Home & Garden

About the House: Introducing the On-Demand Water Heater

By Matt Cantor
Wednesday April 01, 2009 - 09:42:00 PM

A Buddhist walks up to the hot dog vendor and says “make me one with everything.” (Long pause). The vendor takes his money but fails to return his change. The Buddhist says, “Hey buddy, where’s my change?!” to which the vendor replies, epicanthically, “Change must come from within!” 

Change is hard. I’m not much good at it myself, but in these carbon-footprint-concerned times, change is essential. The change I’m suggesting today is really very simple, but I suspect that it will not be well-received by many because it involves pushing a button. Although we are a button-pushing nation, we certainly aren’t used to pushing buttons before we use hot water, so this will be a new and frightening concept, and there will doubtless be screams of “Socialism!” and wailing and the gnashing of teeth. There are also many people in the world who do not push buttons, but they are not part of the problem, so we’ll leave them out of it. 

Water heating is an imperfect science. Water heaters, as we think of them today, aren’t much more than about 120 years old, and they tend to reside downstream of our showers and sinks by many yards of pipe. So, when we turn on the hot tap, the first thing that we generally find ourselves doing is flushing several gallons of cold water out of the piping before the hot water can arrive. This wastes both energy and water in a number of ways. First, it clearly wastes clean, treated water, an increasingly rare and expensive commodity. Global warming is simultaneously decreasing the Sierra snow pack and increasing evaporation, thus decreasing the amount of water that will be available to waste. California is expected to increase in population by over 30 percent in the next 20 years. If you think you’re waiting a long time to get into the bathroom now, just wait. 

But, as usual, I digress. The point is that we waste a great deal of water, as well as the energy to deliver it (which is about 19 percent of our state energy usage) every time we stand around waiting for the water to finally get hot. If you only waste 20 gallons of water a day, this will amount to 7,300 gallon a year at an expense of about $150 including the extra gas heating you waste in the process. Some claim as much as 17,000 gallons for a family of four. If this is true, you could save about $400 a year. 

As I’m quite sure you were expecting, I have a solution for you and it’s really quite simple and fairly inexpensive. 

Someone got all the way out of the box on this one. What if you didn’t mind a little warm water in your cold water pipes for a short while? If it didn’t matter, you could use the fact that you already have a “return loop” in the form of a cold pipe adjacent to all the hot lines throughout the house. All you have to do, to avoid wasting several gallons every time you want to heat water, is to run the hot water back through the adjacent cold line for a very short period (usually about 30 seconds) to fill up the hot line with fully hot water. No water is wasted at all, and in a very short while the cold pipes will cool off. It doesn’t really matter anyway unless you’re after a cold drink from the tap right around that time. The potential losses are tiny, but the gain is very large.  

Several companies are now making devices that do this. Actually, there have long been installations done by smarter plumbers or builders in which circulating pumps would run either all the time or on a timer, and this would do something similar. However, while these systems might save water and were intended for convenience more than anything else, they wasted a lot of energy by forcing the water heater to run far more often. The newer systems, such as Metlund’s D’MAND system, run only for a very short while once you ask the system to get ready for you. When you get ready to get into the shower (or do the dishes or the laundry) you push a button mounted near their device and it will run just long enough to heat up the pipes and then will shut itself down. (It has a little thermostat inside that triggers a relay that turns the pump off. Nice.) 

The whole item gets installed under the sink in the bathroom furthest from the water heater and connects to the hot and cold lines under the sink. An outlet is needed and may add to the expense of installation if one isn’t near enough. The whole device is about half the size of a loaf of bread and is nearly silent. A button, much like a doorbell, is mounted near the unit but there are remotes that can be put in other rooms where hot water gets used. If you don’t mind wasting a little energy, a motion sensor can be installed that will automatically turn on the device when you walk into the bathroom. Since you’re likely to be using some hot water when you enter the bathroom, this doesn’t seem so egregious a sin. 

On-demand water heaters are all the rage these days, and those of you who follow my birdcage liners know that I favor these—with some minor complaints. Our novel little pump-and-bypass is a good fit for any on-demand water heater as it can decrease the water loss and delay, which is a sore spot with some on-demand owners. I would now recommend that anyone buying an on-demand water heater look into some version of this bypass technology. BUT, these devices work just fine on all water heaters, including the old and sluggish. 

Grundfos also makes a similar system with the possible advantage of being able to place the pump in a location separate from the bypass valve. This might mean an easier installation if there’s not an outlet near the sink in the far bathroom. It’s worth a look. Plumbers will readily recognize the Danish pumpmaker’s name as it has produced an extremely high quality product for over 50 years. 

Whether you choose the Metlund, D’MAND, the Grundfos Comfort System, the Autocirc1 or any other system, this is a very smart choice for any of us and an easy way to decrease our water and energy usage right now. For the home handywoman, it’s also a manageable job. If you can install a faucet, you can probably do this job. The cost for the kits runs between $350-$600 depending on the type and and the supplier. 

The cities of Peoria and San Antonio are both offering rebates for the installation of these items and I cannot imagine what’s keeping California cities from doing the same. Maybe we have to speak up and demand that our legislators recognize this as a solution to promote and to offer economic incentives for. So now you have two things to do today. One is to head over to Moran Supply in Oakland, talk to my friend Ron and take a look at the Metlund models. The other is to write to our dear Loni (Assemblymember.hancock@assembly.ca.gov) about introducing some legislation to rebate the cost of recirculating systems.  

Change is never easy, but it can be good for you. I’m not sure you can say that same thing about the hot dog. 



Got a question about home repairs and inspections? Send them to Matt Cantor at mgcantor@pacbell.net.