Hot Flash!. Instant Hot Water Systems Explained and 5 Brands Compared

Residential hot water circulating systems providewater reaches the valve, the valve closes. This
the user with fast hot water providing akeeps hot water near all the fixtures in the home
convenience for the user, and saving the waterwith just one pump. However, like the Laing
that would have been run down the drain.Autocirc, it doesn't really deliver hot water, just
Traditional hot water circulating systems form aluke warm, and it replaces the cold water with
loop with the hot water piping that connects fromtepid. The system is not suitable for use with a
the water heater outlet to the fixtures, and thentankless water heater.
back to the water heater. A pump circulates theMetlund and Chilipepper make "demand" hot water
hot water through the loop. These systemssystems. Demand hot water systems are
provide nearly instant hot water at each fixture,residential hot water circulating systems designed
but they are very expensive to operate. Theyto work without a dedicated return, and are
waste huge amounts of energy keeping hotsuitable for retrofit to existing homes. They also
water in the pipe, and decrease the life of theuse the cold water piping for a return line. The
water heater. They are inappropriate for tanklessdemand pumps, like the Laing pump, are placed
water heaters. Traditional circulating systems areunder a fixture where they connect the hot and
made by Grundfos, Taco, Bell & Gusset, andcold water lines. When the pump is activated by
others.the user pushing a button, it pumps water out of
Laing makes a system suitable for retro-fitting tothe hot water pipe and into the cold water pipe,
existing homes that don't have a dedicated returnand shuts off when the hot water reaches the
line, called the Auto Circ. It is a small pump thatpump. Demand system pumps are more powerful
mounts under the sink, and pumps water fromthan the other types of systems to move the
the hot water pipe into the cold water pipe, andwater quickly.
when hot water reaches 95 degrees, the pumpThe demand system has several advantages
shuts off. When the temperature drops to 85over the traditional system, and saves the same
degrees the pump turns back on and the cycleamount of water. One large advantage is the
repeats. The pump can handle several fixtures ifreduction in energy usage. Since the demand
the plumbing layout is correct. This system uses asystem only runs for a few seconds whenever
lot of energy since it keeps the plumbing full ofsomeone demands hot water, it uses very little
above ambient temperature water, and the coldenergy for pumping…typically less than
water line ends up with tepid water not cold. The$2.00 a year. It stops running when hot water
Laing autocirc is not suitable for use with areaches the fixture, and so it doesn't use any
tankless water heater.more hot water than what you would normally
Grundfos makes a similar hot water circulatinguse without a circulating system. Another
system for retrofitting into homes that don'tadvantage is the much smaller installation cost. It's
have a dedicated hot water return line. A pumpeasy and economical to retrofit to any house.
connects to the outlet of the water heater, and aDemand systems have more powerful pumps
thermally controlled valve is placed at each fixturethan the other systems and so the Chilipepper
in the home. The valves are connected betweenpump and at least one of the larger Metlund
the hot and cold water lines. When each valve ispumps will work with tankless water heaters.
cold water can flow from the hot line to the cold,Most of the circulating pumps won't pump enough
and does so because the pump at the waterwater to activate the tankless heaters.
heater outlet is providing pressure. When hot