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Main Forums => The Roundtable => Topic started by: MillCreek on January 28, 2021, 03:50:01 PM

Title: Opinions on tankless water heaters
Post by: MillCreek on January 28, 2021, 03:50:01 PM
It has been a while since the last discussion of tankless vs. tank water heaters.  Perhaps the technology is so mature that nothing changes.  We are five years into our Rheem gas water heater and I am pondering when it comes time to replace: tankless vs. a new tank.  It would be propane powered.  I have never owned a tankless water heater and have little idea of the pros and cons.  I ask the Collective to edumacate me.
Title: Re: Opinions on tankless water heaters
Post by: Nick1911 on January 28, 2021, 03:53:36 PM
Only 5 years in?  Come ask in 2030 or so.  =)

I've installed a few for customers.  I don't think I'm ready to put one in my house, it's a lot of complexity - a lot that can go wrong which my old gas water heater doesn't have.

Installing them can be a pain, high efficient gas models require access to everything - hot and cold water lines, drain, 120v power, natural gas, and a new flue + combustion air intake venting.
Title: Re: Opinions on tankless water heaters
Post by: Brad Johnson on January 28, 2021, 04:18:04 PM
Pro: They're great if you need endless hot water or don't have space for a traditional water heater. You don't have the standby losses of keeping water hot when there's no demand.
Cons: Depending on energy type, size, and mfg, they can be horrifically energy inefficient compared to modern water heaters in terms of BTU per degree per gallon. (i.e. - Some are pretty decent. Some suk bawls.) They also must be flushed regularly, usually yearly, to combat scale buildup. Finally, they can ultimately be more expensive to purchase compared to a traditional water heater because and retrofitting for one can get spendy.

In general, if you use hot water several times a day but don't need an endless supply, a traditional water heater is likely a better solution. It's cheaper to buy, simpler to install and maintain, and more financially viable overall.

However, if you have a scenario where hot water is needed only occasionally (maybe every few days), or regularly need amounts in excess of what a traditional water heater can supply, then a tankless unit may be a better solution. Just realize that retrofitting for one varies from expensive to 'Damn!', and annual maintenance is an absolute requirement if you want them to last and/or maintain efficiency.

Austin builder Matt Risinger has a good "what to consider" video on tankless vs. traditional.

https://www.youtube.com/watch?v=8RFuFBI3r2c

*edit to add* Forgot to mention how critical knowing your water supply temp is when sizing a tankless. You absolutely must know your water supply temp if you are to get a properly sized unit. There is a finite input/output temp rise for a given BTU heater. If you don't account for the intended delta, it's way easy to undersize the unit. That endless supply doesn't mean much if it's only lukewarm. My sister and BIL found that out the hard way. Ended up having to install additional circuits for a larger unit, and that was on top of the retrofit costs already incurred.

Brad
Title: Re: Opinions on tankless water heaters
Post by: Boomhauer on January 28, 2021, 04:29:51 PM
I had one in my first house took a long time to get the hot water to the faucet but once it was there it was great. I didnít have to install it or pay for the propane so for me it was a good deal.

Title: Re: Opinions on tankless water heaters
Post by: MillCreek on January 28, 2021, 04:41:47 PM
Brad, noting your comments about scale, we are on a well.  The well water does have some degree of mineral content and we see limescale buildup due to the calcium content.  We have little, if any, iron in the water. Does that change your thoughts?
Title: Re: Opinions on tankless water heaters
Post by: Brad Johnson on January 28, 2021, 04:47:03 PM
Brad, noting your comments about scale, we are on a well.  The well water does have some degree of mineral content and we see limescale buildup due to the calcium content.  We have little, if any, iron in the water. Does that change your thoughts?

If you already experience visible lime and calcium scaling, you may want to up the flush schedule to semi-annually. From what I see and read, tankless units are hella sensitive to scale buildup. The flush process isn't complicated, but at $125-ish a pop the kits aren't cheap and the process is time-consuming. The channel I linked above has a video on the flush procedure.

