Residential Water Use Calculator

Disclaimer

Using this calculator to estimate your water use for a WRIA 1 Adjudication Court Claim Form does not guarantee that the Washington Department of Ecology will accept the quantity submitted. Ecology retains the right to review all estimates and the Court will make all final decisions. This water use calculator is for general information only and based on federal guidance, state guidance, and/or other references. Calculations are estimates that may be sufficient in many circumstances but are not meant to reflect exact water usage. 

Whatcom County disclaims any warranty of merchantability or warranty of fitness of the information or data generated by this calculator for any particular purpose, either express or implied. No representation or warranty is made concerning the accuracy, currency, completeness or quality of data depicted. Any user of the calculator assumes all responsibility for use thereof, and further agrees to hold Whatcom County harmless from and against any damage, loss, or liability arising from any use of this calculator or the resulting data.

Overview

This calculator helps you estimate your residential water use for both indoor water use and small lawn/garden water use. For more information on how the water use estimates in this calculator were developed, please see the Residential Water Use Calculator Frequently Asked Questions. Your information in this online calculator is solely for your use and not saved or stored in any way. If you want to print this form for your own records, instructions are at the bottom of the page.

For Estimating Your Residential Water Use:

We provide two methods (one simple, the other more detailed) for estimating use:

  1. Simplified: Per capita water use estimate. This is based on Washington State Department of Health (DOH) and U.S. Environmental Protection Agency (EPA) guidelines of 60 gallons per day (GPD) per person for average residential water use. To use this, simply enter the number of people in your household into the "Required Question" field below and press “Calculate”. See your estimate at the bottom of the page.
  2. Detailed water use estimate. Based on feedback from residential water users requesting a more personalized water estimate tool, this method allows you to independently assess your specific water use by adding detailed information that you provide. Fill out both the "Required Question" field and as much as you can under the “Detailed Method Questions” section below and press “Calculate”. See your estimate at the bottom of the page.
Version 1.02, last updated 09/13/2024

Required Question (Needed for both Simplified and Detailed calculation methods.)
How many people (total) are in your household?

Detailed Method Questions

Please fill in these to the best of your ability. If you don’t know an answer, use the pre-loaded numbers (based on current Ecology and EPA water use guidelines and other resources) in the calculator fields.

Showers and Baths
How many showers are taken each day in your household?
  You can add whole numbers as well as a half value as needed e.g., “4” or “4.5”.
What is the average length (in minutes) of each shower?
  If you are not sure, enter 7.8 minutes per shower.
What is the flow rate (gallons per minute) of your showerhead?
  If you are not sure, enter 2.5 for low flow or 5 for standard (older shower heads.)
What is the total number of baths taken each week by members of your household?
What is the size of the bath (gallons)?
  If you are not sure, enter 30 gallons (based on 40-gallon capacity bathtub).

Toilets
What is the number of times each person flushes a toilet in your house per day?
  If you are not sure, enter 5 flushes per person.
How many gallons does your toilet use per flush?
  If you are not sure, enter 1.6 for low flow or 5 for standard (older toilets).

Faucets
How many total minutes each day are the faucets used (e.g., washing hands, brushing teeth, shaving, etc)?
  If you are not sure, enter 8 minutes.

Washing Dishes
How many total minutes each day are spent with the faucet running while washing dishes manually?
  If you are not sure, enter 15 minutes.
If you have a dishwasher, how many times is it used each week?
How many gallons of water per load does your dishwasher use?
  If you are not sure, enter 6.

Laundry
How many loads of laundry are done by members of your household each week?
How many gallons of water per load does your washing machine use?
  If you not unsure, enter 31.

Car Wash at Home
How many times a year do you wash your car(s) at home?
How many gallons of water per car wash do you use?
  If you’re not sure, enter 116.

Press the Calculate button to compute your estimated indoor residential water use.

Estimate Your Lawn and/or Garden Water Use

To use the lawn and garden calculator, simply enter the total size of your lawn and garden (combined size) in square feet. To find the size of your lawn/garden - go to the WRIA-1 Adjudication Resources Explorer and follow the instructions to draw and calculate your lawn or garden size.

Enter Lawn and/or Garden size

   Default value 10,890 sq ft (0.25 acres).

Press the Calculate button to compute your estimated Lawn/Garden Water Use.

Make Sure to Print + Save Your Work

When you are done calculating your water use using this calculator, make sure to save your work. Simply right click or press “Ctrl + p” to print. You can print as a PDF or print a hard copy, as you wish.