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tankless water heater
Old 11-07-2012, 07:37 AM   #1
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tankless water heater

My son is going to install a water heater and was thinking of a tankless natural gas water heater to save space and run more efficiently. I have no experience with tankless and would be installing it myself. I was wondering if anyone here has dealt with this subject and the pros and cons of the tankless heaters or the installation process. any info would be appreciated.
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Old 11-07-2012, 07:40 AM   #2
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Search on the forum for 'tankless' and you'll come up with at least a dozen threads on the installation, care, feeding, and relative merits of the appliance.
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Old 11-07-2012, 09:56 AM   #3
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I installed an LP gas tankless water heater last year. I thought it would be straightforward, it was not.

1) vent ducting had to be replaced to larger 5" diameter. It was pain to do that with time spent in attic and on the roof.
2) the tankless water heater needs a minimum flow to heat water, difficult to adjust flow switch setting to allow it to produce hot water at all and not have too much hot water. The bathroom faucet was of a type that automatically adjusted hot and water flows to maintain temperature. This feature would fight the minimum flow switch in the water heater and result in hot water suddenly shutting off in the middle of a shower. This was not acceptable.

If you are thinking of an electric one, remember that you may need up to 100 amp service dedicated tot he heater by itself.

Installing a tankless water heater is not for the faint of heart. If you can install a gas or LP heater outside, it would simplify things.

I just removed the tankless one and had a 40 gallon tank heater installed.
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Old 11-07-2012, 09:56 AM   #4
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My sister has one and she loves it. Sorry, that I don't have any more experience than that.
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Old 11-07-2012, 10:23 AM   #5
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I'm curious how much energy savings people really experience.

Water heaters are well insulated these days. The savings from doubling the insulation is minimal. The real energy cost comes from heating the water in the first place, keeping it warm is minor.

Picture riding a bike from 60' sea level up to 135' sea level in a short time, and then just coasting along at 135' for a while. It's kinda like that (substitute degrees Fahrenheit for feet sea level).

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Old 11-07-2012, 12:03 PM   #6
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[QUOTE=gsparks2;1246364]I installed an LP gas tankless water heater last year. I thought it would be straightforward, it was not.

1) vent ducting had to be replaced to larger 5" diameter. It was pain to do that with time spent in attic and on the roof.
QUOTE]

+1 Depending on the model you opt for, the more efficient ones require a larger vent stack. That is certainly a PITA from my viewpoint.
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Old 11-07-2012, 04:19 PM   #7
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I have a Takagi propane tankless water heater that not only provides our domestic hot water but also powers the radiant slab and the hot water baseboard upstairs. The unit is a bit bigger than a 30-pack. I have been very pleased with it.

Installation was easy - I just wrote a check.

Seriously though - I don't think the installation was particularly difficult. However, I would think you would need to be a licensed electrician for an electric unit or propane/NG certified for a gas unit.

Its hard to tell how much they save since we are doing more than just domestic hot water with it.
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Old 11-07-2012, 05:10 PM   #8
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I purchased one from home depot. They came, installed it, and that was that. have loved it ever since. Only PIA was that I had to have 2 separate installers come out. One for mechanical and the other for electrical.

I say go for it. I love mine
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Old 11-07-2012, 05:24 PM   #9
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A tankless water heater will save space. I don't think they save much energy in most applications (not much is lost via a traditional tank, and in some cases the greater heat exchange area available with a tank allows a given amount of gas to more efficiently heat water). Also, tankless units require a minimum flow rate to start heating the water, a unit with a tank will provide a trickle of HW if desired. Also, if you have hard water or other issues, water with a high or low pH, etc, then it's likely any water heater will suffer a shorter life. I'd rather replace a $300 water heater in 10 years than a $1000 tankless unit at the exact same interval--or less (more things to go wrong with the tankless unit).

A bonus: We've had recent threads on natural disasters, etc. Having 50-80 gallons of water always available in an emergency could be handy.

It's just an appliance to do a job. Put the money saved by not buying/installing a tankless unit in an the ol' retirement nest egg. With any luck just the growth of the money in the 12 year expected life to the water heater will be more than enough to pay for the next "conventional" tank water heater. Repeat every 12 years--free hot water heaters for life by not buying a tankless unit.
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Old 11-07-2012, 05:34 PM   #10
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Here's what consumer reports said:

Are tankless water heaters a worthwhile investment?

Quote:
... Some makers of gas-fired tankless water heaters claim their products can cut your energy costs up to half over regular storage heaters. So is it time to switch?

Probably not. .... But because they cost much more than storage water heaters, it can take up to 22 years to break evenólonger than the 20-year life of many models. Moreover, our online poll of 1,200 readers revealed wide variations in installation costs, energy savings, and satisfaction.

Here's what else we found:

... inconsistent water temperatures were a common complaint among our poll respondents. When you turn on the faucet, tankless models feed in some cold water to gauge how big a temperature rise is needed. If there's cool water lingering in your pipes, you'll receive a momentary "cold-water sandwich" between the old and new hot water. And a tankless water heater's burner might not ignite when you try to get just a trickle of hot water for, say, shaving.

