Plumbing Fixture Summary

About the Plumbing Fixture Summary

Summarizes a building's plumbing fixtures and estimates peak water demand using water supply fixture units (WSFU).

How to use this calculator

1. List each fixture type in the building, such as toilets, sinks, showers, and hose bibs.
2. Enter the number of each fixture and any demand value or fixture unit value if the calculator asks for it.
3. Let the calculator total the fixtures and combine the demand values.
4. Review the summary to see the overall fixture count and estimated water demand.

The formula explained

This tool combines fixture counts with their assigned demand values to estimate total water demand. The exact total depends on the fixture unit or flow values used for each fixture type.

• n = the number of fixtures of a given type
• d = the demand value for one fixture
• T = the total fixture demand or total load

Step by step method

1. Multiply each fixture count by its demand value to find the demand for that fixture type.
2. Add all fixture demands together to get the total.
3. If needed, also add all fixture counts to get the grand total number of fixtures.

Worked example

Problem. A small office has 4 lavatory sinks with a demand of 1.0 each, 2 toilets with a demand of 2.5 each, and 1 drinking fountain with a demand of 0.5. Find the total fixture demand and total fixture count.

1. Find each demand: for the sinks, \(4 \times 1.0 = 4.0\), for the toilets, \(2 \times 2.5 = 5.0\), and for the fountain, \(1 \times 0.5 = 0.5\).
2. Add the demands: \(4.0 + 5.0 + 0.5 = 9.5\).
3. Add the fixture counts: \(4 + 2 + 1 = 7\).

Tips and common mistakes

• Make sure you use the correct demand value for each fixture type, because different code tables may assign different values.
• Do not forget small fixtures, because they can still affect the total demand.

Frequently asked questions