It seems we struck a nerve with a couple of recent columns about on-demand water heaters. Also known as tankless water heaters, on-demand heaters deliver an almost-never-ending supply of hot water if properly sized and installed.

Our first column on the subject responded to a reader who wondered whether replacing a conventional water heater with a tankless model was a smart move. We said that conceptually that was a reasonable way to go. Heat only the water you use, rather than heating, storing and then reheating when needed. It makes perfect sense — we thought.

It seems we struck a nerve with a couple of recent columns about on-demand water heaters. Also known as tankless water heaters, on-demand heaters deliver an almost-never-ending supply of hot water if properly sized and installed.

Our first column on the subject responded to a reader who wondered whether replacing a conventional water heater with a tankless model was a smart move. We said that conceptually that was a reasonable way to go. Heat only the water you use, rather than heating, storing and then reheating when needed. It makes perfect sense — we thought.

Wrong!

The column produced a flurry of reader comments enumerating a plethora of problems they encountered in going tankless. Two weeks later we devoted the column to their comments under the rubric that "the devil’s in the details."

This generated a firestorm of e-mails in favor of tankless heaters.

One reader wrote:

"Your article was discouraging. In Europe, I’ve used many on-demand heaters, both gas and electricity fired, and have had no problems. The wait for hot water rarely exceeds 20 to 30 seconds. They rarely use a single heater for all the hot water needs, rather having a small heater in each bathroom and one for kitchen/laundry. Some systems in the United Kingdom have central hot water for laundry and kitchen and individual on-demand units for bathrooms. Why are these innovative water heaters such a problem here in the United States? And why do you exclude electric heaters in your discussion?"

We can think of one reason: cost. Multiple on-demand units replacing a single conventional water heater with their multiple gas lines/vents or electrical service will increase the cost exponentially and eliminate any energy savings that might be generated by the change in system.

We continue to believe that on-demand water heaters make sense. Whether they’re cost-effective is another matter. Installation often requires retrofitting by increasing the size of gas and water lines. Installation of a recirculation pump is often required to enhance the performance of the heater. …CONTINUED

Another reader did her homework and has a workable system in her large Orinda, Calif., home. She writes:

"I spoke to the manufacturer’s rep of my tankless water heater during our remodel four years ago when I was searching for energy-efficient solutions. Because of the long distances to various faucets in our four-story split-level, he recommended installation of a recirculating pump fitted with a timer. We did have to upgrade the gas line and also had PG&E (Pacific Gas & Electric utility company) upgrade the meter.

"The timer is set to go on during the hours we generally are using hot water. The recirculating pump provides instant hot water at any faucet when it’s on."

Another reader who is a contractor had similar advice:

"Adding a recirculating pump to a new copper supply line installed in a circuit of the plumbing fixtures gives the home dwellers instant hot water and increases the ready supply of hot water by the volume of the hot supply line. These little beauties can be set to a minimum temperature and/or time of day for convenience.

"On remodels and supply pipe upgrades, I insist on using this system and have nothing but pleased customers."

But we’ll let this reader have the last word:

"Caveat emptor is the order of the day. When the proper units are installed correctly by competent and honest plumbers, they perform very well.

"Remember, it might cost a bit more up front to redo a gas line, change out pipes, or get multiple bids, but it will certainly cost more to make changes after the fact if the system was improperly planned and installed. Beware those lowball bids. If it sounds too good to be true, it most likely isn’t true."

***

What’s your opinion? Leave your comments below or send a letter to the editor. To contact the writer, click the byline at the top of the story.

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