Learn me: Tankless water heaters?

We’re on the home-stretch on the “creekhouse” (1,000 square foot house. Built in early 1900’s)

While shopping for water heaters, it occurred to me that going tankless would save us a bunch of much needed space.

I’m trying to get everything we can at the local HD. They have This one in stock. What do y’all think? It’s me, my wife, and 2 kids, 7 & 4yo. One bathroom. Two showers in the morning, two in the evening.

Also, is installation any more challenging than a standard water heater?

THANKS!

No clue on the model or install, but just make sure you know the downfall of tankless: You have to wait for hot water. I lived with one for 3 months (college summer sublease). I'd turn on the shower, then get undressed and brush my teeth. If I was washing dishes, it was turn on the faucet, go to the fridge and put things away, and 45 seconds later get to actually washing the dishes. Not a big deal except for washing hands, and for a vacation home not an issue at all. The flipside is that you have unlimited hot water, and there is nothing to blow so when it fails, you don't have a basement/kitchen/crawlspace that you need to dry out. 

Downside, wait for hot water. 

Upside for an occasional use home, you are not paying to keep water warm during the weeks you're not there. 

I researched those a year or so back in planning for a water heater replacement. The main concerns I had are:

Do you have panel space for 3, 40 amp breakers?

They can be a little funky. Running out of capacity under high load. Water too hot, too cold. Low flow.

Inlet water temperature is critical. As incoming water temps drop, outgoing volume falls significantly. Winters you may only be able to run one outlet.  See the chart.

The gas versions are supposed to work better due to the BTUs they will put out. But they are also very expenisive.

Also the average water temp map is pretty optimistic. I check my water temps down here on the coast. Winter temps are about 45-55 degrees. Now is the time to test them. 

Feck. I was hoping this would be the “easy button.” This will be our full-time house for a year or so while we build. Then a “crash pad” for friends & family. Might still be the way to go. Good to know on the breakers. Also, we *could* go gas. That’s what I’d planned on doing for the traditional tank heater. Only thing that sucks is we’d be running of the “submarine...” which reminds me, I gotta call those guys....

Minimum flow turn on rate is something to consider. 0.5 gpm is quite a bit of flow to rinse your fingers quickly but can be the min flow rate to fire the water heaters. Also the minimum goes up on the larger units that can feed a shower and dishwasher at the same time.

I have considered a decent size instantaneous water heater feeding into a 5/10 gallon water heater. Then you always get hot water at any flow rate, but now you have two units that could fail but you have a bit of back up.

Having a circulator will alleviate the wait on the delivery of hot water, but verify use with the water heater mfg.

RossD said:

Minimum flow turn on rate is something to consider. 0.5 gpm is quite a bit of flow to rinse your fingers quickly but can be the min flow rate to fire the water heaters. Also the minimum goes up on the larger units that can feed a shower and dishwasher at the same time.

I have considered a decent size instantaneous water heater feeding into a 5/10 gallon water heater. Then you always get hot water at any flow rate, but now you have two units that could fail but you have a bit of back up.

 

 

I think they have hybrid water heaters now that basically do this in one unit. 

mtn said:

No clue on the model or install, but just make sure you know the downfall of tankless: You have to wait for hot water. I lived with one for 3 months (college summer sublease). I'd turn on the shower, then get undressed and brush my teeth. If I was washing dishes, it was turn on the faucet, go to the fridge and put things away, and 45 seconds later get to actually washing the dishes. Not a big deal except for washing hands, and for a vacation home not an issue at all. The flipside is that you have unlimited hot water, and there is nothing to blow so when it fails, you don't have a basement/kitchen/crawlspace that you need to dry out. 

 

 

I have two tank type water heaters. You describe to a T what is required to get hot water out of them too.  

You see water in the lines cools down quickly. The further from the water heater  the faucet is the longer it takes to run out that cold water and get hot!  Yes insulation will keep the hot water warm for a while but not for very long. 

If you are willing to pay the price you can get recirculating hot water nearly instantly. But your energy bill goes up dramatically.  It doesn’t matter  if it’s tank type or tankless. In addition to the cost of constantly reheating water, you have a pump that is always on to pay for.  

