How to Ensure Your Tankless Water Heater Will Give You Endless Hot Showers

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Tankless water heaters promise the luxury of never-ending hot water, which is a major perk for people who like to take long showers. If a showerhead's flow rate is too low, however, it won't turn on a tankless water heater. Even though the heater may be fine, only cold water will come through the shower. If you're installing a tankless water heater in your home, here's how to make sure that your showerheads will activated it, so you will be able to take hours-long hot showers.

Activation Rates of Tankless Water Heaters

Tankless water heaters, unlike old-fashioned hot water tanks, have activation rates. An older tank would provide hot water whenever a hot-water faucet was turned on, regardless of how much water was being used. Tankless water heaters, in contrast, are only turned on if the demand for hot water exceeds their activation rate. They'll continue to provide hot water for as long as the flow is higher than their activation rate. If the flow never reaches their activation rate, though, they won't provide hot water.

To see how this works, you can turn on a sink's hot water in a home that has a tankless water heater. The water coming from the tap will be cold when the hot water is only set to a trickle, because the flow of water isn't greater than the heater's activation rate. When you turn the faucet all the way on, though, you'll quickly feel hot water -- the flow rate exceeds the activation rate.

If you're installing a tankless water heater in a single-family home, get a model that has a minimum activation rate of 0.5 gallons per minute. Some models that are used for residential purposes have activation rates of 0.75 gallons per minute.

Flow Rates of High-Efficiency Showerheads

The activation rate of a tankless water heater usually isn't an issue, because most faucets and appliances easily exceed it. Sinks, dishwashers and washing machines typically have higher flow rates than the activation rate.

Low-flow showerheads, however, sometimes have flow rates below a tankless water heater's activation rate. A Great Shower lists the flow rates for high-efficiency showerheads, showing their flow rates to be between 1.25 and 2.0 gallons per minute.

These figures are above the activation rates of residential tankless water heaters, but they still might not draw enough water to turn on a tankless water heater. Ultimately, flow rate decreases over distance. Therefore, a showerhead that has a flow rate of 1.25 gallons per minute might draw 1.25 gallons per minute if it's in a room adjacent to your tankless water heater.

If the showerhead is up three stories and on the other side of the home, however, the flow rate at the tankless water heater might be below 0.75 gallons per minute, even though the rate at the showerhead is higher. In this latter case, turning on the shower wouldn't turn on the tankless water heater, and you'd only have a cold shower.

Ways to Address Flow-Rate Issues

If your showerhead's flow rate isn't fast enough to activate a tankless water heater, you can still install the heater and enjoy endless hot showers. There are a few solutions you can try:

If you want to enjoy long hot showers, a tankless water heater will let you do that. Just make sure that your showerhead's flow rate will activate the water heater, so you can have hot water. Learn more by visiting resources like