Tankless water heaters

[brcase]

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.

This is what I did (Bosch 2.5 gallon, under the kitchen sink) I got tired of running the water for a full minute to get hot water. I have it plumbed to the hot water line from the main water heater, so by the time I use the 2.5 gallons I am getting hot water from the main heater. But I very rarely use that much water at one time, so it doesn't work very hard as it pretty much just keeps the already hot water available at the sink, and rewarms the water that has cooled between the main water heater and kitchen.

Brian

 

[DCR]

We have a tankless in our apartment. My only gripe is the way the temperature is controlled. On our unit (Navien) the heater come on when it senses water flowing.

If you are running hot water on a very low flow rate heater won't get triggered. This leads to your hot water turning into ice cold water until you open the faucet a bit more. Then you have to flush all the cold water out of the pipes to get it hot again.

Small gripe but it bugs me when I'm trying to do dishes and suddenly water turns ice cold. This is my only experience with tankless heaters so maybe it's a quirk / defect of our unit (a plumber I talked to said it's normal and gave me the flow rate explanation, so I assume I'm not the only one).

 

[FORANE]

We have a tankless in our apartment. My only gripe is the way the temperature is controlled. On our unit (Navien) the heater come on when it senses water flowing.

If you are running hot water on a very low flow rate heater won't get triggered. This leads to your hot water turning into ice cold water until you open the faucet a bit more. Then you have to flush all the cold water out of the pipes to get it hot again.

Small gripe but it bugs me when I'm trying to do dishes and suddenly water turns ice cold. This is my only experience with tankless heaters so maybe it's a quirk / defect of our unit (a plumber I talked to said it's normal and gave me the flow rate explanation, so I assume I'm not the only one).

Normal

Tankless have their place, but if you want reliable hot water the old fashioned tanked water heaters are best.

 

[Domenick]

We have a tankless in our apartment. My only gripe is the way the temperature is controlled. On our unit (Navien) the heater come on when it senses water flowing.

If you are running hot water on a very low flow rate heater won't get triggered. This leads to your hot water turning into ice cold water until you open the faucet a bit more. Then you have to flush all the cold water out of the pipes to get it hot again....

Tankless water heaters need a minimum flow to keep them cool and prevent them from burning up, hence your issue.

 

[Sac Arrow]

Normal

Tankless have their place, but if you want reliable hot water the old fashioned tanked water heaters are best.

See, that's the whole thing. The verdict isn't out on the reliability of the tankless and hopefully won't be out for a long time, but the tanked water heaters haven't been reliable. The tankless replaces the third, maybe even the fourth unit whose failure mode has been to split open and create a huge flood. At least this time the tank didn't leak, but the ignitor unit gave out. I probably could have just replaced that component but I viewed it as a ticking time bomb for several reasons. And when it was removed, it couldn't even be drained normally because the manufacturer thought it would be a stellar idea to put plastic threads in the drain valve and of course they stripped on the first attempt to do a maintenance flush of the tank. The hose bib had to be wrenched out but the resulting mess was still less than was normal for the course.

 

[NoBShere]

We have had a tankless in the house for about 15 years and cabin for about 5. We switched to tankless to lower energy costs and reduce space consumed by water heater. Our house has hard water so I was advised to flush with a 50/50 vinegar and water solution annually, which i have done. I never noticed a difference when we switched to tankless. I really didn't expect it to last 15 years but, here we are. I'm familiar with heat exchangers in industry but, I just assumed the residential versions would be less robust. I have friends that have had their tankless on the outside of their house for close to 20 years (they feed me with beers once a year to flush it for them) without any issue. Neither of our households have time for kids so just two adults per home which lowers the usage. btw, these are gas fired, i have no experience with electric.

 

[Kiddo's Driver]

Rinnai natural gas tankless since 2016. Love it.
I should be better about doing the vinegar flush every year. I've managed to do it every 4 years.
I might be better at it going forward because I found out that if you pour vinegar on your wood fence the carpenter bees leave the wood alone. That incentivizes me to do my flush, then use that used vinegar to treat my fence instead of pouring new vinegar on the fence. I'm frugal. Two uses out of one product? You got it.

 

[Baked Potato]

If you pour vinegar on your wood fence the carpenter bees leave the wood alone

Oh, weird - that's something I'll remember next spring.

But are you ok with your property line smelling like a Boardwalk Fries?

 

[Kiddo's Driver]

Oh, weird - that's something I'll remember next spring.