Brad
Title: Re: Opinions on tankless water heaters
Post by: Jim147 on January 28, 2021, 05:06:28 PM
I've worked on and installed several. Outside of a rarely used weekend cabin or a restaurant I haven't really seen a need for one.
Title: Re: Opinions on tankless water heaters
Post by: RocketMan on January 28, 2021, 07:59:43 PM
We've had a Rinnai tankless water heater for a few years now.  It uses natural gas for the heat source and also requires 120VAC for the control circuits.  We love the darn thing.  It heats water quickly to the set temperature and doesn't have any problem with colder winter feed water temperatures.
Our unit was about $1200 if I remember correctly, and the plumbers charged us $800 to install it, including all exhaust venting.  Of course, we did get the family rate on that since the plumbers were my stepson's inlaws.  It also helped that I had previously replaced all the copper water pipe with Pex pipe and fittings.
The tankless heater replaced a standard 40 gallon electric water heater, so we saw our electric bill go down.  The natural gas bill went up a bit, but the decrease in the electric bill was substantially more.  It's paid for itself by this point.
Title: Re: Opinions on tankless water heaters
Post by: zahc on January 28, 2021, 10:07:21 PM
They work, but aren't worth it. Expensive to install, prone to being installed incorrectly, expensive to fix, require maintenance. Why not just get a tank type that sits there and just works. For what I paid replacing the cracked manifold on my Rinnai, I could have just converted back to tank type almost twice over.

If you cannot spare the space for a tank or otherwise have no choice then sure, they do work. Just double-check the requirements for gas line size, pressure, max run, ambient temperature, water temperature, water hardness, and if mounted outside, don't forget freeze protection and protection for the freeze protection in case of power outages.
Title: Re: Opinions on tankless water heaters
Post by: sumpnz on January 28, 2021, 11:08:02 PM
Whatís the expected life span of a traditional electric water heater given typical lax maintenance and well water (high iron content)?  Is my 16-17 year old heaterís fuse about done?
Title: Re: Opinions on tankless water heaters
Post by: MillCreek on January 29, 2021, 08:38:18 AM
In our previous house, we had a builder-grade electric water heater with a five year warranty.  It lasted for 15 years before springing a leak.
Title: Re: Opinions on tankless water heaters
Post by: K Frame on January 29, 2021, 10:07:50 AM
Whatís the expected life span of a traditional electric water heater given typical lax maintenance and well water (high iron content)?  Is my 16-17 year old heaterís fuse about done?

Well, a lot would depend on the quality of the water heater to begin with. A "9 year" water heater has a better anode and better interior coatings than a "5 year" model.

The easiest way to make a water heater last a LOT longer?

Replace the anode rod regularly.

In your case? You're likely on borrowed time.

A quick way to find out the state of your water heater is to drain a few gallons of water out of the bottom drain and into a bucket. Then leave it settle and look for rust flakes.

If you find rust, start planning on a replacement now. Not later.
Title: Re: Opinions on tankless water heaters
Post by: JTHunter on January 30, 2021, 12:15:33 AM
Don't you have to increase the diameter of the pipes feeding gas (natural or propane) to a tankless due to the higher fuel requirements?
Title: Re: Opinions on tankless water heaters
Post by: Jim147 on January 30, 2021, 07:53:50 AM
Depends on what is there but yes they need to be sized to the water heaters demand.
Title: Re: Opinions on tankless water heaters
Post by: RocketMan on January 30, 2021, 09:55:01 AM
Depends on what is there but yes they need to be sized to the water heaters demand.

We've got a half inch copper tap off the main NG line feeding our Rinnai tankless.  It's the smallest gas line in the house.
Title: Re: Opinions on tankless water heaters
Post by: Jim147 on January 30, 2021, 10:07:14 AM
Yeah it's a bunch of math to figure out. Start at the meter and end at the last leg. And up all appliances on each run and go from there.
Title: Re: Opinions on tankless water heaters
Post by: MillCreek on May 02, 2021, 10:42:12 AM
14 months after the Rheem gas heater needed a new flammable vapor sensor, for $ 265, the exact problem occurred again.  I did the software reset and it did not work.  Just like the first time, and again indicating a hardware problem with the vapor sensor. 

So I called the plumber and learned some interesting things:

Our Rheem unit is six years old, the same age as the house, and it has a six year warranty.

The plumber agrees that it does not make sense to put more money into a tank that is likely at the end of its service life.

He is not a fan of the Rheem products, and it would cost about $ 3200 to replace the existing unit with another Rheem or another gas equivalent

He too is on propane tanks and well water, and a couple of years ago replaced his tank with a Noritz EZ111 tankless water heater as a test.  The EZ111 has the water connections on the top, as does a tank, making the install much easier.  He is a real fan of the Noritz unit in terms of durability as long as you drain and descale it once a year.  He says the Noritz has a higher upfront cost by several hundred dollars, but you will see a payback in the lesser amount of propane used, since the tankless is not constantly cycling a propane burn on and off to keep 50 gallons of water at temperature.

