Water heater for darkroom...tank or tankless

Dave Swinnard said:

I will go with a tank unit, power is already there. but I'm afraid I'll have to go with a 20 gallon based on size constraints. (it's that or just cold water...)

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You probably don't need much more than 20 gallons since the hot water demands are so low. As you're using electrical power instead of gas I would DEFINITELY go with a conventional heater; the increased initial price of the electric heaters takes a LONG time to get paid back...especially when you're not using the unit all that much.

Sundowner said:

You probably don't need much more than 20 gallons since the hot water demands are so low. As you're using electrical power instead of gas I would DEFINITELY go with a conventional heater; the increased initial price of the electric heaters takes a LONG time to get paid back...especially when you're not using the unit all that much.

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In BC, we are blessed with relatively cheap electricity, but I would go with an electrically heated tank anyways, because it frees you from most venting concerns.

And Dave, don't forget to get a really well insulated tank - for those frigid Parksville winters .

(For the uninformed, Parksville has the highest average winter temperature in Canada - the retirees absolutely flock there!)

MattKing said:

In BC, we are blessed with relatively cheap electricity, but I would go with an electrically heated tank anyways, because it frees you from most venting concerns.

And Dave, don't forget to get a really well insulated tank - for those frigid Parksville winters .

(For the uninformed, Parksville has the highest average winter temperature in Canada - the retirees absolutely flock there!)

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Hey Matt!

Hydro prices on the Island are NOT relatively cheap compared to the mainland. Our first heating bill last fall (all electric) for a house half the size of the Coquitlam one was more than double the Coquitlam one. We had gas run in ($$) for a fireplace last February and our winter bills dropped significantly.

Retirees, yup. Only Qualicum Beach (10 minutes farther up the road) has an older per-capita population in Canada.

You might want to consider longevity when comparing tank to tankless - and not the numbers in the sales brochures, but some independent reports. If you intend to stay in that house for a while, it may pay to go with something that has a longer life.

Now for my personal bias:
- I'd go for a tank heater with a very high efficiency rating. If it's only for darkroom work, you can also set the heat low as you won't need it as hot as you would in the kitchen or bathroom.
- I don't trust the "instant" heaters - though I'm thinking whole-house, not something as specific as you are. I've read the data, and used a few in action, and was not particularly impressed.
- Personally, I'd run a natural gas line to the garage (if your house has it) and use a water tank.

On the other hand, a tank may not be great if it's not constantly in use. Setting for long periods may somehow affect the quality of the water; chlorine does dissipate with time (I'm thinking of something growing in the tank, though don't know how likely it would be).

Truzi said:

On the other hand, a tank may not be great if it's not constantly in use. Setting for long periods may somehow affect the quality of the water; chlorine does dissipate with time (I'm thinking of something growing in the tank, though don't know how likely it would be).

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You don't want legionella growing in your tank. The recommendations I have seen say the tank should be set to 140F/60C to kill legionella. Then use a tempering valve to reduce the temperature to the hot water line down to 120F/48C. Doing this will also let you stretch the amount of hot water you get from the small tank size you need to fit your darkroom.

msage said:

About 5 years ago I worked in a lab that had a gas tankless water heater and we had nothing but problems maintaining 70 degrees for B&W processing.

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Certainly a tankless task!

Controlling legionella is pretty simple; 0.5 ppm chlorine added to the water - which most municipalities in the US already do, although Canada may be different - or maintaining hot water temperatures that are 125° or above; either will not only prevent any active bacteria from multiplying, but will also kill off any new entrants into the system in relatively short order. This is one of the reasons that we set any heater we install to 125°; the other is that 140° is hot enough to cause severe discomfort. Personally, I'd put in the conventional tank-style heater, set it at whatever temperature I wanted that was 125° or above, and invest the significant amount of money that I'd saved from NOT buying a tankless heater into a nice tempering faucet.

Also: periodic maintenance on a water heater will greatly extend its life. Flush the tank once or twice a year, change the elements as needed and check the anode, and you can get a LOT of life out of a modestly-priced unit.

Well the the trigger's been pulled and a 67 litre (~17.7 US Gal, or 14.7 Imp Gal.) tank was ordered - (or back-ordered actually) electric as there is already service to the space in question. Gas was run in last winter so we could heat at least part of the house with a gas fireplace, but was ruled out for the back garage.

We're chlorinated here so I'll go with the 125F setting. The money saved not going tankless has already been spent if you talk to SWMBO. (drainage and water so I would need a water heater...)

Got the sleepers down (level floor, yay), the subfloor down and about to start the partition wall...

So much closer to having a darkroom again after two years of NOT.

Tanks to all of you!

Good to hear of the progress, Dave!

I have a 40 gal gas-fired water heater in my garage...where the darkroom (or dimroom as some alt. process say) will be going in soon (hopefully!) If the water heater fails on me, I would consider building it a little insulated shed attached to the outside wall of the garage for the new one...get a little more floor space (also have the washer and drier in the garage) and no worries about leaks from the water heater. I use acetone in carbon printing, so not having a flame source in my dimroom would be nice. I could use straight grain alcohol (Everclear) instead of acetone...a little for the tissue, a little for me...But I think I'll keep to the acetone and just use a different room for it, or install sort of an exhaust hood that exhausts outside.

Vaughn