But are you ok with your property line smelling like a Boardwalk Fries?

The strong smell goes away within a day. The mild smell is gone within a week. The protection lasts for about 2-3 months.
It was one of those "I read it on the internet" things. I doubted it, but tried it. It was absolutely effective for me. We went from seeing 20+ carpenter bees a day to not seeing any for a couple months.

 

[FORANE]

See, that's the whole thing. The verdict isn't out on the reliability of the tankless and hopefully won't be out for a long time, but the tanked water heaters haven't been reliable. The tankless replaces the third, maybe even the fourth unit whose failure mode has been to split open and create a huge flood. At least this time the tank didn't leak, but the ignitor unit gave out. I probably could have just replaced that component but I viewed it as a ticking time bomb for several reasons. And when it was removed, it couldn't even be drained normally because the manufacturer thought it would be a stellar idea to put plastic threads in the drain valve and of course they stripped on the first attempt to do a maintenance flush of the tank. The hose bib had to be wrenched out but the resulting mess was still less than was normal for the course.

Yeah, many or possibly most manufactures have gone cheap. Plastic drain valves are a good example of this. During installation those valves should be changed out. Also there are many manufacturers out there making both tanked and tankless units so quality will vary. My experience with the tankless mirrors all the issues others have mentioned plus many fail to heat instances due to failed sensors or components. The tankless units are more complicated than a simple tanked unit; there's more to break...

Tankless offers significant benefit in an RV over a tanked unit. I will install one in any RV I own, and even remove a perfectly functioning tanked unit to install tankless in the setting. Outside of that setting though I would prefer it to just work. Not sure why you have had so many issues with your tanked units. Perhaps you have water that attacks the tanks?

 

[Sac Arrow]

Yeah, many or possibly most manufactures have gone cheap. Plastic drain valves are a good example of this. During installation those valves should be changed out. Also there are many manufacturers out there making both tanked and tankless units so quality will vary. My experience with the tankless mirrors all the issues others have mentioned plus many fail to heat instances due to failed sensors or components. The tankless units are more complicated than a simple tanked unit; there's more to break...

Tankless offers significant benefit in an RV over a tanked unit. I will install one in any RV I own, and even remove a perfectly functioning tanked unit to install tankless in the setting. Outside of that setting though I would prefer it to just work. Not sure why you have had so many issues with your tanked units. Perhaps you have water that attacks the tanks?

The water is hard, but not particularly corrosive. Obviously the water seems to be attacking the tanks. I suppose there could also be some sort of galvanic action issue too through the piping. I assume the pressure tanks are made of steel, which is anodic to the copper piping attached to the fittings.

 

[mandm]

Nice work, I have the same brand. Pretty solid product. You’ll have to clean out the filter every couple years, you might get some error messages one day that say to clean it. Other than that I’m happy with it.

 

[Sac Arrow]

Nice work, I have the same brand. Pretty solid product. You’ll have to clean out the filter every couple years, you might get some error messages one day that say to clean it. Other than that I’m happy with it.

Is that a big deal?

I've been researching the yearly "flush" which I understand is a disconnect and recirc with anti-scalant. I studied the piping array and realized that the installer had put in three-way flush valves, which should make the process easy with the right rig. I might just order the flush kit and go at it myself.

 

[Beachy]

A year ago our 15 year old gas water heater died. We priced out both tankless and gas fired replacements. The tankless was almost exactly twice the cost of a commercial grade gas (with 15 year warranty). Working the math, we'd need 15+ years to amortize the cost difference of the tankless. At 77 years of age, I chose to stick with the "old" style (and save the money up front).

 

[Dana]

We went tankless in the house in part because we liked the one in our cabin, and also because the space made available by getting rid of the tank gave us better options during the kitchen/laundry room remodel.

 

[Barrett50]

I bought this brand when I knew they were made in US: https://www.eztankless.com/household-tankless-water-heaters
Viewing their website now, it appears the units are now built offshore. When I installed mine, since it wasn't electric with a ground lug, I did install a ground strap from the copper heating element to a copper pipe nearby keeping stray electric currents in check. I do drain my unit after every trip, and the drain knob, and threads are all brass. The piping and valves are all brass, and the heat exchanger is aluminum or brass depending on model.

I think all tankless require an annual rinse with white vinegar. It takes a few min to disconnect and use a rubber hose and funnel to rinse with white vinegar.

 

[Sac Arrow]

Dilemma....