So I signed us up for the Noritz install.  It should be in stock at the Seattle plumbing supply house, so we should have a new water heater by the middle of this week.
Title: Re: Opinions on tankless water heaters
Post by: MillCreek on May 02, 2021, 06:51:58 PM
Out of curiosity, I looked up the same model of Rheem water heater that we have.  Home Depot sells the same 50 gallon power vent tank for just under $ 1200 out the door.  In reading further about power vent gas water heaters, they cost 50 to 75% more than a direct vent model, is more expensive to install, and six years warranty is considered top of the line.  Also of interest are the many negative comments about the flammable vapor sensor, including some cases in which a newly-installed unit has this error code immedately on start up.  When this problem first happened 15 months ago, i remember thinking how odd it was that the majority of the plumbers I called said they do not work on Rheem units.

This is the first gas water heater I have ever had.  I now realize how easy it was to maintain and replace the electric units I had before.  If I had an electric water heater breaker in the panel and circuit in the garage in the right location, I would just go with an electric heater.
Title: Re: Opinions on tankless water heaters
Post by: Jim147 on May 02, 2021, 07:27:52 PM
Looks like I need to up my install charges again.
Title: Re: Opinions on tankless water heaters
Post by: cordex on May 02, 2021, 09:05:30 PM
This is the first gas water heater I have ever had.  I now realize how easy it was to maintain and replace the electric units I had before.  If I had an electric water heater breaker in the panel and circuit in the garage in the right location, I would just go with an electric heater.
I have had a gas water heater in my current house for 14 years.  It is (as far as I can tell) the original cheap contractor model installed when the house was built 17 years ago.

So far I have had to replace the pilot light sensor once.

In my new house I'm going to have an electric hot water heater ... I was just thinking how that was going to add to my maintenance load.
Title: Re: Opinions on tankless water heaters
Post by: K Frame on May 04, 2021, 08:17:00 AM
"In my new house I'm going to have an electric hot water heater ... I was just thinking how that was going to add to my maintenance load."

Are you also going to have an electric cold water cooler?

And, having had electric water heaters all of my life, I'm trying to figure out how one will add to your maintenance load.

Pretty much everything you have to do for a gas water heater you have to do for an electric water heater.
Title: Re: Opinions on tankless water heaters
Post by: Brad Johnson on May 04, 2021, 11:07:40 AM
I still prefer gas water heaters, mostly for the ability to continue supplying hot water during a power failure (callback to our local energy provider's new ERCOT affiliation). Doesn't hurt that natural gas is dirt cheap around here.

Brad
Title: Re: Opinions on tankless water heaters
Post by: K Frame on May 04, 2021, 11:13:47 AM
I'd love to have a gas water heater.

They're cheaper to operate, SOME of them will work even with a power outage (models that require 120 volt for venting are becoming increasingly common), and they recover a lot faster.
Title: Re: Opinions on tankless water heaters
Post by: charby on May 04, 2021, 11:43:59 AM
I wanted a gas tankless for years, the more I read about them, I don't want them for my house. I look at the cost and the life, I'm having a hard time penciling the fuel savings vs replacing my current setup.

Currently I have a 17 year old 40 gallon tank water heater. I'm probably just going to upgrade it to a 50 gallon water heater sometime in the next six months. I see that the local big box lumber yard/hardware store has a 12 year 50 gallon non power vented water heater for ~$650. They ain't nothing to install for me.
Title: Re: Opinions on tankless water heaters
Post by: cordex on May 04, 2021, 11:50:35 AM
And, having had electric water heaters all of my life, I'm trying to figure out how one will add to your maintenance load.

Pretty much everything you have to do for a gas water heater you have to do for an electric water heater.
I've helped replace a number of comparably new failed electric units for friends and family but my gas unit has been very reliable and low maintenance with the exception of the $6 thermocouple I replaced.  I could be entirely wrong - just going on what I've seen.
Title: Re: Opinions on tankless water heaters
Post by: MillCreek on May 04, 2021, 11:52:01 AM
We discovered to our chagrin that the fancy Rheem power vent gas tank does not operate during a power outage.  Which is actually fine, since the well doesn't work during a power outage either.

