requires a manual plug-n-play to change the delivered water temp.

If one wants to do a lot of shutting off and restarting during use, this is not the system to have. If one has a limited supply of water, this is not the system to have.

However, if there is not a significant limit on water, I believe tankless are actually more cost-efficient (considering cost of gas and electricity) than keeping a 20 gallon or larger tank full of hot water. 6 - 10 gallon? IDK.

All that being said, we use our tankless heaters without the "way too hot or way too cold problem" (IMO, that's a mixing valve issue at the point of delivery) and without any problem with cold intervals...but when we shower with the tankless heaters, we let the water run for about 2-3 minutes before getting in and we keep it going until through with the shower. Similar exercise if we're using how water for other tasks. We have not had problems in either location where the tankless heater is fed by varying volume / pressure of water (i.e. both our locations are served by pumps, either from the well or from the rainwater basin).

Might not be the best application for a typical RV, but there could be some benefits for some situations.

[Rick_Jay]

We have a tankless water heater in our sticks and brick house. It's OK, you do have to change your showering style a bit. Most of us adapted, wifey curses at it every time. And it's been about 8 years so far. I've told her to turn the shower on for about 15 seconds BEFORE she steps into it, but she views that as wasting water. Soooo....she curses instead. And she likes to shut the water off (like in the RV shower) while she's soaping up, Sooooo she curses again when she turns the water back on. LOL Anyway, In NO WAY does a tankless unit save water. It definitely uses more water.

Ditto what folks said about stopping and restarting the flow, as many of us do in an RV shower. Do that with a tankless water heater and there WILL BE fluctuations, hot & cold, in the delivered water temperature until the system stabilizes. At home, the water flow remains constant.

We have a 10 gallon electric/propane water heater unit in our RV and it has NEVER let us lacking for hot water. Even with 5 of us camping in temperatures down into the 20's. When we all took showers, I did kick on the propane WITH the electric element to keep up with demand, but I don't know if I had to do that or not. I just did it as a precaution. BUT, everyone in the family knows how to take save water in an RV shower, but shutting off the flow.

For an RV, water is a precious commodity for some of the camping we do, so no way would I want a tankless unit. The next precious commodity is propane, so having to use propane to heat water when I could be using electric is a con as well. And in a pinch, IF I run out of propane, I could always start the generator to heat the water. (I know, not efficient, but it IS an option. And I've done that while travelling because the generator is running anyway and then when we arrive at our destination, we'll have hot water.)

On a full-hook up site, these issues would be minimized, but we don't always camp that way. You still have to deal with the temperature fluctuations.

~Rick

[Gdetrailer]

valhalla360 wrote:


You don't need much 135F water to mix into 90F tank water to get to 110F at the shower head. That means a 6-10gal water heater can easily provide 30-60gal of hot water. Of course when in Florida with 90F temps, I generally don't feel the need for a really hot shower. In fact just running the cold water which will be around 90F is fine. (Even down around 80F, it won't bother us much).

When camping in 30-40F, that's when a piping hot shower at 110-115F feels really good but now you are asking the hot water heater to bring the water temp up by 80-90 degrees. A tank based heater will be limited in duration but it can get the water up to temperature. Most of the smaller tankless units struggle to get the water that hot on a consistent basis.

Correct!

RV tankless water heater manufacturers do not publish the full specs unlike tankless water heaters designed for sticks and bricks.

Sticks and bricks tankless water heaters typically are able to maintain 45F rise in the temp over the incoming water temp at the rated flow rate often up to 5 GPM.

Incoming water temp of 45F plus 45F rise at 1 GPM for a RV tankless giving you 90F water is going to be a pretty chilly shower.

Sticks and bricks tankless water heaters also feature a much higher BTU burner, often 160,000 BTU compared to RV tankless of 40,000 BTU to 60,000 BTU which is going to limit a RV tankless water heaters useful operating range.

[valhalla360]

wanderingaimlessly wrote:

CavemanCharlie wrote:

wra wrote:

wanderingaimlessly wrote:
Your in florida, for home or rv use you only need to heat the water 30-40 degrees to get the temp you want, from an rv tank you may not need even that much, but as temperature range changes increase, the difficulties regulating it do as well.

I have used changing water pressure less than 20 lbs to 60 lbs (a well pump system) with no problem regulating water temperature.

The main point is to have only the hot water faucet turned on. Having he hot and cold water turned on provides a path for cold water to the shower head, and causes the tankless heater to have less water go through it. That situation causes the tankless heating unit to turn off prematurely, and cold water continue to flow.(burr!) The tankless heater should be set to the desired shower head water temperature. Let it do its job.

So it sounds like in a home that it's a learning curve. Most people don't want to change their habits and don't want to learn new things.

That being said, it also sounds like it might not work as well in a RV where the parameters of flow usage and other things can change.

