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Circulating Hot Water Can Save You Money


QUESTION: We live in a drought area, and I'm concerned about the amount of water wasted while running the tap to get hot water to my bathroom. My water heater is at one end of my home and my bathroom is at the other. In order to get hot water through the faucets, at least 80 feet of cold water has to come out of the hot water line. Is it possible to continue the hot water line past the bathroom and then return it into the water heater? Will this save a lot of water?

ANSWER: The hot water system that you have, like those in most residential systems, is a non-circulating type. It is generally installed because it costs less for labor and materials than a circulating hot water system. Even though the non-circulating system is very common, it does have the disadvantage you describe.

You can convert your system to a circulating hot water system by installing a return loop on the distribution line that runs from the last faucet to the hot water heater. If the elevation difference between the hot water heater and the faucets is greater than 5 feet, then the hot water circulation can usually be achieved by gravity, the so-called thermo-siphon system. This works because hot water rises, forcing the cooler water down.

If there is a long horizontal run in the pipes or if there is less than a 5-foot height difference between the boiler and the faucet, the thermo-siphon system won't work, and you'll need a pump to circulate the hot water.

This system, often used in hospitals where instant hot water is required, has the advantage of making it available at all fixtures as soon as you turn on the tap. Continuous circulation between the hot water storage tank and the faucet does the job.

A circulating system will also save some water. Assuming you have a three-quarter-inch diameter water pipe between the hot water heater and the tap, the 80-foot pipe will hold about 1.8 gallons of water. This would be wasted while waiting for the hot water to come through.

However, a circulating system can be energy-inefficient because you have to heat the water that then cools down in the pipe when you do not use it. Insulating the pipes very thoroughly can help minimize this heat loss.

Refrigerator Thumps, but It Won't Explode Q: We have a Hotpoint refrigerator with a top freezer. Whenever the compressor stops, we hear a sharp thudding noise. This noise first appeared about three months ago as a quiet thud and has gradually gotten louder. Now the refrigerator has started to rattle. We're afraid it might explode one of these days. Will it? And what should we do to quiet it down?

A: There's no danger that your refrigerator might explode, but your thudding and rattling noises sound as if one of the internal suspension springs that mount the compressor may have broken. What you are hearing is the motor and pump assembly on its sub-frame hitting against the side of the compressor case that surrounds the entire compressor assembly. The only real cure is to have the compressor replaced.


To submit questions, write to Popular Mechanics, Reader Service Bureau, 224 W. 57th St., New York, NY 10019. The most interesting questions will be answered in future columns.

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