Hello,

I have been reviewing water heater options extensively with no good conclusion and need advices (or confirmation). Note that I am cheap and do not want to spend more than $800 total but I also want to reduce my impact on the environment (more a feel good thing than a monetary thing really).

My current (very rusted) 50Gal 50K 0.54 EF BTU gas water heater sits in a closet in the basement in the center of the house (far from any wall) and shares a Type B vent with the 100K BTU 80% AFUE inducted draft furnace. (Speaking of which, according to everything I have read, my Type B vent should have been corroded by my furnace exhaust's condensation already)

I am disappointed by the options I can find. I read about the $300 tax thing for high efficiency models (>0.80) so looked into it.

Bosch Aquastar tankless uses Type B vent but cannot share with induced furnace and anyway 100K BTU + 118K BTU may be too much for my 6" OD Type B vent. (I may need additional fresh air intake too to avoid getting negative pressure in the basement).

Everything else seems to use other venting methods.
The other tankless gas water heater I found make use of the "gold plated/platinum plated/diamond encrusted price" stainless steel Cat III pipes. This costs a lot. The Rinnai use a PVC pipe (much better from an installation point of view).

Besides, I do not see where I could route this venting unless I put the water heater on a wall. That would be in the finished basement (play room) or in the crawl space.

I have a crawl space under half the house (split level) but it's 42" high and only sticks about 6" above ground so a vent there would end up under snow level (in the Chicago area). I suppose that I could put an elbow there and go up straight along the house and hide it into a fake chimney maybe. Wouldn't the condensation trap at the bottom freeze in winter? Would it be worthwhile to install it outside in my kind of weather since I believe they use about 100W to protect from freezing in winter.

Is there a tankless water heater that would fit there? I have not found any so far as they all are small but have high clearance requirements (like 12" above and under the heater).

I also looked at the tank gas water heater but frankly most of them (99%?) seem stuck in the stone age and seem to have the same specs as my 10 years old one!! (0.58 EF when my old one was 0.54 EF?? Who are they kidding? Still using pilot lights?? ) The slightly more efficient (read R20 insulation instead of the lowly R7) are impossible to find and they don't want you to add insulation because "you don't need it"...

I could only find a few models that actually improved (a little) with things like power vent into PVC pipes and electronic ignition but they are a lot less efficient and more expensive than the Rinaai tankless one.

Maybe I will just go with the absolute cheapest tank one, add insulation blanket and insulate the hot water pipes and hope that the manufacturers will have got out of their turpor by the time I need to change this one.


I am probably dreaming with my requirements. I would appreciate any advice.

Note that I found labman's question from 2004 (https://www.askmehelpdesk.com/plumbing/gas-water-heater-crawl-space-4345.html) but am not sure that electric would work for me so I will look into it some more (additionally, the electricity company just hiked prices more than 20% ). I have found some companies claiming that electric is overall cheaper than gas while other companies claim the opposite... confusion abound...

''Maybe I will just go with the absolute cheapest tank one, add insulation blanket and insulate the hot water pipes and hope that the manufacturers will have got out of their turpor by the time I need to change this one.''

That is about what I did last summer. I did put the new tank further toward the back of the garage reducing the distance to the point of use and rerouted some of the pipes reducing the wait for hot water. You want to look at where you use the water most often and have whatever water heater close to it. The instant hot water from a tankless heater is instant only at the outlet. You have the same wait for it to run through the pipe. When it comes to a small footprint, the less cooled off water you run down the drain, the better for the environment.

In the ongoing debate here on tankless water heaters, I have seen claims of installing a
Rinnai in a crawl space. They are only available professionally installed, and you won't touch one for $800. If you go with one, you get bragging rights at the senior citizens center about following Paul Harvey's advice. I don't hang out there.

Pilot lights still make sense on hot water tanks. The heat from the pilot light helps make up for the heat the tank loses. It can't be that much. In the summer we only use 10-12 cuft a month for the pilot light, heating the hot water, and the gas dryer. Compare your last summer's gas bill to the figures the tankless vendors give for gas used by hot water tanks.

I am glad somebody else is actually looking past the marketing at the real numbers.

I have just looked at the electric ones and am puzzled by the state of affairs.

I use 240 Therms per year on average to heat my water (deriving from August gas usage), which translates into 240*29=6960 KW. At 54% efficiency (according to the ratings), only about 3750 KW make it into hot water from my gas heater, the rest being building heat and heat out the flue.
This is interesting because it matches the average usage for a 50Gal electric heater according to the various tables everywhere.
However, I pay less than $1/therm and about $0.11/KWh today, even wasteful gas water heating is still cheaper than electric. (less than $240/year compared $412/year)

Maybe I just need an efficient gas generator to power an electric water heater. That one could sit outside with no water line to freeze. I looked at heat pump, but air based ones are really only good for moderate climates and ground ones cost a lot to install (what with drilling deep holes... )

In the meantime, I suppose that I indeed have to stick with a good old gas tank heater with extra insulation everywhere. (Maybe a drain/gray water heat recovery system could be added somehow.)