We need an adequate supply of hot water in our homes, establishments for lease and rental, and commercial buildings. Furthermore, they need to be energy efficient and fully functional to meet the needs of whoever is going to use them. Even though recirculation systems save water, they should not be allowed to run constantly otherwise they will increase energy consumption. Instead, we prefer to design hot water return systems that are controlled. Our engineers ensure you have a reliable supply of hot water from all fixtures all the time with our hot water return system designs.
We need an adequate supply of hot water in our homes, establishments for lease and rental, and commercial buildings. Furthermore, they need to be energy efficient and fully functional to meet the needs of whoever is going to use them.
In addition to the fact that there are various different types of storage type water heaters, there are different ways that engineers design hot water systems. Early types relied on natural circulation that did not rely on any sort of pump. It stands to reason that they were lower in energy costs and also very quiet. However, this type of system didn’t work well in large networks when major temperature drops were experienced.
Another option was to have a centralized system where water was heated and stored using a boiler or furnace.
Still common today, centralized systems may be direct or indirect and may rely on:
Indirect heating systems circulate via a heat exchanger.
Even though recirculation systems save water, they should not be allowed to run constantly otherwise they will increase energy consumption. Instead, we prefer to design hot water return systems that are controlled.
Well-designed water distribution systems can help to conserve energy. Simple factors that help include using shorter pipe lengths and smaller diameter pipe, as well as reducing flow but increasing flow rates, which will all help to reduce the length of time it takes for hot water to get to a fixture or appliance.
In addition to both environmental and cost benefits, our MEP engineers recommend these long-term solutions:
Hot water recirculation systems move water in a loop throughout the home, with pipes passing from the water heater (or heaters) close to plumbing fixtures and appliances. Then, when hot water is needed, it is released by a sensor or via a valve and takes just seconds to reach the required temperature. This can drastically reduce water waste and the time one has to wait for hot water.
There are different types of hot water recirculation systems including what may be described as dedicated and integrated loops, some of which are more energy efficient than others. Most are designed to connect water heaters and fixtures that are about 80 to 100 feet (25 to 30 m) apart.
In a dedicated loop, a circulation pump is mounted on a pipe connected to the water heater. The water is then constantly pumped past fixtures and appliances until a valve is opened at that point. Because it is kept continuously hot, hot water is literally available on demand at any time. However, when a recirculation system pumps continuously it can potentially use significantly more energy. Additionally, if hot water pipes and water heaters are not properly insulated they will lose heat as well, increasing energy costs.
In what amounts to an integrated loop that runs through the cold water line, the pump is installed beneath the fixture that is farthest from the water heater and relies on “demand controls” to sense when the water temperature needs to be increased. Commonly activated by a thermostat or timer, a sensor controls the pump when the temperature drops below and reaches a certain heat. This may be anything from 85 °F to 95 °F or a larger range from 77 °F to 104 °F. Because the hot water is re-circulated intermittently, it is a more energy efficient system, reducing water heating bills as well as electricity costs for pumping the water.
Water heating is responsible for a fifth of the energy used in most buildings with old boilers and dated distribution systems accounting for huge amounts of wasted energy.
An efficient hot water return system or recirculation system not only saves water and energy, but it also saves time, increases the convenience factor for consumers, and improves reliability. But, as mentioned above, integrated loops with demand controls are considerably more energy efficient than dedicated loops that circulate constantly.
According to the U.S. Department of Energy every year as much as 1.3 trillion gallons of water is wasted by households waiting for cold water to heat up. At the same time, as much as 1,600 kWh is wasted in the U.S. every year as a result of municipalities pumping water to homes that will simply drain out of the system while householders wait for the water to heat to the desired temperature. The water simply washes down the drain!
Demand hot water recirculating systems follow a very similar process to that followed when we turn on a hot water faucet. However, instead of allowing the water to run down the drain until it gets hot (or at least warm enough to be of use), it is returned to the water heater. When it reaches a pre-set temperature, a control switches the pump off and we have hot water to use. It’s easy to see how this saves both water and energy!
By keeping domestic hot water pipes in relatively short runs, we are able to save even more water in a well designed hot water return system.