I should have caught this while the pipes were being plumbed in, but one of the flush bypass taps (two way valve) was installed directly facing the gas hose, which will probably require the hose to be removed to access the bypass tap.

The valve itself appears to have a true union connection with the tank. Below it, is a copper crimp joint (all the joints are crimp joints.) Should I be able to rotate it 45 degrees with a pipe wrench without destroying the seal?

 

[Dana]

A copper crimp ring joint on Pex? You should be able to rotate it; at least it's worked every time I've done it.

 

[MBDiagMan]

In the back of the house we removed two 70 gallon water heaters and replaced with a large tankless last year. It’s been wonderful and not hard to imagine the energy saving.

 

[Sac Arrow]

A copper crimp ring joint on Pex? You should be able to rotate it; at least it's worked every time I've done it.

It's on a metal valve, not PEX. But, no matter, I believe I have found a solution to my dilemma...

At least I'm pretty sure the fittings to the three way valve are garden hose thread. I'm not going to have to worry about it for a year.

 

[Shawn]

Been in a new build for 6 months now with a tankless and LOVE IT...would have switched before if I knew they were this good.

...but you gotta have one that is specced properly for what you want flow wise as well as what size gas line you have or you will have many of the issues noted above...it is not just a swap of any tankless, you gotta know what you are installing and why to get the right performance for your use down to where and how the unit will be mounted.

Admittedly what energy savings I may have from not heating water 24/7 is lost in the longer showers!

One negative is that most require 120v power to fire the gas heat vs old school tanks that are pure mechanical. I am in the mountains and lose power all the time so my Starlink and water heater are on battery backup so I always have hot water even if generator is not yet fired up.

 

[Dana]

One negative is that most require 120v power to fire the gas heat vs old school tanks that are pure mechanical. I am in the mountains and lose power all the time so my Starlink and water heater are on battery backup so I always have hot water even if generator is not yet fired up.

The fancier ones require power but the simpler ones often don't. As I mentioned earlier the one in our cabin has a turbogenerator to generate electricity from the water flow but many others have pilot lights or are powered by a D cell battery.

The one in our house requires 120V because if the power is out the well pump isn't running anyway.

 

[judypilot]

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.

Tell me more. We have a tank water heater at our cabin and the water there is really hard. Our previous tank (which was in the cabin when we bought it, so I don't know how old it was) was so scaled up it eventually wouldn't drain, which has to be done before winter and, sure enough, the next spring it was blown. If these really can be descaled, it would be worth looking into.

Our current water heater is electric, but we do have gas for the house heater. How hard would it be to put in another line to fuel the tankless heater (or could it be electric, too)?

 

[Sac Arrow]

Tell me more. We have a tank water heater at our cabin and the water there is really hard. Our previous tank (which was in the cabin when we bought it, so I don't know how old it was) was so scaled up it eventually wouldn't drain, which has to be done before winter and, sure enough, the next spring it was blown. If these really can be descaled, it would be worth looking into.

Our current water heater is electric, but we do have gas for the house heater. How hard would it be to put in another line to fuel the tankless heater (or could it be electric, too)?

Several years ago for a project we needed a large volume of hot water at a treatment plant to provide ongoing cleaning for a vibratory RO filter. We ended up putting five tankless heaters in, fired by propane. The electrical demands would have been prohibitive for electric units.

When mine was put in, there were already two taps for gas in to the garage, a large on and a small one. The installer switched the furnace supply to the smaller tap and used the larger one for the tankless. They don't use a lot of gas, but they use a lot of gas at one time. I wouldn't imagine splitting the gas line to be a big deal. It's probably less of a big deal than panel work for an electrical unit.

 

[judypilot]

Several years ago for a project we needed a large volume of hot water at a treatment plant to provide ongoing cleaning for a vibratory RO filter. We ended up putting five tankless heaters in, fired by propane. The electrical demands would have been prohibitive for electric units.

When mine was put in, there were already two taps for gas in to the garage, a large on and a small one. The installer switched the furnace supply to the smaller tap and used the larger one for the tankless. They don't use a lot of gas, but they use a lot of gas at one time. I wouldn't imagine splitting the gas line to be a big deal. It's probably less of a big deal than panel work for an electrical unit.

Thanks, but I'm also interested in the descaling process. How does that work? You must be able to get inside the water heater to descale it.

 

[Sac Arrow]

Thanks, but I'm also interested in the descaling process. How does that work? You must be able to get inside the water heater to descale it.

