Begin by eliminating as much waste as you can. First, figure out how much water (and water-heating energy) your household currently uses. Establishing this base load makes it easy to quantify how much you save by applying the advice in this chapter.
To establish a water use base load, look at your water bills, month by month and over a whole year. If you have landscaping that doesn’t get watered in winter, comparing your winter and summer water bills will give you a good idea of how much water you use for landscape irrigation (assuming that the rest of your water consumption remains fairly steady year-round).
To establish a water-heating energy use base load, subtract all non-water-heating energy uses from your total energy use. Begin by comparing your summer utility bills with your winter utility bills. If your furnace and your water heater are both gas fired, your summer utility bills will indicate your gas usage minus the energy used for winter heating. If your range and oven are also gas fired, you can read your gas meter; eat cold food, eat out, or use a hotplate for a day; then read the gas meter again to subtract cooking gas usage from your total.
If you have electric water heating, start with a year’s worth of utility bills. Then use a Kill A Watt meter to measure refrigerator electricity use over a week or two. Multiply this out to represent a year’s use and subtract the result from your total annual electricity use. If you have electronics like TVs that use a lot of power, use the Kill A Watt meter to measure their electricity use. In the same way, remove any other large loads from your total annual electricity use. The amount that remains is your water-heating energy use base load.
Time-to-Tap: What Are You Waiting For?
When you turn on the hot-water faucet, you have to wait for the hot water to arrive. What flows first through the pipe from the water heater to the tap (and then down the drain) is the cooled-down water that’s been sitting in the pipe—the water you already heated last time you turned on the hot water. How much water are you running down the drain? You can measure it by collecting it in a bucket while you wait. Let’s say it’s 2 cups. If so, you’re in pretty good shape; the distance between your water heater and the faucet is probably short. If you’re wasting more than 2 cups, there’s plenty of room for savings.
Let’s look more closely at that water sitting in your pipes. When you turn off the tap, all the water in the pipe between the water heater and the tap begins to cool. If your pipes are uninsulated and are at room temperature, that water can cool down pretty quickly. If the surrounding temperature is colder—if the pipes are in a basement or crawl space or under a concrete slab—the water cools down even faster. But if your pipes are insulated or are in a hot attic, the water cools more slowly.
You may be able to cut the amount of cool water that is wasted while you’re waiting for hot water by insulating any uninsulated distribution pipes. But how much you can save depends a lot on when hot water is used in your home. If you use hot water only for an hour or so in the morning and a couple of hours in the evening, insulating your distribution pipes probably won’t save you much. That’s because even with insulation, the hot water in your pipes will eventually cool down to match the surrounding temperature; insulation slows heat loss, but it doesn’t stop it. So water that was hot in the morning will be cool again by evening. On the other hand, not too much heat will be lost if the times when you use hot water are clustered together, even if the distribution pipes are not insulated. If your hot-water use is spaced throughout the day, your potential savings from insulation will be greater.
You might also be able to save energy by reconfiguring the routes from hot source to tap, or by installing a recirculation system, as described below, but these are both fairly expensive options.
Maintain Your Water Heater to Maximize Its Efficiency
If you have a gas- or oil-fired unit, also have the plumber check the air supply and venting.
Once your tank has a curved dip tube, you can clear out sediment every six months:
Once your plumber has demonstrated these tasks, you can continue to do maintenance yourself.
Now and then, just stop and look at the heater. Is rain coming down the vent pipe? Did the cat knock the vent pipe loose? If so, call your plumber.
Insulate the Storage Tank
If your tank-style water heater was purchased after the mid-1990s, it probably has tank insulation built in. In that case, it’s best not to add insulation (the benefit won’t be worth the cost).
But if your water heater is older than that, it might not have adequate insulation. If you place your hand on the tank and it feels warm, it needs more insulation. Insulating your water heater is an effective, inexpensive task that you can do yourself and that you won’t regret doing, especially if the tank is in unconditioned space, such as your garage, basement, or outdoors.
Add-on water heater tank insulation is cheap and readily available at home improvement and hardware stores. When you buy tank insulation, look for an R-value of 12 or greater.
Insulate the Pipes
A great water heater won’t save you much water or energy if hot water frequently gets cold in the pipes. As explained above, if you use hot water throughout the day, and often have to wait a long time for the water at a tap to get hot, insulating your pipes might be a good idea. It will be easiest to do this when you’re changing the plumbing, since pipes affixed to, or inside, walls and ceilings are harder to wrap with insulation.
Pipe insulation sheaths are made of foam or fiberglass. They usually come with a lengthwise slit, so you just snap them onto the pipe. Use ¾"-thick foam or 1”-thick fiberglass (½” in a tight space) as a minimum, and seal all joints carefully with acrylic tape.
Insulate all the hot-water pipes in the house and the first 5 feet of the cold-water inlet at the water heater. Hot water tends to float up into the cold-water inlet, cool off, and drop back into the tank; adding insulation or installing a heat trap reduces this effect.
Use Less Water
Using less hot water is the cheapest and easiest way to save on both water and energy. There are two ways to save hot water: by remodeling an inefficient hot-water system and by using hot water more efficiently. An inefficient system can be made more efficient by reducing the length of the piping and by sizing it for the available water pressure. Remodeling gives you an opportunity to do this, but it can be expensive.
However, it costs little or nothing to use water more efficiently. The most effective way to save water is by changing your habits. Understanding how the equipment works and using it efficiently can go a long way. Here are some easy, and free, ways to change the way you use water:
Save Water in the Landscape
If you haven’t been water aware, it will probably be easy for you to cut a lot of water waste in your yard. Growing regionally native plants, which are accustomed to the rainfall in your area, costs far less than keeping up a lawn. You can reduce evaporative water losses by
Recycle Your Water
Graywater is any wastewater that has been used in the home except water from toilets. Dish, shower, sink, and laundry water make up 50–80% of residential wastewater. This water may be reused for other purposes, especially landscape irrigation. It’s a waste to irrigate with great quantities of drinking water when plants thrive on used water containing small bits of compost. (Note: While we’ve used graywater for irrigation for generations, codes in most states do not allow water from dishwashers and kitchen sinks to be reused.)
Here are some of the benefits of using graywater:
Use biocompatible soap in any water intended for reuse, and don’t recycle diaper-washing water. Thanks to the growing popularity of graywater use, you can find plumbers experienced in installing systems that divert your shower water or laundry water into your garden. Some techniques, such as bucketing water from your kitchen or shower, won’t require a plumber. A laundry-to-landscape system can be installed by a do-it-yourselfer. But most water-recycling techniques will require professional help.