Hot Water Circulating Systems - Cold Water Return for Instant Hot Water

For water heaters that don't have hot water circulating systems there are alternatives to the expensive and difficult process of adding a return loop, hot water circulating pump, and the associated equipment required for a traditional hot water re-circulating system.

Low cost retro-fit instant hot water is inexpensive and easy to install

The cost of such a retrofit could easily run into the thousands of dollars. Tearing out sheet rock and running pipe under crawl spaces and in attics is expensive.

The alternative to such a system is what's known as a cold water return type system. One such system is the Chilipepper appliance.

Another problem with the traditional water heaters hot water circulating system is that unless it is planned before the house is built, the piping system is usually branched and not series plumbed, the proper method for circulating systems.

A traditional hot water circulating system is a big energy waster.  The continuously running pump uses quite a bit of energy over time, but the big energy waster is the staggering amount of heat lost from the hot water piping and return line.

Because the re-circulating pump normally only runs for a few seconds each time heated water is desired, the pumping energy is very small, typically less than a couple of dollars a year. And since it doesn't constantly keep hot water in the lines it doesn't use any more energy than a non-circulating system.

The add on type systems use the cold line as the return line for the circulation loop. In these systems the pump is located under the fixture where fast hot water is desired, and connects from the hot pipe to the cold pipe. 

When used with a branched system sometimes one pump can serve several fixtures and sometimes more than one pump would be required to serve multiple fixtures.

diagram of a hot water recirculating system for instant hot water

on-demand type circulating system

The on-demand type of cold return, circulating system incorporates a button or other device to turn on the pump when hot water is desired at a fixture.

The pump in some systems (such as the Chilipepper) is strong enough to pump at a much faster rate than it normally flows from the tap, getting the hot water to the fixtures more rapidly than running the faucet.

As with traditional circulating systems, nothing is wastefully run down the drain.

Temperature control type system

Some cold water return type circulating systems use a temperature control to turn the pump on and off. These systems use temperature set points that are low so that the cold line does not end up full of hot water, just luke warm.

Both the on-demand type circulating systems and the temperature control type systems can be used with timers.

Instant hot water systems such as the Chilipepper and the Metund d'mand ® system use the cold water line as a return and save you time, water, energy, and money!