Take a look at the picture in my first post. The two copper pipes under the unit are the inlet and outlet. The isolation valves on them are two way, and there are garden hose fittings on the valves so that you can connect a couple hoses, one going to a small pump inside a bucket filled with descalant, and another being the return line. You let it recirculate for a half an hour or so, reset all the valves to the normal position and flush the system out via a sink or shower. You can buy a flush kit with pump, hoses and bucket on Amazon. Maybe at your hardware store too.

 

[judypilot]

Take a look at the picture in my first post. The two copper pipes under the unit are the inlet and outlet. The isolation valves on them are two way, and there are garden hose fittings on the valves so that you can connect a couple hoses, one going to a small pump inside a bucket filled with descalant, and another being the return line. You let it recirculate for a half an hour or so, reset all the valves to the normal position and flush the system out via a sink or shower. You can buy a flush kit with pump, hoses and bucket on Amazon. Maybe at your hardware store too.

Thanks! I missed the picture first time around.

 

[Sac Arrow]

We're at roughly six months since installation, and the first warranty call was made. The PRV that vents water to the outside in an over pressurization was leaking from its assembly joints. Not much, just weeping. I noticed a ton of scale around it and found it was wet. It got fixed.

So far pretty happy. The hot water is nice.

I'm happy to get rid of of the tanked water heater. Two days ago, a house four houses down burned up because the water tank exploded and the gas fueled a big fire. Five fire engines were parked in the middle of the street, and an ambulance in front of my house.

 

[SoonerAviator]

We're at roughly six months since installation, and the first warranty call was made. The PRV that vents water to the outside in an over pressurization was leaking from its assembly joints. Not much, just weeping. I noticed a ton of scale around it and found it was wet. It got fixed.

So far pretty happy. The hot water is nice.

I'm happy to get rid of of the tanked water heater. Two days ago, a house four houses down burned up because the water tank exploded and the gas fueled a big fire. Five fire engines were parked in the middle of the street, and an ambulance in front of my house.View attachment 139393

Had a house directly behind us explode/catch fire about 3 years ago when one of their teen boys was using something flammable in the basement and managed to have the gas water heater ignite. Teens got out alive but burned the house to a total loss.

Spurred me to replace my 18+yr old water heater just as a safety precaution (and due to loss of heating capacity due to sediment.

 

[Flyhound]

We live in an area that is "overdue" for a magnitude 9+ subduction zone megaquake and and associated tsunami. We had planned for a tankless system in the house we were building, but we attended an "earthquake preparedness seminar" that convinced us to stay with a tank system. In a major earthquake like that, city water systems are likely to fail, both at the central facility and in multiple places in the distribution network. Wells may become useless due to widespread power outages. Having 80 gallons of potable water in a tank in our garage seemed like a really good idea while we tried to figure out what to do next. We installed a heat pump tanked water heater and it has been really efficient as well as providing emergency water storage.

 

[jesse]

Mine works great, I'd never go back to a traditional setup. The single on-demand boiler unit provides hot drinking water and is the heat source for my house and shop. My entire foundation has in-floor radiant heating. Additionally, the second story of my living quarters has forced air (which is also hydronic). All of that from one flame.

The on-demand combo boiler keeps the hot drinking water entirely separate from the heating water to avoid stagnant water bacterial concerns. The only place where the two systems interconnect is via a make-up valve that can be used to add more water to the heating system if needed. It has a one-way valve, and a traditional manual valve which I keep closed and have never had to use.

 

[pfarber]

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.

Installer error is very common. I installed two, one in my home and one in parents house (there were combo-water and hydronic heat).

One did wear out the burner can but that was a quick $50 fix. Both are installed over 10 years.

 

[midwestpa24]

Mine works great, I'd never go back to a traditional setup. The single on-demand boiler unit provides hot drinking water and is the heat source for my house and shop. My entire foundation has in-floor radiant heating. Additionally, the second story of my living quarters has forced air (which is also hydronic). All of that from one flame.

The on-demand combo boiler keeps the hot drinking water entirely separate from the heating water to avoid stagnant water bacterial concerns. The only place where the two systems interconnect is via a make-up valve that can be used to add more water to the heating system if needed. It has a one-way valve, and a traditional manual valve which I keep closed and have never had to use.

