August 24, 2021: My goal was a simple, cost-effective plumbing system that minimized both cold and hot water use. I looked at—but rejected—a number of newer products and innovative strategies that (for my situation) seemed too expensive or too complicated. I reasoned that my habits were conservative already, that water here isn’t scarce or expensive, and that solar—not a fossil fuel—was heating my hot water.
WATER CONSERVATION The average American uses 88 gallons of water per day. Having camped and lived “rustic” for many years, I was confident I could beat that by at least half. But now that I’ve lived in the house for one year, I’m abashed to report that I’m no better than the rest (my number: 80 gallons). Irrigation is the wild card–seasonally, regionally and by household.
Even when I don’t look at the months I was getting my yard established and starting my garden, my water use seems too high—even though I chose (mostly) EPA WaterSense labeled products.
Toilets are the main source of water use in most homes, accounting for nearly 30% of indoor consumption. Older toilets use as much as 6 gallons per flush (gpf). My WaterSense labeled single flush toilet uses 1.28 gpf. A better choice would be a “dual flush” toilet (the kind with 2 buttons or levers)—which could save me something like 3 gallons/day.
Showerheads are limited to 2.0 gallons per minute (gpm)—the Delta unit I chose is rated at 1.75 gpm and claims to save on hot water with its innovative “thermal dynamic” design. It features a dual-control valve that allows you to turn off the flow of water mid-shower and still maintain water temperature for extra water savings while soaping up.
The bath faucet I chose meets the limit of 1.5 gpm. Interestingly, WaterSense is silent on kitchen faucets, though Wisconsin sets a limit at 2.2 gpm. The commercial style one I chose is rated at 1.75 gpm. I know it’s weird, but I like to hand-wash dishes and didn’t install a dishwasher.
Clothes washing machines are also not addressed by WaterSense, but the average Energy Star labeled appliance uses 13 gallons per load. To save on up-front costs, I bought a decades-old washing machine from my local appliance shop after they convinced me that it was so sturdy and simple it would probably never need servicing—unlike today’s bells & whistles models. However it has no water-saving features whatsoever, and may be using 30 or 40 gallons per load. All I can do is select for load size, and run it on cold.
Heating water for washing is typically a home’s second largest energy user, after space heating and cooling. As much as 15% of heated water is lost in distribution. Waiting for a tap to get hot isn’t fun, and watching all that cold water run down the drain is a drag. Back to back bathrooms or a compact arrangement of “wet rooms” with short pipes is an obvious solution—noted but not followed in my design. The two bathrooms in my house are at opposite ends, but do align with the centrally located hot water heater for straight runs. For no good reason other than I forgot to tell the plumber before he nailed them in place, my hot water pipes are sans insulation. Here’s a good article explaining how to optimize your system: “Why Your Hot Water Takes So Long”.
HOT WATER HEATERS Water heaters can be powered by gas, electricity, or solar thermal energy. They can be either “on-demand” (tank-less) or “storage” (with a tank).
Installing solar thermal panels to heat domestic hot water was for many years considered the most cost-effective way to transition to renewable energy. Solar energy can supply a significant amount of the heat energy needed, but it’s highly dependent on climate, solar orientation, and location. In all but tropical climates, some backup source of fuel will be needed—usually requiring a second tank to boost the insufficient temperature of the solar heated water.
According to GBA’s “Solar Thermal is Really, Really Dead”, this redundant system no longer makes economic sense. That’s because the cost of PV (photovoltaic) systems has dropped significantly. Another reason is that operational glitches are much more common with thermal systems, and finding installers or repair technicians can be difficult.
Tank-style According to“All About Water Heaters” the majority of water heaters sold in this country are tank-type water heaters heated by natural gas, propane, or electric-resistance elements. They’re widely available and inexpensive. Natural gas is by far the cheapest fuel, but electric-resistance are cheaper to install and they avoid the problem of venting.
Heat Pumps The newest technology to replace the common electric-resistance or gas-powered tank-style hot water heater uses a heat pump that extracts heat energy from the space around it. They represent the best value over the long term, but initial costs are high. In “Heat-Pump Water Heaters Come of Age“, the author explains that while the efficiency of electric-resistance water heaters is 100% (all the electrical energy sent to a resistance element is converted into heat)—-the efficiency of air-source heat pumps can be as high as 250%.
Besides initial cost and long payback period, there are other disadvantages. Heat pumps are bulky, noisy, mechanically complicated, rob space heat from the house during the winter, and require a condensate drain. According to energy expert Marc Rosenbaum, monitoring shows that the efficiency specifications provided by manufacturers of heat-pump water heaters are probably exaggerated.
For those households who have taken all measures to reduce their consumption, a high-efficiency, high-tech, expensive hot water heater makes less sense—the savings are too small to justify. On the other hand, for those households (or commercial buildings) that use a lot of water, heat pumps can pay off. A caution though: when large volumes of water are drawn off at once, efficiency suffers.
The best location for a heat pump is in a basement or large utility room where temperature drops of 2-6 degrees are acceptable and noise won’t be a problem (sound level can be 60 decibels—louder than a refrigerator). A small room isn’t big enough and the heat pump will over-cool the room—losing efficiency (warmer rooms are better). The room should be at least 750-1000 cubic feet, be above 50 degrees, be able to accommodate a unit height of 63-82”, and have a condensate drain.
Tank-less In “Are Tankless Water Heaters a Waste of Money?” the author explains that while more efficient that traditional tank-style heaters, tank-less heaters are more expensive. The appliances are mechanically complicated (and come with more maintenance problems)—meaning a few service calls could wipe out any energy savings. In one study, researchers concluded the natural gas tank-less heaters would break before they saved enough energy to justify their high cost, especially in retrofits.
On the plus side tank-less units are compact and can provide “endless” hot water. For single households or for families who use a modest amount of hot water, they might make more sense than keeping 40 gallons of hot water ready for use around the clock. A good application is a remote sink or a weekend home.
“Storage vs Tankless Water Heaters” points out that the electrical current draw is huge—40 to 60 amps if two showers are being used at the same time—this takes special wiring and special circuit breakers—both are expensive.
The author of “Point of Use Electric Tankless Water Heaters” declares himself an evangelical of the technology. While realistic about the problems, he’s installed several systems that work well.
I chose a 30 gallon Rheem Marathon: these tank-style hot water heaters are in a category of their own. They use high quality electric-resistance elements in a super-insulated seamless polybutylene tank. According to the forum on GBA “How to Chose an Electric Water Heater” these units will last much, much longer than enameled steel tanks—they simply can’t rust out or leak. The manufacturer backs this up with a lifetime warranty.
Because the unit is lightweight and doesn’t contain an anode rod, installation is easy and maintenance virtually nil, according to this review. The heaters are insulated with 2.5” of foam (free of CFC and HCRC’s) to R-20 and will lose only 5 degrees in a 24 hour period (compared to a standard heater that can lose up to 30 degrees).
According to Green Building Advisor’s Martin Holladay, the Marathon might use 4 kwh/day vs. a heat pump that might use 1.5 kwh/day. That said, he thinks the Marathon plus a few extra PV panels is a better bet than the current generation of heat-pump water heaters.
My plumber, Gerry Thuli from Collins & Hying ably installed my unit. He was skeptical that a 30 gallon tank would be large enough to meet a household’s needs, but a recent family visit proved that 2 showers can be taken simultaneously, with hot water left over for a third person to do the breakfast dishes.