Tankless Gas Hot Water Heaters??

The water in your area ranges from moderate to medium hardness. This mean that the hard miinerals coat the heat exchangers and cause failure sooner than in soft water areas.

Constituent Range MCL
Calcium (ppm) 32 – 49
Not Regulated
Chloride (ppm) 14 – 50 250
Magnesium (ppm) 2 – 9 Not Regulated
Sodium (ppm) 12 – 35 Not Regulated
pH (units) 7.98 – 8.75 6.5-8.5
Bicarbonate (ppm) 79 – 148 Not Regulated
Carbonate (ppm) 0 Not Regulated
Total Hardness as CaCO3 (ppm) 89-156 Not Regulated
Total Alkalinity as CaCO3 (ppm) 65 – 121 Not Regulated
Phenol Akalinity as CaCO3 (ppm) 0 Not Regulated
Total Dissolved Solids (ppm) 137 – 255 500
Conductivity (mmhos/cm) 264 – 515 Not Regulated

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Water Hardness Guide
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Milligrams per Liter Grains per Gallon
or Parts per Million
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Soft 0 to 60 mg/L 0 to 3 1/2 gpg
Moderate 61 to 120 3 1/2 to 7
Hard 121 to 180 7 to 10 1/2
Very Hard over 180 over 10 1/2
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Source: American Society of Agricultural Engineering
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Tankless, or instantaneous water heaters, have small tubes that collect hardness to clog the exchanger. This is not a problem for Europe, where the Bosch unit is used extensively, because it is common practice for the factory technicians to come to the home to disassemble and clean the units. It is acceptable there to replace the exchanger or entire unit once in five years.

This is not a common practice in the US. Such units work well in flows greater than 1/2 a gallon per minute. When flows are low, as in a draw for a pot of water, the firing rate is less stable.

“Demand Water Heaters
It is possible to completely eliminate standby heat losses from the tank and reduce energy consumption 20% to 30% with demand (or instantaneous) water heaters, which do not have storage tanks. Cold water travels through a pipe into the unit, and either a gas burner or an electric element heats the water only when needed. With these systems, you never run out of hot water. But there is one potential drawback with demand water heaters — limited flow rate.

Typically, demand heaters provide hot water at a rate of 2 to 4 gallons (7.6 to 15.2 liters) per minute. This flow rate might suffice if your household does not use hot water at more than one location at the same time (e.g., showering and doing laundry simultaneously). To meet hot water demand when multiple faucets are being used, demand heaters can be installed in parallel sequence. Although gas-fired demand heaters tend to have higher flow rates than electric ones, they can waste energy even when no water is being heated if their pilot lights stay on. However, the amount of energy consumed by a pilot light is quite small.”
http://www.eren.doe.gov/erec/factsheets/watheath.html

One good reason to install an instant water heater is that one line would suffice for a bathroom supply, which could be branched for hot and water supply. In this case, the hot and cold water pipes are already in place.

For small flows from the sinks, an electric instant water heater at the point-of-use would suffice.

Harold, Thanks so much for taking the time to give me all this information. While my hot water demands are not extensive, my major concern was maintenance costs and energy savings. If I understand you correctly, maintenance in this area may be a problem…which I do not need; and the savings on gas might not be that significant. If this is not correct, please advise.

My options for regular hot water heaters are to replace my existing 40-gallon unit in the hall closet with a newer model, or it was suggested to put a “low boy” in my attic. I have just installed a new Lennox 4ton AC/Heating unit in my attic and was wary of relocating a hot water heater in the same area…..any thoughts on this topic????

As I mentioned, I am in a wheelchair and responsible for my home up keep (will soon be living alone) and want to keep everything as simple and cost efficient as possible. As I remodel my hall bath (updating to an accessible design, fixing leaks, and treating for termites, etc), I want to make informed decisions and spend my limited money wisely. As I continue to get various opinions and recommendations from contractors, I would greatly appreciate any advise/suggestions from someone that is not bidding on this project.

Replacing the water heater in the hall closet requires little in pipe changes and retains the security of having a pressure vessel full of water near the bottom of the house instead of overhead. Placing the water heater in the closet on a combination raising platform and leak pan adds some more security.
http://www.whelevator.com/Technical_Information/technical_information.html

Harold,
Thanks for your input. I appreciate the time you have taken to answer my questions.

Opps, almost forgot….is there one brand/type of gas hot water heater that is the best. My main concern is maintenance and energy savings here in N. Texas. I will be purchasing a new one within the next two weeks. Thanks