Hot Water Demand Pumps Save Water AND Energy

Posted on: February 5, 2014
By: Alan O'Neill
Posted in: Plumbing

Clean water is a valuable resource and it should not be wasted – especially waiting for the hot water to reach your tap. With a rapidly expanding population and droughts occurring frequently and lasting longer, saving water is becoming increasingly important. Homes with long pipes running from the water heater to the faucets can have a long wait for hot water. The hot water in the pipes cools when it is not in use. The heat loss is significant even if the pipes are insulated. So all this cool water runs through the pipe before the hot water can reach your faucet. This wastes water and energy, not to mention the inconvenience. In an average household, the water wasted can add up to thousands of gallons per year. 

The remedy: a water recirculation system. These systems overcome the problem by keeping hot water in the supply pipe. They slowly pump hot water through your hot water pipes and send it back to the heater through a dedicated line or through a special manifold on the cold water line. Several models are available and some may save thousands of gallons a year while using very little energy.

Most of these systems use a pump to circulate water. Several types are available depending on your needs. The circulation pump for a system with a dedicated loop is mounted on a pipe connected to the water heater tank. The hot water pipe is installed in a loop throughout the home, passing near each plumbing fixture. At each fixture, a short pipe connects the loop to the hot water valve. Because hot water is constantly circulating through the hot water loop, any time a valve is opened, it takes only a fraction of a second for hot water to reach the valve.

Systems with an integrated loop typically are installed to retrofit a home. The pump is usually installed at the eater heater and the special manifold under the plumbing fixture farthest from the water heater. In this system, hot water is returned to the water heater via the cold water pipes. This raises the temperature of the cold water slightly, but it returns to the usual cold temperature quickly.

Some models run 24/7, constantly circulating water through the pipes. Others can set on a timer so that the pump is only running to prepare for peak demand times. For example, first thing in the morning the water in the pipes is usually at it’s coolest. You can set the timer to turn on at the same time your alarm clock wakes you up. The hot water will be ready and waiting.

Some models have a thermostat, which keeps the hot water at a certain temperature. Several manufacturers are now offering warm water recirculating pumps. These systems uses low flow hot water circulating pumps and in some cases sensors are placed under the sink at the fixture furthest from the heater. The sensor detects the water temperature in the pipe and will turn the pump on and off to maintain a lower temperature (between 85 and 90 degrees F) rather than hot water, which is typically over 98 – 104 degrees F. Some models offer the ability to adjust the temperature. 

The most energy efficient type of recirculating system is an “on demand” system. A demand-controlled circulation system (one that operates on a pump activated by a switch or motion detector) uses the least amount of energy and saves the most water. When you push the request button (or it’s activated by a motion detector) the pump comes on and sends the heated water to your fixture and returning the cool water back to the heater through the cold-water piping. The pump shuts off when it detects the arrival of hot water. The pump only operates when you want hot water without wasting the cold water. Generally, these types of “on demand” units can take between 1-2 minutes before you feel the hotter water at the fixture.

The energy used to run a typical pump is minimal. Most systems use a few dollars per year in electricity to operate. In addition to saving energy and water, hot water recirculation may improve the efficiency and effectiveness of household appliances (like washing machines and dishwashers) by having hot water available instantly.

There are benefits for each system. Your certified plumber can explain the differences between systems and will help you determine which system is best for your home. They may have discounts or rebates from the manufacturers. Your certified plumber may have additional suggestions and may have specials on equipment or other services. They may also have service plans, like The Abacus Club, that can help save you money on service calls and provide annual plumbing tune-ups. Abacus Plumbing & Air Conditioning just recently began offering a maintenance agreement for water treatment, which includes quarterly maintenance visits. 

Abacus Plumbing & Air Conditioning specializes in hot water solutions for residential customers in Houston, Texas. To learn more about hot water recirculating pumps, visit

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