Nor do tankless water heaters deliver hot water instantaneously. It takes time to heat the water to the target temperature, and just like storage water heaters, any cold water in the pipes needs to be pushed out. And tankless models' electric controls mean you'll also lose hot water during a power outage.
-ERD50
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Old 11-07-2012, 05:41 PM   #11
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The only advantage I see with tankless heaters is that they take up less room. Their supposedly ability to supply unlimited hot water is a drawback to me. Back when my daughter lived with us, she would stop showering (or was it shaving her legs) when the water ran cold. And she managed to use up two tanks of 50 gal each (I had a solar water heater back then). I cannot afford the unlimited hot water!
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Old 11-07-2012, 05:44 PM   #12
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I looked at tankless when I was getting ready to replace my old 40 gallon natural gas heater. I just couldn't see the payback or benefit. I picked up a new heater off Craigslist for $125 (guy bought the wrong one and couldn't return it). My gas bill with hot water, stove, clothes dryer and BBQ runs about a buck a day, even with a return circuit that always keeps hot water at the farthest tap.

The tankless would just about have to run for free to give a reasonable payback.
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Old 11-07-2012, 06:03 PM   #13
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For us it had a quick payback in both fuel and water usage.
That's because our old tank water heater was in the garage - then ran uninsulated pipes through a concrete slab, then up to the attic, then to the upstairs bathrooms, and finally to the kitchen sink.
So it was almost 5 minutes from turning on hot water to getting hot water. That's a lot of cold water flowing down the drain. We live in a semi-desert (San Diego) that experiences a lot of droughts... so this was a big deal.

Now it's mounted on the outside of the kitchen... so about 20 seconds or less to get hot water at the kitchen sink, and about 90 seconds to get to the upstairs bathrooms on the NEW insulated pipe runs.

Obviously installation was a bit more complex since we were changing locations. But this was done in conjunction with other long term remodel goals.

We no longer have to overcome the thermal mass of a cold slab... that is huge.
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Old 11-07-2012, 06:21 PM   #14
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We have a natural gas tankless hot water heater in our new townhouse. We've been there for two years now and we like it . It supplies all of our hot water needs and since we have a finished basement it is mounted on the wall in a closet which saves quite of bit of space and it's extremely quite.

Another advantage is you do not have to worry about a big leak in your tank that will flood your basement as happened once in our old house.

The only drawback is that with an electronic ignition it cannot be ignited manually so you don't have any hot water when you lose power.

If you decide to go with the tankless unit I highly recommend a professional installer.
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Old 11-07-2012, 06:48 PM   #15
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Quote:
Originally Posted by frank View Post
My son is going to install a water heater and was thinking of a tankless natural gas water heater to save space and run more efficiently. I have no experience with tankless and would be installing it myself. I was wondering if anyone here has dealt with this subject and the pros and cons of the tankless heaters or the installation process. any info would be appreciated.
On an episode of This Old House they replaced a gas water heater with a gas tankless one. The "omg" moment for me was when they decided that the tankless required a larger gas line into the house to meet the larger, but shorter lived, gas demand. Replacing the gas line into the house then required that the gas meter be replaced with a larger one. Maybe gas line capacity is not a common problem, but it might be worth figuring out whether your gas line is sufficient before purchasing anything.
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Old 11-07-2012, 07:49 PM   #16
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Another advantage is you do not have to worry about a big leak in your tank that will flood your basement as happened once in our old house.
But it is connected to a humongous 'tank' - your water supply. At over 5 GPM, a big leak would deliver that 50 gallons whether there is a tank or not. And a small leak would be the same either way.

A water heater should have a pan leading to a drain, so it usually isn't a big deal anyway.

-ERD50
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Old 11-07-2012, 08:51 PM   #17
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Quote:
Originally Posted by gromit View Post
On an episode of This Old House they replaced a gas water heater with a gas tankless one. The "omg" moment for me was when they decided that the tankless required a larger gas line into the house to meet the larger, but shorter lived, gas demand. Replacing the gas line into the house then required that the gas meter be replaced with a larger one. Maybe gas line capacity is not a common problem, but it might be worth figuring out whether your gas line is sufficient before purchasing anything.
Gas line capacity wasn't an issue for me - it used the same lines as our gas dryer = 3/4" or 1" black iron pipe - not sure which but it was one of those - 3/4" I think.
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Old 11-08-2012, 09:22 AM   #18
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(snip)even with a return circuit that always keeps hot water at the farthest tap. (snip)
Tell me more about this return circuit--I've never heard of them before. My bathroom is at the far end of the house from the water heater and I would like not to run lots of water down the drain every time I want hot water there.
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Old 11-08-2012, 09:58 AM   #19
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I have thought about installing a return line and a pump to save on the water I waste each time I want to get some hot water. A switch for the pump to turn it on when needed would mean that electric power is not wasted to keep the line hot all the time. I am patient and willing to wait a few tens of seconds for hot water.

The problem is my bathrooms and kitchen are so spread out that multiple circuits would be required, and there is no inexpensive way to install them without tearing up the drywall.

PS. I guess it is possible to use the cold circuit as the return line, but then the cold water line also gets hot. This gets tricky!

PPS. See: http://en.wikipedia.org/wiki/Circulator_pump
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Old 11-08-2012, 10:24 AM   #20
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I think the hot water delay is an about equal problem with either tank or tankless since it is a matter of getting hot water from the tank or tankless to the faucet (assuming that the tank or tankless are in roughly the same place in the building).

I placed the pex manifold about equidistant from the bathrooms and the kitchen sink and the run from the tankless to the manifold is ~15-20 feet. While I've never measured it I'm guessing it is ~1 minute between turning on the hot water faucet and hot water coming from the tap from a "cold" rest.

I don't think 1 minute is unusual, but it is still annoying. I have been considering putting in small electrical on-demand hot water heaters under the kitchen and bathroom sinks to have instant hot water. As I'm thinking of it the electrical unit would heat the water until the hot water arrives from the main system. Has anyone out there tried something like this?
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