×

Proper Sizing Is Critical in Tankless Water Heater Installation

Last updated: June 1, 2026

Proper Sizing Is Critical in Tankless Water Heater Installation

Proper Sizing Is Critical in Tankless Water Heater Installation

When it comes to tankless water heater installation, proper sizing is one of the most important steps in making sure your system works as it should. A unit that is too small will struggle to meet demand, while one that is too large can be an unnecessary expense. Our team ensures every system is matched to your home’s needs through accurate calculations and professional installation.

Understanding Flow Rate

Flow rate is measured in gallons per minute (GPM) and tells us how much hot water a unit can produce at a given time. Determining the right flow rate starts with understanding your household’s usage. For example, running a shower, dishwasher, and washing machine at the same time requires a higher GPM than just a single faucet. If the unit’s flow rate is too low for your demand, you may experience temperature drops or inconsistent performance.

The Impact of Undersizing

Undersizing a tankless water heater can lead to several problems. The most common issue is the inability to provide hot water to multiple fixtures at once. You might notice your shower cooling down when the dishwasher is running. Over time, pushing an undersized unit beyond its limits can shorten its lifespan and increase the need for repairs.

The Problems With Oversizing

While it may seem safer to choose a larger unit, oversizing can also cause issues. A bigger system often means higher upfront costs and increased energy usage. In some cases, it can lead to cycling problems, where the unit turns on and off more frequently than needed, reducing efficiency and longevity. Proper sizing ensures you get the right balance between performance and operating cost.

How We Get It Right

Our team follows a clear process when sizing a tankless water heater. We assess your home’s water usage patterns, consider your climate, and calculate the necessary flow rate based on your fixtures and appliances. We then match you with a model that delivers reliable hot water without wasting energy or money. Professional installation also ensures all connections, venting, and controls are set up correctly for long-term performance.

If you want a reliable and efficient hot water solution, trust our team for tankless water heater installation. Call us at North Hill Sewer & Drain at (206) 202-3280 to get an estimate for tankless water heater installation in Redmond.

Written by Holly Smith Lead Plumbing Tech
12+ years experience
  • Specializes in sewer & drain systems
  • Serves Seattle, Des Moines, Auburn and Bellevue

Contact Us If You Have Any Plumbing Issues! (206) 202-3280