Tankless water heaters

Sac Arrow

Sac Arrow

Touchdown! Greaser!
PoA Supporter
Joined
May 11, 2010
Messages
20,749
Location
Charlotte, NC
Display Name
Display name:
Snorting his way across the USA
IMG_6013.jpeg
Zero research. Did them on a project once but didn’t do that facet of the design. Had to replace the home water heater. The Other Person brokered the deal and this is how it came out
 
So how do you like it? Our town's water is hard and it eats the tanks. Tanks no longer have that glass lining they used to have to prevent corrosion of the steel tank walls. They're just finished with some sort of hi-temp paint or something.
 
I love my Rinnai tankless. Installed it about 3 years to replace an 80-gallon electric. I out the LP tankless in the garage and gained a whole new closet in the house.

Love the unending hot water and no energy use when we aren’t home. As a bonus, my generator can easily provide the electricity needed for the tankless.

I spend about an hour once a year descaling. Easy peasey.

I would never go back.
 
My current home was purchased with 3 tankless units servicing 4 full/2 half baths and indoor/outdoor kitchen sinks/laundry room (natural gas Rheem units). I was VERY skeptical as I heard it takes a while for hot water to reach the tap and figured I would end up putting in tanks eventually. Turns out, I love them. It doesn’t take much, if any longer, time for hot water to flow and we have endless hot water. If I had to build a new home, I would definitely put them in. I did have to replace one unit due to failure on the emergency heater for the heat exchanger failing and, during a period of sub freezing temperatures for many days the exchanger froze and split (the unit was installed as an exterior unit).
 
I have several tankless at my cabins which are off grid. They work great. One of them needed a booster water pump from an RV which cost $56 extra but I have gobs of hot water instantly. The electric element type use a ton of amps. Usually two or three 60amp breakers for one tankless. I don't have a lot of use through them, but they've been working flawlessly each time I go there.
 
I put a Bosch unit in our cabin about 15 years ago and it's still going strong... no electricity needed and no pilot, it has a little turbo generator that generates electricity for the controls and ignition from the water flow. Then installed a larger Rheem unit in the house a couple of years ago, that one needs electric but so does the well pump anyway. Both are LP. I'll never go back to tanks.
 
The only complaint I have with the one I use is that the kitchen sink faucet can’t be throttled down to eliminate spray while rinsing dishes and still provide not cold water.
 
I installed one in our RV. Tankless makes sense in RV's because tanked water heaters are typically 10 gal or less. In the RV it saves weight and provides endless hot water. The caveat is I have had to repair the thing multiple times. It has experienced board failure, sensor failures, fan failure, etc.

When the fan fails is particularly interesting. The fan brings in fresh air to the combustion area and exhausts combustion gases. When the fan fails it starves for oxygen and the flame goes out; the water in your shower goes cold. You turn the water off, then back on. The water heater attempts restart but doesn't have oxygen to reignite. Each time a restart attempt occurs some propane is released into the combustion area. Cold in the shower you turn the water on again hoping for hot water. At this point you hear a boom as there is now enough oxygen for it to ignite again; a fireball is shot out of the side of your RV water heater.

In spite of the aforementioned issues, I advocate for tankless water heaters in RV's as the benefits outweigh the drawbacks. When we had apartments I looked into tankless water heaters as a possible replacement for the large commercial tanked water heaters we had. If you get 200k BTU or more an annual boiler inspection may be required. Proper sizing is key with these units. Before buying you want to consider your incoming water temp, desired water temp, figure the rise required and GPM required. As mentioned previously, the electric only models require alot of power; you will likely need ng or propane.
 
I've had one in a rental that been working great for 10 years. Only have to change a single D cell for the ignitor every year. We have extremely acid water, and the copper exchanger is holding up fine, but the flow control valve is starting to get stiff. It's an Excel brand, bought it off Ebay so finding parts may be problematic. They still have a distributor in FL, but customer service is unresponsive.
 
Put a tankless in back in 2016 when I built my house. Also put in a steam shower with a bench. Highly recommend.
 
Somehow, living in a geologically active area having 50 gallons of potable water in my basement gives me a warm fuzzy. Would definitely put one in a rental.
 
Bought a vacation home w/ one that didn't work; replaced it a new one that failed soon. Gave up and put in a 25 gal tank. Not likely to try again.
 
Tankless concern me about legionella (I’ve seen too many of them installed at point of use instead of a proper hot water system with tempering valves in commercial settings). But I would like to have a mini “boiling water” tanked system under my kitchen sink. When I was a kid my grandparents had a boiling water tap in the kitchen (one of my uncles had built it as a science fair project in the 1960’s). It was usefull as all get out, boiling potatoes? Instantly boiling hot water in the pan, put it on the stove and it boiling, making coffee? Put the grounds in and fill the dripper, want a boiled egg, just put it in a pan and fill it, when it was cool enough to take out it was done, that thing was awsome but could never be marketed because of liability issues.
 
