Tankless water heaters don't only provide energy savings; they also give homeowners never-ending streams of hot water -- as long as their minimum flow rates are met. If their minimum flow rates aren't met, tankless water heaters won't provide any hot water. Therefore, if you're having a tankless water heater installed, you should first check your faucets' flow rates to make sure they meet or exceed your new water heater's minimum rate. You'll only enjoy unending hot water if they do meet the minimum rate.
Tankless Water Heaters Have Minimum Flow Rates
Unlike traditional hot water heaters, tankless models have a gauge that measures how quickly water is passing through them. While models with tanks will provide hot water no matter how much or little goes through them, tankless ones only start heating water when the water passing through their pipes exceeds a preset rate of gallons per minute (gpm).
For example, assume you have a tankless water heater with a minimum flow rate of 0.7 gpm. If you turn on the kitchen sink but draw only 0.5 gpm, you won't have any hot water. You'll only start feeling hot water once you begin using at least 0.7 gpm.
New Homes Generally Don't Have Flow-Rate Problems
In new home construction, flow rates typically aren't a problem. In theory, there could be an issue with a faucet using less water than a tankless water heater requires. Contractors are generally aware of this potential issue, though, and they know to use faucets and tankless water heaters that are compatible with one another.
Flow-Rate Issues Sometimes Arise in Existing Homes
In existing homes, however, flow-rate problems sometimes arise when replacing a traditional water heater with a tankless one. Homes with energy-efficient faucets that use less water are especially susceptible to flow-rate issues, as these faucets might use less water than a tankless water heater is designed for.
The likelihood of an issue arising increases in larger homes, because faucets can be further away from the tankless water heater. As M. Scott Greg notes, the flow rate decreases over distance, so faucets further from a water heater will have lower actual flow rates than identical faucets closer to the water heater. The flow rate diminishes with every additional foot of piping. Thus, a showerhead that has an official flow rate of 1 gpm might actually only draw 0.75 gpm of water if it's a significant distance away from the hot water heater.
Check Your Faucets' Flow Rates--And Adjust Them
Before paying a contractor to replace a traditional water heater with a tankless model, you should check the flow rates of your home's faucets. Every sink faucet, bathtub spout and showerhead should draw enough water to turn on your new tankless water heater. (The flow rates of toilets is less important, because toilets usually use only cold water.)
If your faucets' flow rates aren't high enough to turn on a tankless water heater, there are a few potential remedies that you could use:
- run multiple faucets simultaneously to increase your house's total flow rate
- replace the faucets with flow rates that are too low
- look for a different tankless water heater that has a lower minimum flow rate
- ask a plumber if they can adjust the minimum flow rate of the tankless water heater you are considering
As you look at tankless water heaters, make sure to also look at your faucets' flow rates. If they're lower than a model's minimum flow rates, there are several possible solutions. You can still get a tankless water heater. You'll want to address any flow-rate issues before you go to turn on the hot water, though. Contact a company like Smedley & Associates, Plumbing, Heating, Air Conditioning for more information.