AND AGAIN, you are in Fl. ground water from a municipal system will typically be near 60 degrees when it enters the home. Well systems are often even warmer because the reservoir tank is in a garage or other heated area.
And in an RV, if it is coming from a holding tank, it may be 80 degrees, but, take that same RV to an area with an ambient temp in the 30's or 40's, and everything changes. The water going through the heater has to go much slower to be warmed the extra 30-40 degrees. Meaning your flow has to become nearly nothing or you live with lukewarm (at best) water.

You don't need much 135F water to mix into 90F tank water to get to 110F at the shower head. That means a 6-10gal water heater can easily provide 30-60gal of hot water. Of course when in Florida with 90F temps, I generally don't feel the need for a really hot shower. In fact just running the cold water which will be around 90F is fine. (Even down around 80F, it won't bother us much).

When camping in 30-40F, that's when a piping hot shower at 110-115F feels really good but now you are asking the hot water heater to bring the water temp up by 80-90 degrees. A tank based heater will be limited in duration but it can get the water up to temperature. Most of the smaller tankless units struggle to get the water that hot on a consistent basis.

[valhalla360]

kedanie wrote:
From someone who actually has a tankless water heater, don’t give much credibility to those that run them down while never having one.

We have been running ours now for over 5 years and it works very good. Over the long haul we have found that it actually uses less propane than a tank style. Yes, they don’t have a electric option. When in low flow areas, just turn on your pump and all is fine. When dry camping, we use a pan to catch the cold water while waiting for hot and use it for toilet flushing. That cold water is typically less that a half gallon. Don’t forget, tank style heaters have cold water in the lines also.

Don’t run something down when you have never tried one. That is just fear mongering.

Keith

We've lived with one for 9yrs...we largely lived without hot water as it was more hassle than it was worth.

[frankwp]

Most of our camping involves 7 people in our fifth wheel, 4 adults & 3 teenagers. We have a 10 gallon HWT & running out of hot water is not a problem.

The cons are:
- you can't use the campground power to heat the water
- goofy temperature regulation issues
- initial cost
- cost to run it
- maintenance & repairs
The pros are:
- there are none that would apply to our situation

[MRC54]

as usual, for most any topic, YMMV

We are new full timers. 41' Alpine. Mostly hooked up in our first 3 months. We love our Suburban tankless. My experience with other Class A (three of them in the 2000s) was that having limited hot water via a tank was inconvenient. We are fortunate to have a large shower in our 3712KB, and tankless allows a nice long shower, followed by DW's long hot shower.

Again.... YMMV

[wanderingaimles]

CavemanCharlie wrote:

wra wrote:

wanderingaimlessly wrote:
Your in florida, for home or rv use you only need to heat the water 30-40 degrees to get the temp you want, from an rv tank you may not need even that much, but as temperature range changes increase, the difficulties regulating it do as well.

I have used changing water pressure less than 20 lbs to 60 lbs (a well pump system) with no problem regulating water temperature.

The main point is to have only the hot water faucet turned on. Having he hot and cold water turned on provides a path for cold water to the shower head, and causes the tankless heater to have less water go through it. That situation causes the tankless heating unit to turn off prematurely, and cold water continue to flow.(burr!) The tankless heater should be set to the desired shower head water temperature. Let it do its job.

So it sounds like in a home that it's a learning curve. Most people don't want to change their habits and don't want to learn new things.

That being said, it also sounds like it might not work as well in a RV where the parameters of flow usage and other things can change.

AND AGAIN, you are in Fl. ground water from a municipal system will typically be near 60 degrees when it enters the home. Well systems are often even warmer because the reservoir tank is in a garage or other heated area.
And in an RV, if it is coming from a holding tank, it may be 80 degrees, but, take that same RV to an area with an ambient temp in the 30's or 40's, and everything changes. The water going through the heater has to go much slower to be warmed the extra 30-40 degrees. Meaning your flow has to become nearly nothing or you live with lukewarm (at best) water.

[mr_andyj]

for RV use:

pros: none

Cons: the water will be cold at first, then if you are turning water off to save water between soaping and washing the water in the heating element will get extra hot from the residual heat that the non-moving water is picking up (is meant for water to run through and pick up some heat). When you turn nozzle back on you get that hotter water. Some complain it is too hot.

These are really meant for running the water continually. I really wanted to go this route but research turned up NOBODY that liked it for an RV. Not unless you have access to unlimited water and can run continuously

.

[kedanie]

From someone who actually has a tankless water heater, don’t give much credibility to those that run them down while never having one.

We have been running ours now for over 5 years and it works very good. Over the long haul we have found that it actually uses less propane than a tank style. Yes, they don’t have a electric option. When in low flow areas, just turn on your pump and all is fine. When dry camping, we use a pan to catch the cold water while waiting for hot and use it for toilet flushing. That cold water is typically less that a half gallon. Don’t forget, tank style heaters have cold water in the lines also.

Don’t run something down when you have never tried one. That is just fear mongering.

