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,
Traditional hot water circulating systems form ajust luke warm, and it replaces the cold water
loop with the hot water piping that connects fromwith tepid. The system is not suitable for use with
the water heater outlet to the fixtures, and thena tankless water heater.
back to the water heater. A pump circulates theMetlund and Chilipepper make “demand”
hot water through the loop. These systemshot water systems. Demand hot water systems
provide nearly instant hot water at each fixture,are residential hot water circulating systems
but they are very expensive to operate. Theydesigned to work without a dedicated return, and
waste huge amounts of energy keeping hotare suitable for retrofit to existing homes. They
water in the pipe, and decrease the life of thealso use the cold water piping for a return line.
water heater. They are inappropriate for tanklessThe demand pumps, like the Laing pump, are
water heaters. Traditional circulating systems areplaced under a fixture where they connect the
made by Grundfos, Taco, Bell & Gusset, andhot and cold water lines. When the pump is
others.activated by the user pushing a button, it pumps
Laing makes a system suitable for retro-fitting towater out of the hot water pipe and into the cold
existing homes that don’t have a dedicatedwater pipe, and shuts off when the hot water
return line, called the Auto Circ. It is a small pumpreaches the pump. Demand system pumps are
that mounts under the sink, and pumps watermore powerful than the other types of systems
from the hot water pipe into the cold water pipe,to move the water quickly.
and when hot water reaches 95 degrees, theThe demand system has several advantages
pump shuts off. When the temperature drops toover the traditional system, and saves the same
85 degrees the pump turns back on and theamount of water. One large advantage is the
cycle repeats. The pump can handle severalreduction in energy usage. Since the demand
fixtures if the plumbing layout is correct. Thissystem only runs for a few seconds whenever
system uses a lot of energy since it keeps thesomeone demands hot water, it uses very little
plumbing full of above ambient temperatureenergy for pumping…typically less than $2.00 a
water, and the cold water line ends up with tepidyear. It stops running when hot water reaches
water not cold. The Laing autocirc is not suitablethe fixture, and so it doesn’t use any more
for use with a tankless water heater.hot water than what you would normally use
Grundfos makes a similar hot water circulatingwithout a circulating system. Another advantage is
system for retrofitting into homes that don’tthe much smaller installation cost. It’s easy
have a dedicated hot water return line. A pumpand 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
and does so because the pump at the waterenough water to activate the tankless heaters.
heater outlet is providing pressure. When hot