Jim Rooney On The Level

Q. Our water heater isn’t old and doesn’t need replacement yet but we are interested in doing anything that might make it more economical to have. There is just the two of us living here. I’ve read about putting a timer on it so it’s not using electricity all the time. It seems to be a cost effective device. Please explain the pros and cons of a water heater timer.

A. Basically a timer is a switch that you control to turn the water heater on or off at whatever time of day you desire. There are more pros than cons about their use. Traditional electric water heaters are little more than big metal tanks that have heating elements in them that are controlled by integral thermostats now factory set at 120ºF. They are adjustable and can be set higher or lower but the 120ºF setting is an anti-scalding setting for basic user safety.

Where traditional tank water heater inefficiency enters in-- compared to on-demand or “tankless” water heaters or the new hybrid water heaters that are part heat pump, part traditional type-- is the energy they lose in their stand-by mode. They are designed to hold water at the set temperature round the clock waiting for someone to use it. If you think about it, most folks really don’t use that much hot water over a day’s time and when they bathe they actually mix the water coming from the hot tap with cold to bring it down to a more comfortable temperature. Modern showers use water at 2.5 gallons per minute. Doing the math for an average shower length might yield a use rate of less than half of the water heater’s capacity. You are rightly looking at that tank staying hot all day and all night waiting for about fifteen minutes use. It’s a big thermos bottle slowly sucking electricity to keep hot. Shutting it off for a while during the day or night via a timer makes sense.

When I am totally on my own in the house I’ll flip the breaker to the water heater off and keep using hot water at my regular rate waiting to sense the difference. It takes a couple of days before I’m forced to turn it back on. You can save an additional 5%–12% of energy by installing a timer that turns the water heater off at night when you don't use hot water and/or during electricity peak demand times. If you’re handy you can install the timer yourself. If not, call an electrician. They cost in the $60. range but they can pay for themselves in about a year.

Some folks additionally wrap their water heaters with an insulation blanket but I have never seen a payback period analysis that I trust on them but it certainly can’t hurt. Any penetration of the water heater’s own insulation envelope leaks heat and heat is energy and it costs. Those penetrations include where the heating elements enter the tank, where the inlet and outflow pipes and the temperature pressure relief valve are piped and the drain-cock at the bottom.

Another item now in use with newer water heaters is a thing called a heat trap and they are installed at both inlet and outflow pipes. They prevent heat from convecting up those pipes as the heater sits waiting for use. They can save you around $15–$30 annually on your water heating bill. Heat traps—valves or loops of pipe—allow water to flow into the water heater tank but prevent unwanted hot-water flow out of the tank. The valves have balls inside that either float or sink into a seat, which stops convection. These specially designed valves come in pairs. The valves are designed differently for use in either the hot or cold water line. A pair of heat traps costs only around $45. However, unless you can solder a pipe joint, heat traps require professional installation by a plumber. Heat traps are most cost effective if they're installed at the same time as the water heater is installed and not retrofitted.

After you’ve done all you can to conserve what heat is in the water heater consider the temperature setting. I know residential water heaters arrive preset at 120º but there is a lot of microbial life that can survive in that temperature water. Legionella, the bug that causes Legionnaire's Disease, can live in water up to 131.9ºF and so can a bacteria called SRB, or sulfur reducing bacteria. That’s the one that gives us that rotten egg smell, especially on well water. If you are concerned about either of those and don’t have small children around then turn it up to 140º. It’ll heat up to that level and cool somewhat while the timer has it off but a cycle of that degree of heating should keep the inside of the tank sanitary. Another plan for keeping water sanitary is installing a UVC sanitizing light on the water supply as it comes into the house. That’s about $400 but will kill 99.9% of any bacteria that passes it.

Keep the mail coming. If you've got a question, tip, or comment let me know. Write "On The Level," c/o The Capital, P.O. Box 3407, Annapolis, MD 21403 or e-mail me at jimrooney@jimrooneyonthelevel.com or inspektor@aol.com.