What's new

tankless water heaters? (1 Viewer)

Craig Robertson

Supporting Actor
Joined
May 12, 1999
Messages
982
my conventional water heater is on it's last legs. anyone have any experience with tankless systems, like the Bosch AquaStar at Link Removed or any other product?
i'm looking for both good and bad.
Thanks!
 

Scott L

Senior HTF Member
Joined
Feb 29, 2000
Messages
4,457
I posted on this a loooong time ago so now the thread is deleted. The general consensus was that it's just not worth it because it feeds off the incoming cold water pipe to your house, meaning that whenever you use hot water your cold water pressure dramatically decreases. For members with families this wasn't a good thing but for couples or singles it wasn't so bad.

Hopefully they've come up with some new technologies since then.
 

Craig Robertson

Supporting Actor
Joined
May 12, 1999
Messages
982
it feeds off the incoming cold water pipe to your house, meaning that whenever you use hot water your cold water pressure dramatically decreases.
i don't understand how that is any different than a conventional tank based system. when i turn on the hot water now, whatever hot water i draw from the tank is simultainiously replaced by cold water drawn from the cold water supply.

either way, 10 gal of water out of the heater means 10 gal of cold water into the heater.
 

Scott L

Senior HTF Member
Joined
Feb 29, 2000
Messages
4,457
Yea but the tank doesn't get filled up as fast as its taken out. From what I understand a tankless heater is much more demanding on the water pipe to your house, designed for high output.

Hopefully someone who actually has one or has used one could tell you the pros/cons more.
 

Craig Robertson

Supporting Actor
Joined
May 12, 1999
Messages
982
the tank doesn't get filled up as fast as its taken out.
that statement is simply not correct. there is no provision for cold water to enter the tank slower than hot water is drawn off, it is the inlet cold water pressure that forces hot water out when you open the faucet.
 

JohnRice

Bounded In a Nutshell
Premium
Reviewer
HW Reviewer
Senior HTF Member
Joined
Jun 20, 2000
Messages
18,926
Location
A Mile High
Real Name
John
Yea but the tank doesn't get filled up as fast as its taken out
There may be some truth to this due to a little bit of flex to the tank, but I expect is it insignificant. I have noticed that the water pressure from the tank tends to be lower that the cold water. This may have something to do with it.

I have thought about one of these for my Darkroom simply to isolate the hot water supply to the Darkroom from the rest of the house. I have the impression they are generally best for areas where they aren't used a lot. Like in a vacation home. Also, all the ones I have ever heard of were electric. Maybe there are gas ones now. If you are looking to save money, a gas tank will probably still be less expensive to use than an electric tankless heater, particularly if you insulate it well and keep the temperature set at a reasonable level. I have mine set to 125 degrees, which is fine for anything other than the dish washer, so I just turn on the temp boost element on my dish washer.
 

Craig Robertson

Supporting Actor
Joined
May 12, 1999
Messages
982
Bosch has models available in electric, natural gas, or propane.

my current water heater is electric, but i have gas coming into the house. the water heater sits next to the gas furnace. the two most likely scenarios are replace with a conventional gas water heater or a gas tankless heater.
 

David Werner

Stunt Coordinator
Joined
Jun 30, 1997
Messages
191
I thought about going this route however if you have a family with a high demand for hot water it is best to have two of these units such as one for the Kitchen and bathroom and one for the Laundry and bathroom. The reason being is that the demand for the quantity of that high of temperature of water for the entire house typically exceeds that of one unit. I believe last I looked that multiple installations was on some of the manufacturers recommendations. I'm all for it, by the way I still can't figure out why (At least none I've seen) the manufacturers don't come out with a composite tank to avoid rusting the bottom! Let us know if you go the tankless route and how it works for you. Good-luck.
 

Craig Robertson

Supporting Actor
Joined
May 12, 1999
Messages
982
thanks, David.

as far as the composite tanks go, i think it's not so much rusting out as it is sediment build up. on a gas unit it builds up on the bottom and insulates the water from the flame, decreasing efficiency. on electric it does the same by isolating the water from the lower element.
 

Todd Hochard

Senior HTF Member
Joined
Jan 24, 1999
Messages
2,312
Personally, I'd go the gas tankless route. Gas is a more efficient way to heat water than electric.

The concept is perfect- heat ONLY the water you need. With a tank, a lot of the heat is wasted to ambient losses. This will place no higher water demand on your cold water system than any other hot water heating system (I'm not sure where the idea that it would came from).