View attachment 139401

We are getting ready to build a new house and our plumber was trying to talk us into one of these. Call me old school, but with a background in building maintenance, I just see a maintenance headache. Computers, sensors, pumps, etc., all kinds of things to break. In my experience, when they do it will be expensive or unobtainable. We are opting for traditional tank water heater and furnace/AC. Properly maintained, a quality tank style water heater should easily last 10-15 years and is easily replaced. I just replaced the one in our current house that was over 20 years old. The key is not to buy one of the cheap ones from a big box store, spend a few hundred extra and get a goo Rheem or AO Smith from a plumbing warehouse. If it has a plastic drain, its not quality.

 

[jesse]

We are getting ready to build a new house and our plumber was trying to talk us into one of these. Call me old school, but with a background in building maintenance, I just see a maintenance headache. Computers, sensors, pumps, etc., all kinds of things to break. In my experience, when they do it will be expensive or unobtainable. We are opting for traditional tank water heater and furnace/AC. Properly maintained, a quality tank style water heater should easily last 10-15 years and is easily replaced. I just replaced the one in our current house that was over 20 years old. The key is not to buy one of the cheap ones from a big box store, spend a few hundred extra and get a goo Rheem or AO Smith from a plumbing warehouse. If it has a plastic drain, its not quality.

You're not going to get away from sensors and computers with a new tank water heater and furnace/AC. Those are the parts that will be unobtanium. As to the pumps and relays involved in my setup there is precisely zero chance they will ever become unavailable. It's all very standard stuff and completely interchangeable. Yes, parts of the combo boiler/forced air furnace/AC could one-day be unavailable, but that's just the same as your traditional stuff.

 

[SoonerAviator]

We live in an area that is "overdue" for a magnitude 9+ subduction zone megaquake and and associated tsunami. We had planned for a tankless system in the house we were building, but we attended an "earthquake preparedness seminar" that convinced us to stay with a tank system. In a major earthquake like that, city water systems are likely to fail, both at the central facility and in multiple places in the distribution network. Wells may become useless due to widespread power outages. Having 80 gallons of potable water in a tank in our garage seemed like a really good idea while we tried to figure out what to do next. We installed a heat pump tanked water heater and it has been really efficient as well as providing emergency water storage.

Well problem is solved with having a backup/portable generator, but that's a different discussion.

 

[Sac Arrow]

Just as an update, I decided the annual flush wasn't a big deal to do, and it wasn't. I got the kit from the Zon, and it included a couple right angle hose connections so it all worked out fine. I used the supplied cleaning solution in the recommended dilution, recirculated for 45 minutes. The hardest part was getting the lid off the bucket.

I was expecting the water to be more gnarly than it was - but there were white spots on the pump where it dried after I hosed it down, so I guess it must have done something.

 

[WJG-GMT-RootBeer]

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.

We have one---zero complaints or issues after many years---knock on wood.

 

[Stewartb]

Navien is a good manufacturer. A plumber friend installed one when the boiler component of my very expensive Lennox system failed. The Navien unit provided heat and domestic hot water and worked perfectly. When my hangar on-demand unit times out I’ll put a Navien in it’s place.

 

[Gary Ward]

I have been a LP gas supplier for 35 years.
I have fielded many calls( just hung up with another customer) from customers claiming that the pressure regulator is putting out low pressure causing problems with their tankless water heaters.
It's not the reg, it's the pipe size from the low pressure reg outside the home to the water heater inside the home. Most tankless I have seen are 199000 BTU. When they try to use 3/4 pipe that I see in so many pictures above and the same size they used on their tank water( that is 50,000 BTU) there isn't enough volume to keep your tankless water heater healthy. It will work at first, but will have a shorter life span.

Then add on other gas appliances the over all inlet piping coming into your home must be increased in size to be able to supply 200K btu to the tankless water heater.
It will also damage the house furnace because it is starving for gas too especially when the water heater is running when you have too small of piping.
Can't use the same size piping that you used for a tank water heater on a tankless water heater. People don't believe me but it's true. A typical house furnace is 60-80-100K BTU. So a 200K water heater needs a larger pipe going it than the furnace.

You need a large reservoir of gas right at the water heater inlet valve to supply 199K BTU to keep that water heater happy and 3/4 pipe is not going to do it with propane. Nat gas needs even larger piping.

The tankless water heater manufactures sell a reservoir that goes in the piping right in front of the gas valve to help have enough volume when the heater comes on. But if the over all piping is too small then you will still have problems.
Most of my customers have been putting parts into their 4-5 year old heaters before they call me because they don't have enough gas volume.

 

[brcase]

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.

no kidding my folk's water electric heater is probably 75 years old and still going strong.