Is anyone familiar with in-line or tankless water heaters for darkroom use? I have a 120v, 5 gal. tank water heater in my darkroom which can no longer keep up in the winter. Even though I only usually heat to 70° F, the incoming mountain water is about 50° and that is evidently enough to draw down the 5 gal on my 20 year old heater after about one hour or so. In Europe one sees tankless heaters that can be preset to a given temperature; probably they snake the water through a heated coil and are switched on by a microswitch that senses the flowing water. Even if one could not be set to run at 70°, I could mix with cold as usual.

Any advice would be appreciated. Thanks.

-- John Hennessy (northbay@directcon.net), January 09, 2001

Answers

Hi John, Go to MichaelHolligan.com. Mike is the host of a home buyers show on the Discovery channel. He did a feature several months ago on the SETS Tankless Water System. This tankless system is featured on the homepage of this web site. This unit should be perfect for you. They claim that even cold moutain water won't faze it. Hope this helps, Wil

-- Wil Hinds (Ytb@aol.com), January 09, 2001.

These things are often used on boats when plugged into shore power; perhaps you can find something from marine supply shops.

-- John Hicks (jbh@magicnet.net), January 10, 2001.

Tankless water heaters are very common and can be obtained at any well supplied plumbing supply store and even at many hardware and home-improvement stores. I've seen them in stock at Lowe's. They range from small point-of-use units that fit under the sink and are installed in between your water supply and faucet all the way up to natural gas or LP-fired whole house units that replace your house hot water heater. I have recently been considering a whole house unit myself, which Lowe's stocks and costs $500. Under-sink units usually start between $100-$200. They basically operate the way you mentioned by sensing water flow and turning themselves on. They are not usually easily adjustable and simply raise the water temp a given number of degrees at a given flow rate, I think about 25-30 degrees F at normal flow rates. This would be perfect for your situation.

BTW, I wish I had your problem. I live in the desert and my water temp gets down to 70 degrees F for a month or two in the winter. The rest of the time I have to bring it down with ice or other means. If I could find an in-line water chiller that would drop the temp even 5- 10 degrees for $100-$200 I would be thrilled. But I don't think such a product exists. Chillers are rather expensive.

-- J.L. Kennedy (bwphtogr4@yahoo.com), January 10, 2001.

If the hot water heater used to do the job, now doesn't, first try flushing it out. Hook a hose to the faucet near the bottom and let the water run out of it until it runs clear, and then some.

If that doesn't do it, and it is electric, clean or replace the heating element. You will have to drain the heater, and they remove the heating element (may be two of them, one near the top and one near the bottom). If may be scaled or dirty. Try cleaning with something like Lime Away or CLR. Or just replace it, they are pretty cheap at Home Depot.

-- Terry Carraway (TCarraway@compuserve.com), January 10, 2001.

When building my darkroom, I taked with a family friend, in the plumbing business, about demand heaters. His opinion was that they are exactly the WRONG solution for darkroom use. They are best at producing small volumes of very hot water, to make a cup of tea for example. The best solution for a darkroom, where you need a constant, low volume supply of hot (or even only warm) water, is a standard gas, or electric, hot water heater.

-- Ed Farmer (photography2k@hotmail.com), January 10, 2001.

Thanks for all the suggestions. Now that my kids flown the coop (please excuse the mixed barnyard metaphor)maybe my darkroom no longer needs its own hot water supply and I'll just plumb in the house hot water.

-- John Hennessy (northbay@directcon.net), January 10, 2001.

Ed,

There are two types of the demand heaters. The small hot water ones like your plumber was thinking of, and the ones for larger flow of less hot water.

The larger ones are used to supply the same requirements as a tank type heater. They are very common outside the US where there is not the room for a large tank, nor the desire to spend money (energy) to keep a large amount of water hot.

-- Terry Carraway (TCarraway@compuserve.com), January 11, 2001.

Terry,

Even these systems are optimally designed for the purpose discussed here.

One demand system is designed to provide very hot water in small volumes. This is done to conserve water. The water is quickly heated, right under the sink, to a high temperature. This aviods the need to run the water until hot water from the tank reaches your sink, thus saving you from wasting a gallon or so of water to get a quart of hot water. These ofter heat the water to temperatures of 140 degrees.

Other systems are designed for longer flow periods and produce lower temperature water (about 100 to 120 degrees). These are often used to conserve energy by heating water in locations where demand is high for short periods. This would include showers and dishwashers, or clothes washers. These items us a large amount of water for a period of a few minutes. The heaters used in these systems save energy since you need to keep the water heated 24/7 to provide for these units. The water is heated only as it is needed.

The best unit for darkroom is a 5 to 20 electric heater, dedicated to your darkroom, that can be turned off after your darkroom session.

-- Ed Farmer (photography2k@hotmail.com), January 11, 2001.

Ed,

But the second type will work fine for a darkroom. They will produce as little or as much hot water as you want, all at the same temp for as long as you run the water.

A tank type hot water heater starts with the water at a given temperature. As you draw off the water, cold water enters and mixes with the water in the tank, causing a temperature change. Also if the incoming water if very cold and the flow rate is too great, you will get to the point where the water gets colder and colder, until there is no hot water at all.

An on demand heater gives you the same output temp for same input temp and flow for as long as it runs.

Overall, given a choice I would put in an on demand heater.

-- Terry Carraway (TCarraway@compuserve.com), January 12, 2001.

Before you buy a demand heater check its lowest heat setting, check your needed flow, then calculate the flow from the hot side needed to maintain the desired 70 degrees. For print and film washing you may find the needed hot side flow quite small. Be sure the demand heater functions at this flow rate. njb

-- Nacio Brown (njb@sirius.com), January 14, 2001.

I don't want to drag this on forever: The smaller the heater, the more energy it uses to produce a given flow rate at a given temperature. This is why demand systems are not used for high volume systems. No matter how low he flow rate, a three hour darkroom session is a high volume use.

Take it or leave it.

-- Ed Farmer (photography2k@hotmail.com), January 15, 2001.

Ed,

How do you figure that? It takes the same amount of energy to heat the same amount of water the same number of degrees. The only difference is the loss due to inefficiences. And demand heaters are more efficient than tank type heaters.

This is NOT the undersink types made for hot water for tea or coffee, they are just small high temp tank type heaters.

The whole house demand heaters are very efficent.

-- Terry Carraway (TCarraway@compuserve.com), January 16, 2001.