hot water system

[Pete Dorr]

We are going to replace our hot water heater. We live in Massachusetts. We use natural gas as fuel. Our choices are:

- hot water tank which is pretty standard in the US (at least in New England)

- tankless system which is gaining popularity here and I hear is the standard in Europe

I believe the tankless system is more efficient but at a higher initial cost.

I also hear that the tankless system can't really keep up with multiple people showering at same time.

I'm leaning toward tankless just because it's more enviro-friendly.

Is anyone in the industry that can comment on why we should go tankless ?

Thanks
Pete

[Canoez]

My in-laws have tankless systems in their homes which heat on-demand. Just anecdotal, but I've never had an issue with running out of hot water at any of their houses. Pressure drop causes the burner to kick in and they just heat water as needed.

[rbgarr]

I'm not in the industry but one reason we didn't go tankless is that the unit (at least the one recommended) needs to be fairly close to the shower, thus needing a long gas pipe if your shower is on the second floor. I hope I wasn't getting a bad 'explanatin' from the plumber.

[MiddleAgesMan]

When I built my new master bath 6 or 7 years ago I chose a high capacity tankless system--a Takana or Tanaka...some such name. It could handle the tub and shower at the same time but not much more.

I was very pleased with my choice until a couple months ago when I stepped into the shower and got blasted by cold water. Something in the unit had failed. I could have tried a pro repair but since the things are so rare I figured he'd probably scratch his head about as much as I so I went to the maker's website and followed their troubleshooting tips. The most obvious and easiest component to replace was the electronic spark controller. I ordered the part and put it in without success. More troubleshooting and help from a tech over the phone and we finally came to the conclusion it would be best to just replace it. They offered a $700 trade-in on a $1500 new one. Since I live alone and have another shower available I haven't done anything with it yet.

The conventional gas water heater that was probably original to this 40 year old house is still going strong.

[JimConlin]

In new work, i'd think that the fact that you don't need to pipe hot water to the bathroom would partially offset the other installation costs of a point-of-use water heater.
What gas piping materials are acceptable these days? Has PEX been adopted in that application yet? Certainly a fifty foot run of black iron pipe will drive the installation cost up.

[Torna]

Trickier than running the gas line to a remote installation is venting the unit (aka chimney). When they're working to try to keep up with both a shower and a tub fill, there's a BIG fire going in there. I don't think that they're made so that they can be vented with plastic pipe out through the wall (like many a condensing furnace these days), but rather need a proper chimney/stack/vent. (If you find that I'm wrong, please post here as I would be very interested)

Presumably your existing gas HW heater has a proper chimney setup, so replacing it with the on-demand type in that location should be viable. But putting it upstairs behind the shower/tub may be nigh impossible.

my 2c
-leif

[Lew Barrett]

If it were me starting over, I'd think tankless systems are the way to go if you can fit them into your program. Why store heated water to be re-heated 24/7 on a thermostat? How often does more than one person take a shower at a time in your place anyway? And, unless you keep a large tank, a storage tank will have it's own issues in those situations, including running out in the middle of the third person's shower, which would be mine after my wife and daughter had their way. A fast recovery tankless system is the way to go. This sort of re-thinking seems like a sign of the times.

[Noah]

One thing to keep in mind with hot water is personal habits - sometimes an efficiency change doesn't change the total energy consumption.

IE, a Family replaces their high-flow shower head with a 2gpm head, and they expect to see their hot water bill go down and it doesn't - before they would take a shower till the hot water ran out, and now they do the same thing - only the shower is twice as long.

I know that some of the efficiency of a tankless unit can be lost if you are prone to taking very long showers that might have previously been limited by the amount of hot water available.

Just something to think about.

[paladin]

The problems come with the installation and venting. When Irina and I built the new place in Odessa we had the instant on European type water heater installed. We had to redesign the entire apartment around it. Rules specify that the gas pipes must not be behind any panelling or wall, they must come directly thru the wall from outside to the inside wall for safety reasons, then the water pipes must lie exposed on the wall surface, so we had to reposition the bathroom/showers and kitchen...and so on.......then the boys bathroom and showers necessitated relocation of bedrooms. In the end I used a double system with a timer, so that we had a small electrically powered 8 gallon system more or less in parallel so that we had hot water in the bathrooms for short times and didn't have to run cold water for 10 minutes for it to get hot....

[ssor]

They also make condensing water heaters.

[sv Lorelei]

When we built the house here we put in point of use electric units. Not a perfect solution and the units available in Europe (where we'd first gotten the idea) are more flexible, they still represent a significant energy savings over keeping a tank full of water hot in the basement. Problem being that they can't handle a high flow shower system and there are only two heat settings so seasonal adjustments are required.

[J P]

If electric is an option check out the little Seisco tankless units.

http://www.seisco.com/index.html

There's some good info on that site.

[Tylerdurden]

I have been installing these in commercial applications with no issues and good reliability

http://www.foreverhotwater.com/

[The Bigfella]

We've been on heat pump hot water since 1993. Very cheap, very green.

[Tylerdurden]

We've been on heat pump hot water since 1993. Very cheap, very green.

Heat pumps are useless up here in New England and the ground loops are not much better. The southern states here are more suited for it.

[The Bigfella]

Yeah - not too good in cold winters eh?

[Concordia 33]

I'd reccomend boilermate. They use the hot water from your boiler to heat your domestic hot water. Because there is no fire chamber or flue, they can be super insulated - they lose less than one degree of water temp per day! They are reasonably priced at Home Depot, easy to install, and last a very long time - no tank corrosion. From what I have read, they provide more than enough hot water while providing the most energy efficient option.

