Fairly Good Article

[A.D. Miller]

Product Pros and Cons: Tankless Water Heaters vs. Conventional Storage Tanks - Energy Efficiency, Remodeling, Water Heaters, Energy Star, Products - Builder Magazine (http://www.builderonline.com/energy-efficiency/tankless-water-heaters-versus-conventional-storage-tanks.aspx?cid=BLDR090922004)

[Jim Luttrall]

Good article, I spent quite a while trying to explain the pros and cons to a client just last night. I think I will keep this on file to share.
Thanks!

[Gunnar Alquist]

I have never seen a cost comparison for the life of the units. That, to me would be a deciding factor. The purchase and installation cost for tankless is 3-4 times that of a tank, but the lifespan for tankless is less than twice as long as a steel tank. Given its price tag, will tankless save money over the life of the unit?

[Ron Hasil]

I have never seen a cost comparison for the life of the units. That, to me would be a deciding factor. The purchase and installation cost for tankless is 3-4 times that of a tank, but the lifespan for tankless is less than twice as long as a steel tank. Given its price tag, will tankless save money over the life of the unit?
One advantage a tankless has in the life span part is when a part leaks, you can just replace that part. unlike a tank where you need a whole new water heater. So yes the install cost is a hard hit but down the road repairs will be much cheaper.

[A.D. Miller]

The only disadvantage I see to these units, which is still outweighed by their energy efficiency and lifespan, is the need for annual maintenance.:mad:

[Rick Bunzel]

Two other disadvantages of tankless:

Roller coaster effect - Unlike tank water heaters there is an initial delay once you turn on the tap. You can see this with an IR thermometer. Turn on the tap and you get the water in the line which may still be warm, then you get a slug of cold water and then you get water that is slowly coming up to the preset temp. Obviously the system cannot produce hot water instantly so you get this roller coaster temp swing which length is partially determined the distance from the unit.

No recirc system - Obviously you cannot recirculate the warm water (OK this is an energy waster) unless you add a tank to the system. I have seen builders do this to accommodate the longer plumbing runs in big ranchers.

I will have to replace my water heater in the near future and will stick with a tank. The ROI at this point is not great enough warrant the expense of going to tankless. Going with a smaller but quick recovery Energy Star water heater just make better sense

//Rick

[Jim Luttrall]

The only disadvantage I see to these units, which is still outweighed by their energy efficiency and lifespan, is the need for annual maintenance.:mad:

Eternal hybrid: the world's first and most advanced hybrid water heating system (http://www.eternalwaterheater.com/)

Says they are maintenance free since the water does not go through the interior of the pipes.
Might be a better mouse trap... I did not see the price though.

[Brandon Whitmore]

Can a tankless system be installed on an older house with a 1/2" service? It looks like the incoming/ outgoing connections are for 3/4" pipe, and heard or read something about a min. flow requirement.

Another pro of the tankless systems is the tax credit right now.

[Ron Hasil]

Use your tax credit on new windows or a furnace, Do not waste it on a tankless water heater.

[Brandon Whitmore]

Use your tax credit on new windows or a furnace, Do not waste it on a tankless water heater.

I'm installing a 95+ furnace this week-- just pulled the mechanicals for a furnace and water heater install. I was going to go tankless. I guess I need to read up more on tankless.........

[James Foy]

Most of the tankless water heaters I've seen start around 110,000 btu/h and go up to 180,000. 3/4" Pipe is the minimum when you calculate for developed length of the gas supply pipe. I've seen some where it needed to be 1.25" in order to supply everything else in the house before it got to the tankless on the far side of the house.

Also there is no mention of solar water heating in the article, though you could follow some links, but these will take even more space as you generally need another tank for the heat exchanger. The plus is these use very little fuel at all, and are especially effective on houses using electricity to heat the water.

[Brandon Whitmore]

Most of the tankless water heaters I've seen start around 110,000 btu/h and go up to 180,000. 3/4" Pipe is the minimum when you calculate for developed length of the gas supply pipe. I've seen some where it needed to be 1.25" in order to supply everything else in the house before it got to the tankless on the far side of the house.


Thanks James,

but...... I should have mentioned my question was for the water connections......

[Ron Hasil]

Thanks James,

but...... I should have mentioned my question was for the water connections......
The manufactures recommend ¾" water supply pipes. The minimum flow rate is 0.5 gpm Also be sure your gas s piping is sized to handle the 199K BTU's of a tankless water heater as well. Check to see if the gas supply pipe has other things drawing off of it. Plus check to see if your gas meter can handle the total BTU load of your home.

[James Foy]

Just like the tank water heaters, tankless require 3/4" water supply connections. You might check the IPC and see if 1/2" would supply all the hot water a building requires, but lack of cold water supply could have some ugly results. Think about a radiator with our enough water.

[Brandon Whitmore]

The manufactures recommend ¾" water supply pipes. The minimum flow rate is 0.5 gpm Also be sure your gas s piping is sized to handle the 199K BTU's of a tankless water heater as well. Check to see if the gas supply pipe has other things drawing off of it. Plus check to see if your gas meter can handle the total BTU load of your home.

Thanks Ron.


You might check the IPC and see if 1/2" would supply all the hot water a building requires, but lack of cold water supply could have some ugly results


The home is older, so the installation would be a retro- fit. I have no plans on replacing the service. At least not 'til I do an addition down the road........

[Dennis Webber]

One advantage a tankless has in the life span part is when a part leaks, you can just replace that part. unlike a tank where you need a whole new water heater. So yes the install cost is a hard hit but down the road repairs will be much cheaper.
In these articles, I keep seeing where tank-type water heaters only last 5-7-10 years.

I find that hard to believe. I can't ever recall seeing a water heater only lasting 10 years. In our subdivision, which was built in 1978-80, I haven't found anyone who has replaced their gas or electric water heater. Not one. My gas water heater is the same one that was installed when the home was built in 78. That's 31 years in my case.

My son-in-law's tank gas water heater was leaking when he bought his house, and that house was built in 1972. We went up to Sears, bought a new one on sale for two something and had in installed in an hour. (Can't do that with a tankless).

My parents water heater lasted nearly 40 years.

So where did this 5-10 year lifetime ever come from? Is that all the rest of you are getting from your gas water heaters?

I agree with the other gentlemen who stated that most of what we are reading on this subject is hype from the tankless industry.

They have a place, but I'm not convinced that they are so much better. (After all, you can buy a gas tank-type water heater now that only loses 1 Btu/H in standby losses. AND, you can always wrap an additional layer of blanket insulation over the old gas water heater to improve it's efficiency).

[James Foy]

I replaced the original water heater of my 1973 home last year, so it lasted 35 years. I think perhaps the new ones are designed to last only 7-10 years, as opposed to the old units which were designed to last for 12-20.
There are a number of changes that have taken place over the last 20 years. Maybe the lightweight parts are part of the issue. Maybe it's chemicals in the water. I know the new tank felt about half as heavy as the old one, and there wasn't any sediment in the old one when I removed it. Maybe it's a change in the attitude of the manufacturers and people building the units. Or perhaps, it a combination of all of the above.
I'm curious if anyone out there has any insight into the change in water heaters.