By David Muir

There’s nothing worse than getting ready to take a shower and having to wait what seems like an eternity for hot water to come out of the shower head…standing there in your birthday suit repeatedly sampling the still cold water until you can finally tolerate the lukewarm spray.  If that’s a familiar situation in your house, you’ve likely learned to first run the faucet well before you undress and maybe even brush your teeth before testing the flow with your outstretched tootsies.

The main reason hot water takes a long time to reach the faucet is simply due to the distance between the water heater and the fixture.  The farther away a fixture is from the water heater, the longer it takes for the hot water to travel to it.  Also, cold pipes rob heat from the flow.  To make matters even worse, low volume flow restrictors are often installed on faucets and shower-heads.  While helping to conserve water, the slower flow they impose makes the journey from hot water tank to fixture even longer.  Fortunately, there are straightforward solutions to this problem, the simplest of which few people know about.

More is not the answer

Years ago, a popular solution to hasten the output of heated water was to install multiple hot water heaters at different locations throughout the house.  This remains a common practice in large, sprawling structures.  Alternatively, small supplemental water heaters can be installed closer to the point-of-use, like in a closet off the master bedroom. That was yesterday.

Tank-less Water Heaters

A more modern option to provide on-demand hot water is the tank-less hot water heater, offering an endless supply of hot water. Like the name implies, tank-less water heaters continually heat water in a large tank. Instead, when you open your tap, you send cold water over a powerful heating element inside a much smaller tank and it instantly becomes hot.  When you no longer need hot water and turn off the tap, the tank-less unit sort of goes to sleep until you need more. Since there is no hot water storage, thermal heat loss is nearly eliminated. This can significantly reduce your water heating costs. 

Now … back to the hot water delay problem I mentioned earlier: whole-house tank-less water heaters don’t solve the cold water blues either, but point-of-use tank-less water heaters DO. But as you’ll see, even they are not the best answer.

The smaller faucet-specific units are installed close to the fixture and they do provide a prompt flow of heated water. The drawback is they are rather expensive and installation can be quite involved.  Nevertheless, small tank-less heaters are a good option when one water heater doesn’t have the capacity to serve the entire home (like after a house extension). 

Best solution: A Hot Water Re-circulation System

The simplest and most effective solution to this problem is a hot water re-circulation system. This system works by slowly pumping hot water from the tank through the plumbing network and then back into the water heater. In this way, hot water is constantly available near every fixture throughout the house and, importantly, provides actual hot water to your washing machine and dishwasher at startup. 

When new houses are constructed, a hot water return pipe can be installed that runs all the way to the farthest fixture in the home and a small inline pump recirculates the water in a loop.  House builders now routinely include a dedicated re-circulation system into the plans of any sizable residence. In existing homes, however, it isn’t practical to install this return pipe. Instead, there is a similar design with a small pump at the water heater and an automatic valve installed at the farthest fixture in the home. The difference is that existing cold water piping is temporarily re-purposed to create a hot water re-circulation system. It’s a practical and ingenious solution to retrofit these systems into existing houses so you can take advantage of the benefits of hot water re-circulation. 

How Does It Work?

Think of how railroads keep priority trains moving and secondary ones out of the way all day long. They shunt some secondary trains onto unused rails when they want other stuff to go through. Keep that analogy in mind here.

The small pump at the water heater will maintain pressure pushing hot water through the pipes. Now, if no one in the house wants cold water, the valve on the hot water line at the end of your house activates and diverts that cooling hot water into the cold water pipes to flow backwards and return to the water heater to warm up again. This provides nearly instantaneous on-demand hot water.  When you open a cold water faucet again, the valve at the end of the house shuts itself down and you’ll experience a brief flow of diverted hot or lukewarm water before cool water arrives again.

There are several other system configurations available that achieve the same prompt supply depending on your needs and plumbing.  Hot water re-circulation systems not only conserve water, but also save money in the long run. A re-circulation pump is inexpensive (≈$300), small (grapefruit-size), uses little electricity and has a built-in timer to operate only as needed.  The pump is easily installed into, say, your hot water pipe and it plugs into a standard 110-volt outlet.  Every house should have one.  It’s especially a no-brainer to have a re-circulation system installed the same time replace your hot water heater.

I’ve introduced several friends to the retrofit system and all say – it’s a real game-changer.  I installed a retrofit system in my previous houses.  Fortunately, my house here in Marsh Creek (built in 2014) has a built-in hot water re-circulation system with a dedicated return line. After 10 years, the inaudible, 1/25 horsepower, 25-watt re-circulation pump is still going strong.