[seedy]

There's a Tanaka (?) in the house I'm renting now, which is a ranch, but the kitchen sink is a long way from it (up, over, around, over some more, then down, over, and finally up). If I draw hot from that sink, I can hear the burner come on, just takes ages to get actual hot water. but it would take just as long from a tanked heater.

The disadvantage to tankless that bothers me the most is that the flow needs to be strong to keep the burner running, so no trickling hot out the showerhead to shave with. A slight difference in pressure can be a real wake-up call.:)


I'm not in the industry but one reason we didn't go tankless is that the unit (at least the one recommended) needs to be fairly close to the shower, thus needing a long gas pipe if your shower is on the second floor. I hope I wasn't getting a bad 'explanatin' from the plumber.

[Paul Girouard]

Tank-less with a recirculation loop. There's a cross over value that , via a small pump , pushes the "cooler" water back into the cold water side allowing hot water to be right at the value.

We've had 10 or so installed in the past 6 years or so . Every ones ( home owners) been happy with thier systems. The sub use Ranii (sp) brand heater.

[Canoez]

Trickier than running the gas line to a remote installation is venting the unit (aka chimney). When they're working to try to keep up with both a shower and a tub fill, there's a BIG fire going in there. I don't think that they're made so that they can be vented with plastic pipe out through the wall (like many a condensing furnace these days), but rather need a proper chimney/stack/vent. (If you find that I'm wrong, please post here as I would be very interested)

Presumably your existing gas HW heater has a proper chimney setup, so replacing it with the on-demand type in that location should be viable. But putting it upstairs behind the shower/tub may be nigh impossible.

my 2c
-leif

They did an installation on "This Old House" with a tankless system. It scavenged so much heat that they were able to use PVC for the exhaust.

[Captain Blight]

I know a guy who installed a tankless (actually two, one for the upstairs and one for the downstairs) system; but he kept his old tank, reasoning he was using it as a holding tank to get groundwater up to ambient indoor temp. He's had no problems (but he's only been running this system for a few months, and his daughter is only 8... I tell him to wait a few years...).

[Gary E]

They did an installation on "This Old House" with a tankless system. It scavenged so much heat that they were able to use PVC for the exhaust.

Sure about that??

I have seen the same shows where they install the tankless units and it has 2 pipes ..one inside the other, The inside pipe is the exhaust and the area between the outside pipe and the inside pipe is the fresh air intake. It's done that way for 2 reasons, the hot exhaust gas is HOT.. REAL HOT,, and the unit needs fresh air for the burner...

[Canoez]

Sure about that??

I have seen the same shows where they install the tankless units and it has 2 pipes ..one inside the other, The inside pipe is the exhaust and the area between the outside pipe and the inside pipe is the fresh air intake. It's done that way for 2 reasons, the hot exhaust gas is HOT.. REAL HOT,, and the unit needs fresh air for the burner...

Yep. I don't recall seeing a separate pipe or duct for fresh air intake, but I'm sure it was there. IIRC it was an episode where they renovated a barn or garage for this person's retired parents to live in. The mechanicals for this small home were mounted on a wall in the downstairs bath. And no, the exhaust gas was cool - Rich Trethewy put his hand on the thing. There was an pretty well designed heat exhanger which was a serpentine thing that basically scavenged the heat from the combustion. He was impressed at how efficient the thing was.

[Gary E]

http://www.foreverhotwater.com/operate.php

Hit the Gas and Air Flow button

You'l see the cool air coming down into the unit and the HOTTer'n he!! air going up
Do you think ther'r in the same pipe??

[py]

Hey bigfella, I'd be interested in more info about the heat pump option. We get down to about 0degreesC overnight in winter here. I've seen these advertised on ebay out of victoria with claims that they are good down to -10C. How cheap to run? How fast to recover after the 4th kid has his long hot shower on washing day? We are presently on a J tarrif (half price off peak) electric storage system. Been thinking about solar. The ebay dudes have a deal with 3 340 litre units for a shade under $3K. (Or one unit for $2800). And I think there may be a gov't rebate to replace an existing electric unit-so it kinda looks like a good option.
Thanks mate

[Canoez]

http://www.foreverhotwater.com/operate.php

Hit the Gas and Air Flow button

You'l see the cool air coming down into the unit and the HOTTer'n he!! air going up
Do you think ther'r in the same pipe??

Gary - Not for those guys, but there are units with PVC intake AND exhaust here (http://www.tanklessdeals.com/navien-tankless-water-heaters.htm) (Separate or counterflow pipes...)

There are many more out there, too.

Here's one from Noritz (http://www.noritz.com/homeowners/products/view/0841_series/):

0841 Series
PRODUCT INFORMATION:

NEW MODEL FOR 2008!
Noritz is proud to introduce our tankless condensing heaters, the next generation in tankless technology. This innovation utilizes a dual heat exchanger - a fusion of stainless steel and copper heat exchangers. The stainless steel component captures the residual heat from the exhaust temperature to preheat the incoming water before it runs through the main copper heat exchanger. This results in dramatic reduction of carbon dioxide and increases the heater's efficiency level to over 93%! Another benefit of this technology is lower exhaust temperatures, which means less costly PVC can be used for its venting.

[blacksmith]

Did I read someplace that the tankless heater warrantee is void if you're on well water?

[farwesthoops]

My experiences with tankless are a dozen years with a Paloma Tankless in my house (complete with children)in SE Alaska and then I lived and worked 7 years in Europe where tankless units are everywhaere. I think they are great and very functional.