Slowly over the years a lot of things have changed, and a lot have not. For instance, gone are the days when opening your faucet wide open produced flows of 10 gallons per minute. Over time water has gotten much more valuable, and measures have already been put in spot to preserve water. These days all fixtures have flow restrictors and you just can’t get a 10 gallon per minute flow rate. The shower has pretty much been reduced to 2 gallons per minute and the toilet sink to about ¾ gallon per minute.
Years ago it was not unusual in high-priced homes to uncover hot water circulating systems that provided instantaneous hot water to the home owner at any fixture in the house. The plumber would run the hot water piping in a loop in the water heater exit to a fixture and from that fixture to the next and so on until he reached the last fixture. From the last fixture a conduit would run back to the inlet of the water heater where a pump and check valve were located.
The pipe from the last fixture back to the water heater is called a dedicated return line. A check valve located between the water heater inlet and the return line kept water from being drawn back through the return line when a fixture was in use. There would be a pump located at the water heater inlet, that would circulate the hot water keeping hot water in the piping each of the time at the water heater exit or at the return line. When a hot water tap was turned on there that way, would be instantaneous hot water.
Instant water is wonderful, but it truly is not cheap. By keeping the hot water piping high in hot water all the time a great deal of heat energy is being lost from the piping, even when fully insulated since there is so much surface area on a piping system. With the full time not only cover the heat energy being lost in the plumbing, but also you cover the energy to run constantly to the pump, and your water heater doesn’t last as long. It’s possible for you to put the pump on a clock timer and shut off the system but that can be rather an annoyance and the system will waste enormous amounts of energy.
A nice side benefit of immediate hot water is the conservation of water. You do not run thousands of gallons per year of water down the drain waiting to arrive.
One of the issues with hot water circulating systems is that they don’t work with tankless water heaters which are becoming very popular. The issue is that tankless water heaters are turned on when water flows through them. Since the circulating system continuously circulates the hot water, the water heater would be on all of the time. That simply wouldn’t work out very well. Since tankless water heaters take only a little longer than storage heaters to produce your hot water it is unlucky.
Yet, considering the cost of both water and energy these days there should be a way of saving both. What’s promising is that you can find systems that can do both. These systems are known as “demand” hot water systems since the user must require hot water to get it. How the user generally requires hot water is by pressing on a button near the fixture.
Most demand systems are marketed toward present dwellings that don’t have a dedicated return line. There are some systems that tend not to require a return line, although a return line can be very expensive to install. The cold water is used by these systems.
The pump is located at the fixture furthest from the water heater and is joined to the hot and cold water lines. When the pump is activated it pumps water from the water heater and then into the cold water line and on back to the water heater. When the pump discovers a rapid increase in temperature it shuts off, and hot water is now just a few seconds away after the tap is turned on.