You probably didn’t know you had a flow rate number, no worries most don’t. It’s only when it drops does anyone realize what they had is missing. Your home water flow rate is the measurement (gallons) of how fast treated water can come out of your faucets per minute.

In this blog, we’ll give you a better understanding of why flow rate is important, the basics of calculating water filter flow rate, and what is a normal flow rate.

## The Importance of Water Flow Rate

I can not express how important it is to know your desired flow rate. It’s key to picking the proper whole house water filtration your home is needing. It’s also important to select a water filter cartridge with a Gallons Per Minute Rating that is 2x the desired flow rate. This will result in the cartridge lasting closer to or up to the recommended six-month replacement time for maximum cost efficiency.

## Water Flow Rate Calculator

Let’s start off with what we are needing to determine flow rate.

**Pipe Diameter **is determined in two ways, I.D. which is the inside measurement and an O.D. is you guess it, the outside measurement. In this case the flow rate we are talking about is the I.D. Note that the larger the pipe’s diameter, the greater the water flow.

**Velocity** is the volume of water that passes through a given surface per unit of time.

**Flow Rate** is the rate which a volume of fluid flows through a closed container, example a pipe. It’s measured in **GPM** (gallon per minute) a unit of volumetric flow rate. Note that a slower flow rate is better for greater purification.

Looking at this sideways won’t help you, just saying. With every problem there is a solution, all you have to do is step back and start with what you know.

**KNOWN**

Pipe Diameter: the inside diameter measured in inches.

Volume Flow Rate: the rate which a volume of fluid flows through a closed container (i.e. a pipe).

The larger the pipe's diameter, the greater the water flow.

Velocity: the measure of how fast something is moves in a certain direction. Velocity = ft/sec.

For the best accuracy measure the flow 3 or 4 times and average the times together. The formula to find GPM is 60 divided by the seconds it takes to fill a one-gallon container (60 / seconds = GPM). Example: The one-gallon container fills in 5 seconds, breakdown: 60 divided by 5 equals 12 gallons per minute.

Note: 16 cups in a Gallon.

**UNKNOWN**

Flow Rate: the volume of water passing through it at any given time.

Flow rate = velocity x area (0.785xD2)

Gallon Per Minute (GPM): the amount of water that is coming from the unit.

Pounds Per Square Inch (PSI): the amount of pressure that the unit can produce with a clean filter.

OR there’s probably an app for that.

## How Many Gallons Per Minute Do You Need for Your Home?

This is a loaded question, that really comes down to preference and the number of individuals that are in the home. The average household needs 100 to 120 gallons per person per day, and a flow rate of about 6 to 12 gallons per minute.

A toilet will normally use about 2.2 to 5.0 GPM, a shower from 2.5 to 5.0 GPM, a bathtub from 4.0 to 8.0 GPM, a bathroom or kitchen faucet from 2.5 to 3.0 GPM, a dishwasher from 2.0 to 3.0 GPM, and a washing machine from 4.0 to 5.0 GPM.

Just keep in mind that every house actual flow rates and pressure drop will be determined based on cartridge selection and fluid viscosity.

Now that you have a better understanding of how to calculate water filter flow rate, and what a normal flow rate is, I would like to leave you with a **Pro Tip:** select a water filter cartridge with a Gallons Per Minute Rating that is 2x the desired flow rate. This will result in the cartridge lasting closer to or up to the recommended six-month replacement time for maximum cost efficiency.

For more information, check out our 'Choosing the Proper Water Filtration Solution'.