Bottom line?  Tankless can save you money on energy bills but has a learning curve.  You need either a really good filter system. Or need to service it frequently 

Come to think of it, that applies to both types of water heaters.  

With regard water heaters in general.  Nearly every brand makes price point water heaters and better quality water heaters. It would be wonderful if the price you pay had some relationship with quality. It doesn’t. Plus last years/ months/ weeks  great deal  may have better or worse components. 

Consumer Reports  is you only real source of unbiased information. 

I have a Rinnai tankless that runs my whole house, and I love it.  Mine is gas fired, though, not electric.  I can't vouch for large electric ones as far as expense and response time goes.  The gas fired one is noticeably (but not radically) cheaper to run than our 10-year-old tanked gas heater was.

The tankless gas unit in the basement gives me hot water at the second floor shower in about 90 seconds.  That's maybe 30 seconds slower than the old tanked unit used to respond.  But the real joy is that you can basically take an infinite shower and it easily keeps up.  When we had 4 people in the house, that was a real bonus.

They are programmed to ignore small demands for hot water.  Most people leave their single-lever faucets set in the center and just tunr them on and off.  If the tankless unit responded to this small demand, it would fire up every time somebody ran any water at all.  So if you really want hot water, you have to run it fairly hard or fairly hot to get its attention.  But once you have it running, a continuous smaller demand will keep it going.  It takes a week or two to adjust your usage pattern to work with it.

But I have no complaints, and wouldn't go back to a tanked heater.  The Rinnai is about 10 years old and has never missed a minute of service.

I have tankless that runs my whole house. 3 bathrooms, fully functioning family of 5. Absolutely love it. Mine is installed outdoors on side of house. Temps are BURNING hot. No issues.   The furthest POINT from the house, I have to wait about 37-40 seconds for heat up (which is our kitchen). 

Our bathrooms about 15-17 seconds of wait time for hot water. 

Aboslutely love it. Never will go back to standard water heater again. 

Infinite water heat - love it.

Hmmm.. what if you had multiple smaller electric tankless heaters serving separate demands / rooms? You could locate them very close to or even in the room with the hot water need. Would that make any sense? I see this heater is rated for 5 gpm flow, what if you had one 1.5gpm unit (Eco 11) in the bathroom and one 1.5gpm unit in the kitchen. Only two 60 amp breakers instead of three 40 amp. Hot water would happen sooner since there wouldn't be much pipe between you and the heater, the plumbing would be simpler at the cost of electrical wiring.

Go gas, go small, and check your payback time on tankless vs tanked.

dculberson said:

Hmmm.. what if you had multiple smaller electric tankless heaters serving separate demands / rooms? You could locate them very close to or even in the room with the hot water need. Would that make any sense? I see this heater is rated for 5 gpm flow, what if you had one 1.5gpm unit (Eco 11) in the bathroom and one 1.5gpm unit in the kitchen. Only two 60 amp breakers instead of three 40 amp. Hot water would happen sooner since there wouldn't be much pipe between you and the heater, the plumbing would be simpler at the cost of electrical wiring.

 

My neighbor did that. He has same issue as me, as the kitchen is furthest, it takes the longest for water to travel. HOWEVER, instead of another tankless heater, there is some kind of diverter valve thing or some inline tank he installed, which makes it go right away to kitchen, and his problem is solved.  Waiting 40 seconds in the kitcen doesn't bother me enough to do all the work h did. 

What's the gallons per minutes needed for a decent shower to wash but not  like a high powered massage shower....

Starting with 45 degree water ?

 I was thinking a larger one for the bathroom and a small one under the sink for dishes , 

I doubt you could fill up a bathtub with one of the medium size electric heaters , or it would take a long time.

chaparral said:

Go gas, go small, and check your payback time on tankless vs tanked.

It’s less about saving money, and more about saving space. Right now there’s a huge square water heater eating up a big chunk of space in the kitchen. The plan was to put a standard water heater in one of the two master bedroom closets - directly behind the shower, but it’d be a tight squeeze and eat up closet space. 

The tankless would go in the same spot, so literally inches from the shower.

