## Hot water circulating and recirculating systems, sometimes called recirc pumps, are pumps
and systems that bring you instant hot water and conserve water in doing so.

Hot water circulating systems are hot water systems
that circulate hot water through the hot water piping so that obtaining
hot water is nearly instantaneous. They are often referred to as re-circ, recirc,
or recirculating pumps.

This area of the Chilipepper web site provides an explanation of how the various types of hot water circulating
systems work complete with illustrations of hot water circulating systems
and other basic plumbing layouts.

### Types of recirc systems include continuously
circulating, timer controlled, temperature controlled,
demand type, and combinations of all of these.

Hot water circulating systems generally provide convenience
and save water but at the same time can waste large amounts of energy and
cost the home owner a great deal of money.
As an example lets see how much energy is lost from
a typical recirculating system. For our example we will
calculate the amount of energy lost from a 3/4 inch copper pipe 50
feet long representing the piping through a home, and a 1/2 inch
copper pipe 50 feet long representing the return line back to
the heater.

Let the ambient temperature be 70 degrees F, a hot water
temperature of 140 degrees, a 75 watt circulating pump running full time,
and lets assume the piping is insulated with 1/2 thick
insulation. There are 8,760 hours in a year.
For the 3/4 inch pipe the heat lost from the pipe
is 12.4 Btu/ft-hr., and for the 1/2 inch pipe the loss is 9.9 Btu/ft.-hr.
Doing the math we find that the losses for this system total to 9,767,400
Btu/year. If the pipe is not insulated the losses come to
a whopping 37,492,800 Btu/year.
Figuring the energy required to run the pump gives
us 657kWhr/year.
Gas and electric rates vary widely, but assuming 50
cents a therm (100,000 Btu) and 10 cents/kWh, it would cost $114.53 per
year to operate. With the bare pipe
version it would cost $253.16 per year to operate.
Maximum efficiency is obtained when the plumbing is
designed for the circulating system, but in many cases a home
owner wishes to add the recirc system to a plumbing system
that already exists.
The following pages describe the various
circulating systems and pumps in detail, how they operate, and the pros and cons associated
with them.
Traditional Circulating Systems

Cold water return circulating pumps

Thermo-siphon circ systems

Metlund D'mand VS CP6000 demand systems
compared

Tankless Water Heater Information