# L 701.0 Method of Calculating Water Savings

Water use = (flow rate or consumption) × (duration) × (occupants) × (daily uses)

**TABLE L 701.2(1)WATER USE BASELINE ^{5}**

FIXTURE TYPE | MAXIMUM FLOW-RATE CONSUMPTION^{2} | DURATION | ESTIMATED DAILY USES PER PERSON | OCCUPANTS^{3,4} |
---|---|---|---|---|

Showerheads | 2.5 gpm at 80 psi | 8 minutes | 1 | — |

Private or Private Use Lavatory Faucets | 2.2 gpm at 60 psi | 0.25 minutes | 4 | — |

Residential Kitchen Faucets | 2.2 gpm at 60 psi | 4 minutes | 1 | — |

Wash Fountains | One 2.2 gpm at 60 psi fixture fitting for every 20 inches rim space | — | — | |

Lavatory Faucets in other than Residences, Apartments, and Private Bathrooms in Lodging Facilities | 0.5 gpm | 0.25 minutes | 4 | — |

Metering Faucets | 0.25 gallons /cycle | — | 3 | — |

Metering Faucets for Wash Fountains | One 0.25 gallon per cycle fixture fitting for every 20 inches rim space | — | — | — |

Water Closets | 1.6 gallons per flush | 1 flush | 1 male^{1} | — |

3 female | — | |||

Urinals | 1.0 gallons per flush | 1 flush | 2 male | — |

For SI units: 1 gallon per minute = 0.06 L/s, 1 pound-force per square inch = 6.8947 kPa, 1 gallon = 3.785 L, 1 inch = 25.4 mm

**Notes:**

^{1} The daily use number shall be increased to three where urinals are not installed in the room.

^{2} The maximum flow rate or consumption is from the Energy Policy Act.

^{3} For residential occupancies, the number of occupants shall be based on two persons for the first bedroom and one additional person for each additional bedroom.

^{4} For non-residential occupancies, refer to Table 422.1 for occupant load factors.

^{5} Where determining calculations, assume one use per person for metering or self-closing faucets.

**TABLE L 701.2(2)WATER SAVINGS CALCULATOR ^{1, 2, 3}**

NON-RESIDENTIAL BUILDINGS | |||||
---|---|---|---|---|---|

FIXTURE TYPE | CONSUMPTION (gallons per minute) | DAILY USES | DURATION (minutes) | OCCUPANTS | DAILY WATER USES (gallons) |

1.6 gpf (gallons per flush) toilet - male | 1.6 | 1 | 1 | 150 | 240 |

1.6 gpf toilet - female | 1.6 | 3 | 1 | 150 | 720 |

1.0 gpf urinal - male | 1 | 2 | 1 | 150 | 300 |

Commercial lavatory faucet - 0.5 gpm | 0.5 | 3 | 0.25 | 300 | 113 |

Kitchen sink - 2.2 gpm | 2.2 | 1 | 0.25 | 300 | 165 |

Showerhead - 2.5 gpm | 2.5 | 0.1 | 8 | 300 | 600 |

Total Daily Volume | 2138 | ||||

Annual Work Days | 260 | ||||

Total Annual Usage | 555 750 |

NON-RESIDENTIAL BUILDINGS | |||||
---|---|---|---|---|---|

FIXTURE TYPE | CONSUMPTION (gallons per minute) | DAILY USES | DURATION (minutes) | OCCUPANTS | DAILY WATER USES (gallons) |

1.6 gpf toilet - male | 1.28 | 1 | 1 | 150 | 192 |

1.6 gpf toilet - female | 1.28 | 3 | 1 | 150 | 576 |

1.0 gpf urinal - male | 0.5 | 2 | 1 | 150 | 150 |

Commercial lavatory faucet - 0.5 gpm | 0.5 | 3 | 0.25 | 300 | 113 |

Kitchen sink - 2.2 gpm | 2.2 | 1 | 0.25 | 300 | 165 |

Showerhead - 2.5 gpm | 2.5 | 0.1 | 8 | 300 | 600 |

Total Daily Volume | 1796 | ||||

Annual Work Days | 260 | ||||

Total Annual Usage | 466 830 | ||||

Annual Savings | 88 920 | ||||

% Reduction | —16.0 percent |

For SI units: 1 gallon per minute = 0.06 L/s, 1 gallon = 3.785 L

**Notes:**

^{1} Consumption values shown as underlined reflect the maximum consumption values associated with the provisions called out in the IAPMO Green Plumbing & Mechanical Code Supplement.