You should also consider the mineral content of your water supply. If you have hard water the longevity of your heating element becomes a problem. 

We had a tankless on the old house, installed it when we did the repipe.  A few random thoughts:

The biggest wins are that it takes up less space and you get infinite hot water.  No more cases of your teenage daughter taking a really long shower and using up everything in the tank.

Downsides are that it's more expensive, you wait a bit more for hot water, and it usually requires a different vent than a traditional water heater.  It's either too hot or not hot enough or something, I forget which.  Also, because it needs all the energy at the same time, you'll need a bigger gas line running to it -- ours was 1.25 inches, IIRC.  I'd never go electric on something like that.  Another downside is that since the brains require electricity run you don't have hot water when the power is out, even for a gas unit.  (I guess you could use a UPS).

The biggest downside is that, according to the plumbers I've talked to, when they break they tend to be down for a long time.  Traditional water heaters are simple, easy to troubleshoot, and the parts are in stock at the store down the street.  Tankless units are a lot harder to troubleshoot and require parts that take several days to order, during which time you've got no hot water.  The new house has a traditional tank for this reason.

As for energy savings -- that's a fantasy.  You'll never pay back the additional purchase/installation cost through lower monthly energy bills before the tankless needs replacement.

Oh, it also needs to be descaled annually.  Install it with the service valves, get 5 gallon bucket full of white vingegar, a pond pump and some hose remnants, disconnect it from the water system, turn off the gas (so the burner doesn't light) and pump the vinegar through it for half an hour.

If you live somewhere that it doesn't get that cold, you can mount it on an outside wall.  Simplifies the venting, saves lots of space, and makes the descaling process less of a mess, but you need to run more pipes.

I installed a Rinnai gas tankless and am VERY happy with it. Initially we got "cold slugs" (Google it). Those result from someone turning a faucet on and off in short cycles, such as rinsing dishes, and the tankless not firing off. Then someone in the shower suffers a 10 second cold blast because the cold slug is trapped between hot sections. The accepted solution, which I installed, is a small 3-5 gallon tank water heater next to the tankless that swallows the small amount of cold and mixes it with 3-5 gallons of hot. You never see the cold slug. Yes, this means another device, but the fact that I can shower 6+ people in a 2 hour period on Sunday morning makes it work for us. Also, the small electric water heater almost never has to fire off because it is fed hot water from the tankless.

Having experience tank-less heat with my inlaws, have you considered having a smaller unit at each faucet?  The one at my inlaws just does the shower, and it does it pretty darned well.

And it's 120V instead of some kind of hardwire set up.  

due to the way this house was built, the heater and hotwater heater are under the bedrooms, but the kitchen is at the total opposite side of the house. While even with a tanked heater, it can take a moment or two to get hot water, It takes over a minute to get hot water to the kitchen. I am planning on a small "instant heat" tankless under the sink just to make up for it.

Had one at our last house. I really liked it except we had hard water and you had to make sure it was staying clean. The hard water deposits would mess it up. It was a bit of work to keep it running well

BlindPirate said:

Had one at our last house. I really liked it except we had hard water and you had to make sure it was staying clean. The hard water deposits would mess it up. It was a bit of work to keep it running well

Yeh but wouldn’t that also be true of a tank type?  I used to flush my tank type at my other house with bad water ( high Iron and calcium) once a month and replace water filters every other week not to mention replacing the sacrificial anode annually. 

lateapexer said:

You should also consider the mineral content of your water supply. If you have hard water the longevity of your heating element becomes a problem. 

 

I believe you are supposed to flush/clean them occasionally (depending on how hard your water is). I have heard once a year.  

frenchyd said:

BlindPirate said:

Had one at our last house. I really liked it except we had hard water and you had to make sure it was staying clean. The hard water deposits would mess it up. It was a bit of work to keep it running well

Yeh but wouldn’t that also be true of a tank type?  I used to flush my tank type at my other house with bad water ( high Iron and calcium) once a month and replace water filters every other week not to mention replacing the sacrificial anode annually. 

Tankless heaters suffer from scale at a much higher rate than tanked ones because they have much more internal surface area (that's the point of a heat exchanger) and thus smaller passages that clog up much more easily.