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Old 08-18-2014, 07:36 PM   #11
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i think your best bet is to do what matt30 stated by twining two 40 gal heaters together. Also keep in mind tankless heaters are not instant hot water they are endless. I think by many standards the property you have would be considered commercial. the other guys in this forum might be able to inform you. i know where i live a multi-dwelling is considered commercial. whoever you have put in your heater make sure they pull a permit and that it is done right. the other factor is do you have enough room for two heaters or one big one. you could do a 100 gal. light commercial heater. remember if you change from a 40 gal to a 75 or 100 gal you have to increase the vent size up past the roof. not sure where you live but you can get a 75 gallon residential heater from fergusons plumbing supply. any big supply shop will be able to get what you need.

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Old 08-19-2014, 05:11 PM   #12
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I definitely like the idea of twinning two 40 gallons it would be a lot cheaper, I don't have to haul off the one working 40G and there is room- but wouldn't the monthly power and gas bill to heat two 40G's be much higher than heating one 65 gallon heater? Twice as much, potentially?

As far as your question, no. In our state a rental building is considered commercial at 4 units. Anything under 4 is a residence. That includes a house divided into 3 efficiency units.

Last edited by jeffpas; 08-19-2014 at 05:15 PM.
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Old 08-19-2014, 09:31 PM   #13
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OK just to note after doing the math I'm back to one 65 gallon heater.
The new 40 gallon tank I'm looking at is rated at $277 a year average cost.
The 65 gallon tank is rated $320/yr.

Provided 65 gallons is enough, and I think it is..... as the two downstairs apartments are tiny as closets and have no baths just showers, 3 bathrooms total in the whole building. And let's not forget that the previous owner was renting all 3 apartments out on just the 40 gallon tank. For 20 years, apparently. Why they never complained, I don't know.

The 65 gallon tank would cost $207 more to buy at first...... but would save about $230 in heating costs every year over heating the two 40s.
( 2 x $277 ) - $320 = $230

That's assuming the old 40 gallon rates at $277 operating costs per year also, and its probably less efficient at that.

Last edited by jeffpas; 08-19-2014 at 09:56 PM.
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