Flatiowa said:
Tankless concern me about legionella (I’ve seen too many of them installed at point of use instead of a proper hot water system with tempering valves in commercial settings). But I would like to have a mini “boiling water” tanked system under my kitchen sink. When I was a kid my grandparents had a boiling water tap in the kitchen (one of my uncles had built it as a science fair project in the 1960’s). It was usefull as all get out, boiling potatoes? Instantly boiling hot water in the pan, put it on the stove and it boiling, making coffee? Put the grounds in and fill the dripper, want a boiled egg, just put it in a pan and fill it, when it was cool enough to take out it was done, that thing was awsome but could never be marketed because of liability issues.
Click to expand...

The bride bought an 'instant hot' kettle which I believe is an invection process. However it works, it works great. Heats a quart of water to boiling in about 90 seconds. Almost as good as an insta-hot tap without the plumbing and electric install.
 
Chip Sylverne said:
The bride bought an 'instant hot' kettle which I believe is an invection process. However it works, it works great. Heats a quart of water to boiling in about 90 seconds. Almost as good as an insta-hot tap without the plumbing and electric install.
Click to expand...
I don't know which kettle you have, but the term is "induction". And, yes, they can be very fast!
 
well darn it. I'm due for a new water heater and you made me want one of these again *laugh*
 
I guess in theory you are saving on gas because you aren't constantly heating the unit, but for 6+ AMU's I doubt I'll ever get a return. The water heater's usage is only about five or six dollars a month. It must be pretty efficient though - the vent gasses are so cool that they use a plastic vent with a condensate drain.
 
172andyou said:
I don't know which kettle you have, but the term is "induction". And, yes, they can be very fast!
Click to expand...

Invection, induction, both cause heat, right?
Too much election, not enough flying.
 
Have tankless in my condo,not a big fan.
 
Kevin Holbrook said:
I love my Rinnai tankless. Installed it about 3 years to replace an 80-gallon electric. I out the LP tankless in the garage and gained a whole new closet in the house.

Love the unending hot water and no energy use when we aren’t home. As a bonus, my generator can easily provide the electricity needed for the tankless.

I spend about an hour once a year descaling. Easy peasey.

I would never go back.
Click to expand...
Ours is running about 11 years strong. Descale once a year is super easy. I see no reason to go back.
 
We've got two Rinnais. One was installed in 2009 and the other in 2016. No problem with either one.
 
172andyou said:
Wait, what? Most people who have even heard of legionnaires disease go with tankless to lower risk.

e.g. https://www.healthcarefacilitiestod...acteria-Proliferation-in-Water-Heaters--28836
Click to expand...
Notice commercial point of use in lue of proper hot water system with mixing valve in my post, think bathroom touch less sinks (the ones without handles, just a sensor to turn on warm water when your hands are under it. Proper way is a hot water line hot enough to deal with it then temper it with cold water through a mixing valve. On demand set to “warm” with one line feeding it is a lot cheaper but a perfect breading ground if there are any issues with the chlorination or anything in the system that uses up the free chlorine before it reaches it.
 
I had one in the shop for radiant floor heating. Worked great!

Now I have two for domestic hot water in the house. The ONLY thing I don't like about it is that they have a minimum flow. So if you want a low flow of hot water, you won't get any at all (checked with Navien and they confirmed). That's a problem for me in Florida during the summer months. After working outside I want a barely lukewarm shower to cool off. Except all I get is cold water. So I have to turn on the hot water in sink faucet to generate enough demand while I take a shower.
 
I have contemplated putting a small tankless under the kitchen sink. As it is today, the kitchen sink + dishwasher are the farthest point from the tank water heater in the attic (yeah, I know.. it was there when we bought the house and I haven't found a suitable way to move it down to ground level without replumbing the whole dang house), so any time you just need some hot water to wash your hands or rinse something out, it takes a while to get hot water down. It would be nice to have hot water on-demand at that spot. Anybody done this? It might also help me justify running gas to the kitchen so I can get rid of that GDMFPOS (see other 'frugal mechanic' thread for translation) electric range.
 
CJones said:
I have contemplated putting a small tankless under the kitchen sink. As it is today, the kitchen sink + dishwasher are the farthest point from the tank water heater in the attic (yeah, I know.. it was there when we bought the house and I haven't found a suitable way to move it down to ground level without replumbing the whole dang house), so any time you just need some hot water to wash your hands or rinse something out, it takes a while to get hot water down. It would be nice to have hot water on-demand at that spot. Anybody done this? It might also help me justify running gas to the kitchen so I can get rid of that GDMFPOS (see other 'frugal mechanic' thread for translation) electric range.
Click to expand...
Ooh, I am interested in this too. Same issue, and my current water heater is pretty long in the tooth
 
donjohnston said:
I had one in the shop for radiant floor heating. Worked great!