^{2} Where metering faucets are used, insert the flow rate of the faucet in the "Consumption" column and insert the cycle time in the "Duration" column (assume 1 cycle per use).

^{3} To determine estimated savings, insert occupant values (same as Baseline) and consumption values based on fixtures and fixture fittings installed.

**TABLE L 701.2(2) (continued)WATER SAVINGS CALCULATOR ^{1, 2}**

NON-RESIDENTIAL BUILDINGS | |||||
---|---|---|---|---|---|

FIXTURE TYPE | CONSUMPTION (gallons per minute) | DAILY USES | DURATION (minutes) | OCCUPANTS | DAILY WATER USES (gallons) |

1.6 gpf toilet | 1.6 | 5 | 1 | 4 | 32 |

Lavatory faucet - 2.2 gpm | 2.2 | 8 | 0.25 | 4 | 18 |

Kitchen sink - 2.2 gpm | 2.2 | 6 | 0.25 | 4 | 13 |

Showerhead - 2.5 gpm | 2.5 | 0.75 | 8 | 4 | 60 |

Total Daily Volume | 123 | ||||

Annual Work Days | 44 822 |

NON-RESIDENTIAL BUILDINGS | |||||
---|---|---|---|---|---|

FIXTURE TYPE | CONSUMPTION (gallons per minute) | DAILY USES | DURATION (minutes) | OCCUPANTS | DAILY WATER USES (gallons) |

1.6 gpf toilet - male | 1.28 | 5 | 1 | 4 | 26 |

Lavatory faucet - 1.5 gpm | 1.5 | 8 | 0.25 | 4 | 12 |

Kitchen sink - 2.2 gpm | 2.2 | 6 | 0.25 | 4 | 13 |

Showerhead - 2.5 gpm | 2.5 | 0.75 | 8 | 4 | 60 |

Total Daily Volume | 111 | ||||

Annual Usage | 40 442 | ||||

Annual Savings | 4380 | ||||

% Reduction | -9.8 percent |

For SI units: 1 gallon per minute = 0.06 L/s, 1 gallon = 3.785 L

**Notes:**

^{1} Consumption values shown as underlined reflect the maximum consumption values associated with the provisions called out in the IAPMO Green Plumbing & Mechanical Code Supplement.

^{2} To determine estimated savings, insert occupant values (same as Baseline) and consumption values based on fixtures and fixture fittings installed.

**Notes and instructions for Table L 701.2(2):**

Table L 701.2(2) is an example of a calculator that is capable of helping estimate water savings in residential and nonresidcntial structures. The "Duration" of use and "Daily Uses" values that appear in the table are estimates and based on previous studies. The first example shown below is a commercial office building with 300 occupants, 150 females, and 150 males. The second example is a 3 bedroom residential building. To obtain and use a working copy of this calculator, follow the download and use instructions below.

Instructions for download:

- Go to the IAPMO website at www.iapmogreen.org to download the water savings calculator. The calculator is a Microsoft Office Excel file (1997 or later), your computer must be capable of running MS Excel.
- Follow the instructions for downloading and running the file.

Instructions for use:

- In the Baseline Case section, insert the number of total occupants, male occupants and female occupants that apply to the building in the "Occupants" column. Unless specific gender ratio values are provided, assume a 50/50 gender ratio.
- Copy and paste these same values in the "Occupants" column of the Calculator section.
- In the Calculator section, insert the consumption values (flow rates in gpm or gallons per flush or per cycle) in the "Consumption" column.
- Estimated water savings regarding percent savings versus baseline values, gallons per day and gallons per year will be automatically calculated.

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