I was talking to the neighbor down the street who had the exact same Rheem tank unit replaced by the exact tankless model we are getting, installed by the same plumber.  So far, he really likes the tankless, likes the extra space in his garage, and has seen a drop in his propane usage due to the tankless firing only on demand.  We are going to split the cost of getting one of the scaling/cleaning kits for the annual maintenance of the tankless.
Title: Re: Opinions on tankless water heaters
Post by: Ben on May 04, 2021, 12:00:50 PM
The house here came with an 80 gal AO Smith Promax electric. Shows it was installed when the house was built in 06. When the HVAC guys inspected it when they installed my new HVAC when I moved in, they said it still looks to be running strong.

Electricity here isn't as much a cost issue as it is in some other states, so electrics seem to be popular. While I know they have them, I don't believe I ever lived in a place or saw a place in CA with an electric. Gas everywhere, even rural areas where they were propane.  Of course that's standard and not tankless. The last rental house I had there was built new in 08 IIRC, and that one came with a tankless, which it seemed builders were moving to at the time.

As for maintenance and breakdowns, I'm wondering if it's less to do with gas vs electric and more to do with age, older being better. I had a great plumber for my rentals in CA, and the couple of times something needed to be fixed on a water heater at my triplex, which was built in 87, I would say, "Let's buy a new one" and he would say, "let's not". He loathed the newer water heaters. He may have had a point. on one of the units, the water heater never had a problem the entire time I owned the property, which was from ~1989-2015.

I know that one of my plumber's big issues, for CA at least, was that the newer water heaters had some kind of required energy efficiency / pollution control crap on them that always failed.
Title: Re: Opinions on tankless water heaters
Post by: Brad Johnson on May 04, 2021, 12:09:54 PM
Electricity here isn't as much a cost issue as it is in some other states, so electrics seem to be popular.

A lot of the new mid-range developments around here are all electric simply because the developer didn't want the cost of running gas lines, plus the city having pretty strict limits on propane tanks. Only way to have an installed propane tank in the city limits is if your in an area that's been annexed and grandfathered. Even then it's a giant pain.


We discovered to our chagrin that the fancy Rheem power vent gas tank does not operate during a power outage.  Which is actually fine, since the well doesn't work during a power outage either.

Yeah, that's definitely something to consider. Fortunately we're on city water so pressure stays relatively constant even if the power fails. Not sure what the city water towers' designed-in reserve periods are, but it's more than enough to handle a couple of hours, maybe a couple of days. We also get about half the city's water from a gravity-fed source. Even if the entire grid goes down, some water will at least be flowing and all the main city pumps and tower lift pumps have been upgraded with emergency power sources.

Brad
Title: Re: Opinions on tankless water heaters
Post by: MillCreek on May 04, 2021, 12:19:58 PM
My wife points out to me that an appreciable number of the new houses being built in this area have tankless heaters installed.  These are for houses listing at $ 700K upward, which is most of the new houses being built.  All the new construction has water heated by gas.  We have not seen an electric water heater in new construction for a considerable time.
Title: Re: Opinions on tankless water heaters
Post by: K Frame on May 04, 2021, 12:46:38 PM
Ideally, both electric and gas units are pretty maintenance free.

The more complex they become, however, the more maintenance/repair becomes an issue.

The biggest reason why electric units fail more rapidly than gas units is they have electrical current running through them that tends to attack the tank and causes it to fail more quickly. That's why the best thing you can do to keep your electric water heater running leak free for a long time is to replace the sacrificial anode when it's depleted.

That is becoming more of an issue with gas units, as well, as more and more they have connections to electric power for venting, running the gas valves, etc.

Poly tank electric water heaters are slowly making inroads into the industry, but I THINK right now Rheem is the only widely available manufacturer.

Title: Re: Opinions on tankless water heaters
Post by: MillCreek on May 04, 2021, 01:05:45 PM
^^^It is interesting you mention the anode.  I was used to periodic replacement of the anode in my electric heaters.  I asked the plumbers about this on the gas Rheem unit 15 months ago when the first vapor sensor went out.  They said in this area, not to bother with replacing the anode.  I wonder if this was because the unit was gas fired, or that the water supply was from a well.
Title: Re: Opinions on tankless water heaters
Post by: K Frame on May 04, 2021, 01:09:09 PM
Third possibility...

Your plumber is hoping for more work in the future... :)

I don't know the answer to that.