Now I have two for domestic hot water in the house. The ONLY thing I don't like about it is that they have a minimum flow. So if you want a low flow of hot water, you won't get any at all (checked with Navien and they confirmed). That's a problem for me in Florida during the summer months. After working outside I want a barely lukewarm shower to cool off. Except all I get is cold water. So I have to turn on the hot water in sink faucet to generate enough demand while I take a shower.
Click to expand...
That's odd, most showers use more water than a sink faucet. I very rarely shower at home, so I haven't been able to test it out yet. It is a Navien unit.
 
Flatiowa said:
...But I would like to have a mini “boiling water” tanked system under my kitchen sink. When I was a kid my grandparents had a boiling water tap in the kitchen (one of my uncles had built it as a science fair project in the 1960’s). It was usefull as all get out, boiling potatoes? Instantly boiling hot water in the pan, put it on the stove and it boiling, making coffee? Put the grounds in and fill the dripper, want a boiled egg, just put it in a pan and fill it, when it was cool enough to take out it was done, that thing was awsome but could never be marketed because of liability issues.
Click to expand...
Bought one of these a month ago. The only part of the unit that gets hot is the glass. The base of the pot and the stand remain cool. The heating system is completely encased and insulated in the pot's base. It's FAST!

 
Flatiowa said:
Notice commercial point of use in lue of proper hot water system with mixing valve in my post, think bathroom touch less sinks (the ones without handles, just a sensor to turn on warm water when your hands are under it. Proper way is a hot water line hot enough to deal with it then temper it with cold water through a mixing valve. On demand set to “warm” with one line feeding it is a lot cheaper but a perfect breading ground if there are any issues with the chlorination or anything in the system that uses up the free chlorine before it reaches it.
Click to expand...
Got it. So not a problem with tankless, but with installation. If you mix your warm water near the tank heater the same problem would be there, right? And if I ran hot water from the tankless to the sink then I'd be fine?
 
do any of you have electric versions?

We just recently bought an office building for my wife. I little old bungalow house that had been at some point converted to an office. It has a small tank heater in the crawl space... an open wet dirt crawl space
looks like a homeowner's special installation and is old...but still works
So I've had in mind that after the dust settles from the higher priority remodeling, I'll be considering a small tankless. Don't need much, just a kitchen and bathroom sink for hand washing, etc... no bathing, no laundry. the place used to have natural gas. It's still under the road but the service drop has been abandoned, so gas isn't practical
 
Sac Arrow said:
That's odd, most showers use more water than a sink faucet. I very rarely shower at home, so I haven't been able to test it out yet. It is a Navien unit.
Click to expand...
In the summer, to cool off, I take a shower with almost no hot water. Just enough to take the chill off. IIRC, our Navion requires 1GPM. So to get the demand over that, we turn on the sink faucet. Had I known, I would have added a faucet to the shower. :dunno:
 
Brad W said:
Don't need much, just a kitchen and bathroom sink for hand washing, etc
Click to expand...
They make mini electric tanked heaters for exactly this. A tank would require a lot less demand on your electrical system. On demand electrics can really draw a lot of amps.
 
Brad W said:
Don't need much, just a kitchen and bathroom sink for hand washing, etc... no bathing, no laundry. the place used to have natural gas. It's still under the road but the service drop has been abandoned, so gas isn't practical
Click to expand...
LP is an option if NG service isn't feasible.
 
Brad W said:
do any of you have electric versions?

We just recently bought an office building for my wife. I little old bungalow house that had been at some point converted to an office. It has a small tank heater in the crawl space... an open wet dirt crawl space
looks like a homeowner's special installation and is old...but still works
So I've had in mind that after the dust settles from the higher priority remodeling, I'll be considering a small tankless. Don't need much, just a kitchen and bathroom sink for hand washing, etc... no bathing, no laundry. the place used to have natural gas. It's still under the road but the service drop has been abandoned, so gas isn't practical
Click to expand...

I had a small electric flow-through installed in the barn for washing horses. Never really got much more than lukewarm, and as said above even at 220v used a lot of amps. Might work better with less volume throughput, like for handwriting and such. Replaced it with a 20gal conventional electric tank, as Idicn't want lpgas in the barn.
 
In much of SE Asia, hot water is supplied by small electric point of use tankless heaters, e.g. one in the shower and one in the kitchen sink. They seem to work pretty well. Washing machines tend to be small and have their own water heaters.
 
Dan Thomas said:
So how do you like it? Our town's water is hard and it eats the tanks. Tanks no longer have that glass lining they used to have to prevent corrosion of the steel tank walls. They're just finished with some sort of hi-temp paint or something.
Click to expand...
no kidding. I think the water heater in my folks house is approaching 70 years hold and still going strong.

Brian
 
Last edited:
Dan Thomas said:
So how do you like it? Our town's water is hard and it eats the tanks. Tanks no longer have that glass lining they used to have to prevent corrosion of the steel tank walls. They're just finished with some sort of hi-temp paint or something.
Click to expand...
Nowadays the technology is refined to the point that the engineers can calculate exactly how thick to make the coating so they last for the duration of the warranty and no longer. :(
 
You must log in or register to reply here.
Back
Top