Keith

[Gdetrailer]

CavemanCharlie wrote:

wra wrote:

wanderingaimlessly wrote:
Your in florida, for home or rv use you only need to heat the water 30-40 degrees to get the temp you want, from an rv tank you may not need even that much, but as temperature range changes increase, the difficulties regulating it do as well.

I have used changing water pressure less than 20 lbs to 60 lbs (a well pump system) with no problem regulating water temperature.

The main point is to have only the hot water faucet turned on. Having he hot and cold water turned on provides a path for cold water to the shower head, and causes the tankless heater to have less water go through it. That situation causes the tankless heating unit to turn off prematurely, and cold water continue to flow.(burr!) The tankless heater should be set to the desired shower head water temperature. Let it do its job.

So it sounds like in a home that it's a learning curve. Most people don't want to change their habits and don't want to learn new things.

That being said, it also sounds like it might not work as well in a RV where the parameters of flow usage and other things can change.

Unless tankless water heaters have changed considerably over the last few years, they have absolutely no temperature adjustments.

You have two designs, one with full on/full off burner that requires a min of .6 gpm flow or a modulated burner that varies the burner according to the flow.

Both however still have a minimal water flow required to turn on the burner.

Both use a very high BTU burner.

Both can only raise the water temperature to a certain point over the incoming water temp and the amount of temp rise is a factor of how fast the water is flowing. Slow moving water will have a much higher rise in temp, but now you risk the burner not staying on and you get a cold burst of bone chilling water or even worse end up with unanticipated scalding hot water..

In sticks and bricks instant water heaters are often installed with a tempering valve to help smooth out the cold/hot/cold variation with water flow.. Tempering valves are not typically built into water heaters.

Something else never mentioned is the need to periodically having to clean the tubes in a instant water heater. Water contains a certain natural amount of minerals (calcium, lime, iron) suspended in the water. Instant water heaters are prone to clogging from this mineral build up in the tubes. Water sources like unfiltered/unprocessed water wells can clog an instant water heater in a relative short amount of use.

In a RV, there is no advantage for using a instant water heater..

Standard 6 gallon RV water heater can easily supply you with 10-15 minute scalding hot shower. They are typically set to 130F-135F and you only need to mix a small amount of hot water into a lot of cold water to get a really nice steamy shower.

If done correctly, it works a bit like 5:1 ratio, 5 parts cold to one part hot. If you use .5 gpm of hot water, 6 gallon water heater can get you about 12 minutes of scalding hot water and as new cold water mixes it will cool down some towards the 15 minute mark and you simply reduce the cold water some..

I have found that if I turn on just enough hot to get water flowing and then add a bunch of cold just enough to make the shower head spray lightly three of us can get back to back (very little recovery time between) showers without anyone getting a cold shower.

Are you going to have a RV shower pin you against the shower walls like sticks and bricks?

Nope.

But, it will be plenty of water to get the cleaning job done..

Camping is not the same as home, there are compromises and if you want to be pinned to the shower walls then use the campgrounds showers or stay at home.

[CavemanCharlie]

wra wrote:

wanderingaimlessly wrote:
Your in florida, for home or rv use you only need to heat the water 30-40 degrees to get the temp you want, from an rv tank you may not need even that much, but as temperature range changes increase, the difficulties regulating it do as well.

I have used changing water pressure less than 20 lbs to 60 lbs (a well pump system) with no problem regulating water temperature.

The main point is to have only the hot water faucet turned on. Having he hot and cold water turned on provides a path for cold water to the shower head, and causes the tankless heater to have less water go through it. That situation causes the tankless heating unit to turn off prematurely, and cold water continue to flow.(burr!) The tankless heater should be set to the desired shower head water temperature. Let it do its job.

So it sounds like in a home that it's a learning curve. Most people don't want to change their habits and don't want to learn new things.

That being said, it also sounds like it might not work as well in a RV where the parameters of flow usage and other things can change.

[wra]

wanderingaimlessly wrote:
Your in florida, for home or rv use you only need to heat the water 30-40 degrees to get the temp you want, from an rv tank you may not need even that much, but as temperature range changes increase, the difficulties regulating it do as well.

I have used changing water pressure less than 20 lbs to 60 lbs (a well pump system) with no problem regulating water temperature.

The main point is to have only the hot water faucet turned on. Having he hot and cold water turned on provides a path for cold water to the shower head, and causes the tankless heater to have less water go through it. That situation causes the tankless heating unit to turn off prematurely, and cold water continue to flow.(burr!) The tankless heater should be set to the desired shower head water temperature. Let it do its job.

[Desert_Captain]

IMHO:

Given the history, reliability and efficiency of the existing LP/AC water heaters found throughout the RV industry for decades, going to a "Tankless" system is searching for a solution for which there is no known problem. :S

{The government does this a lot... but I digress.}
As always... Opinions and YMMV.

:C