Size it right- just like you would a tank. And I've seen some with long (15-20 years) warranties, so seek those out.

Todd
 

David Werner

Stunt Coordinator
Joined
Jun 30, 1997
Messages
191
I think the sacrificial (I think Magnesium)metallic rod should take care of that. Grant it the sediment will collect on the bottom but surely would not be as dramatic of rust effect as it would a composite base, efficiency aside. I know that we all practice our maintaince on our water heaters (Yeah right!). The thermo-coupler on our 40 gallon is going soon and this topic is sure tempting me to reconsider the tankless system, it's all about savings and makes perfect sense.
 

Scott L

Senior HTF Member
Joined
Feb 29, 2000
Messages
4,457
Ever wonder why most homes still use tanks if they cost more? When I worked in construction every new house for Ryan Homes had a hefty hot water heater that was a pain to haul into the basement. I wonder why they just didn't install 2+ tankless systems as David recommends. Maybe a deal with the electric company. ;)
We have a 52 gal and the bottom element seems to be dying out more often than it's supposed to (the tank is a little over 10 yrs old). Craig tell us what you think of your new tankless choice when you get the chance.
 

Todd Hochard

Senior HTF Member
Joined
Jan 24, 1999
Messages
2,312
Ever wonder why most homes still use tanks if they cost more?
Tanks are still cheaper than tankless systems. More heating elements in the tankless, plus there's that "it's a newer idea, therefore it has to cost more" thing.
Home builders are the biggest Luddites on the face of the planet. With a VERY FEW exceptions, the LAST place you will see new technology used is in the construction of a new home.
Crikie- you can't even get some builders to stop using stick framing in the termite-infested South.
Sorry, I digressed.:) I'm in the planning stages of putting together a custom home worthy of being built in the 21st century. The resistance from some at doing "common sense" things (like energy efficiency-) is ridiculous to me.
Todd
 

MickeS

Senior HTF Member
Joined
Jul 24, 2000
Messages
5,058
What I'd like to know is why some people call them "hot water heaters" and not just "water heaters". Isn't it sort of implied that a water heater makes water hot? :)
/Mike
 

Jay Heyl

Stunt Coordinator
Joined
Apr 19, 1999
Messages
142
I was just looking into getting one of the Bosch tankless heaters. Most of the positive points have already been mentioned. The biggest negative for me was the requirement for a 5" flue. A standard gas water heater has a 3" flue. If you don't already have a 5" vent pipe your cost could go up considerably. (This is what killed the deal for me. I live in a condo that has a 4" vent pipe. No way I could get that changed to 5".)

The other big negative is that rather than heating the water to a fairly constant temperature, the tankless heater provides a fixed temperature gain for a given flow rate. So, at 2GPM you might get a 90F temperature rise, at 4GPM you'd get maybe a 50F rise. Depending on where you live, the difference between winter and summer could make a big difference too. (In Southern California the cold water might be 55F in the winter and 75F in the summer. Northern areas would tend to be more constant because the water mains are buried deeper where the temperature stays about 55F all year.) Anyway, depending on the time of year and the amount of hot water being used at any given time, the temperature of the water coming out of the tap could vary by 50F or more. You might get 110F or you might get 165F.
 

Craig Robertson

Supporting Actor
Joined
May 12, 1999
Messages
982
there are now two of the larger models that use a 4" flue. the 125FX and the 240FX. they are using a powered vent to get more flow thru the smaller flue.

it also looks like they now modulate the gas flow/flame size to regulate a constant output water temp.
 

Jay Heyl

Stunt Coordinator
Joined
Apr 19, 1999
Messages
142
Thanks for the info on the 4" flue. Unfortunately, that model is listed at $899. With installation I'm sure I'd be looking at over $1100. The top-of-the-line 50 gallon model from Home Depot, with 12 year warranty, would be about half that (also installed). I really like the idea of having a serviceable unit that will probably last 25 years or more with a little care, and the thought of not having to worry about another water heater tank springing a leak is a big plus, but I'm not sure these add up to double the cost. Maybe Home Depot could get me the power vent model for less than $899.

BTW, where did you find the info modulating the gas to regulate the temperature of the heated water? I looked on the site you mentioned in your original post and couldn't find anything that addressed this.
 

DaveBB

Supporting Actor
Joined
May 24, 1999
Messages
788
I've talked to a couple of plummers and they were all againts them for home use. Tankless water heaters are best for a situation where you have a sink/bathroom FAR away from where a tank water heater can be placed. For example a garage or large warehouse.
 

Users who are viewing this thread

Top