How the Water Calculator Works

How the WaterSense Calculator Works
This calculator was adapted from the WaterSense Calculator, a program of the U.S. Environmental Protection Agency (EPA). It provides basic information about household fixtures (faucets and/or toilets) that are installed or replaced with WaterSense labeled models and estimates the amount of water that you can expect to save with these products.
Water Usage Chart
The expected water savings are based on the billing of water and wastewater by various agencies on the Peninsula.
  • Newport News Waterworks bills for domestic water usage about every 60 days.
  • The Public Works’ Departments of Newport News and Hampton and the James city Service Authority use Waterworks’ meter reading to charge a “sewer user fee” to maintain local sewer lines. (York county and Poquoson charge a flat rate and bill quarterly.) The charges for sewer user fees vary by jurisdiction.
  • Hampton Roads Sanitation District (HRSD), uses Waterworks’ meter reading to charge for treatment of sewer waste.
The overall average for these charges to Peninsula residents is $10.61 per hundred cubic feet (hcf) and this is a good number to use when calculating the cost of water and sewer. It is derived from:
  • Waterworks rates (averaged, based on a typical household’s consumption of 11 hcf per billing period)
  • HRSD rates
  • Sewer User fees (averaged from the five jurisdictions, based on a typical household consumption).
Results
Estimates for expected energy savings are provided based on the current rate structure from Virginia Dominion Power and Virginia Natural Gas. Note that energy savings are only realized if faucets are being replaced, since faucets usually use warm water which requires electricity or natural gas to heat.
  • Hcf = hundred cubic feet (each hundred cubic feet = 748 gallons)
  • Kwh = kilowatts per hour
Assumptions
To provide estimated water and energy savings, the calculator assumes that all fixtures (e.g., faucets and/or toilets) within the household are being replaced or retrofitted with WaterSense labeled products.

It is assumed that the cost of one hundred cubic feet (hcf) of water (748 gallons) is about $10.61 for any Waterworks customer on the Peninsula (this includes Hampton, Newport News, and parts of James city county). This includes the average cost for sewer line maintenance and sewer treatment by other agencies. For Poquoson and York county, residential accounts are charged a flat fee and billed bimonthly.

To Estimate Gallons of Water Saved for Toilet Installations
The calculator determines the difference in gallons used by a WaterSense labeled toilet versus the toilet being replaced. WaterSense labeled toilets use 1.28 gallons of water per flush or less. Toilets installed before 1980 use about 5 gallons per flush. Toilets installed between 1980 and 1994 use about 3.5 gallons per flush, and toilets installed after 1994 use about 1.6 gallons per flush. The calculator multiplies the savings by the number of people in each household, and the time period specified by the user. The calculator also assumes an average of 5.05 flushes per person per day.

To Estimate Gallons of Water Saved for Faucet Installations
The calculator determines the difference in gallons used by a WaterSense labeled faucet (or the retrofit of an old faucet with a WaterSense labeled aerator) versus the faucet being replaced. It is assumed that use of a WaterSense labeled faucet, or the retrofit of an old faucet with a WaterSense labeled aerator, saves about 0.6 gallons per person per day. The calculator multiplies the savings by the number of people in each household, and the time period specified by the user.

To Estimate Energy Savings Associated with the Installation of WaterSense Labeled Faucets, or the Retrofit of Old Faucets with a WaterSense Labeled Aerators
The calculator determines how much it would cost to heat the water saved based on the selected energy source (e.g., natural gas or electricity), assuming that 73 percent of water that comes out of the tap in a typical household is heated. It is also assumed that the average cost of 1 cubic foot (cu ft) of natural gas is $0.01 and that the average cost of 1 kilowatt-hour (kwh) of electricity is $0.11 based on Virginia rates.
Finding WaterSense Labeled Products
When you use products bearing the WaterSense label, you can expect exceptional performance, savings on your water bills, and assurance that you are saving water for future generations. Look for the WaterSense label when buying plumbing fixtures.
Only products that are independently tested to meet EPA criteria for water efficiency and performance carry the WaterSense label.
  
Return to the WaterSense calculator.
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