TheLEED for Homes Rating System (v4)addresses indoor water use in theWater Efficiency (WE) Credit: Indoor Water Use, which focuses on reducing water consumption through efficient plumbing fixtures (e.g., toilets, faucets, showerheads). Understanding the contribution of fixtures to total indoor water use is key to this credit.

According to theLEED Reference Guide for Homes Design and Construction (v4):

WE Credit: Indoor Water Use (1–6 points)

In a typical single-family home, plumbing fixtures (toilets, showerheads, and faucets) account for approximately two-thirds (2/3) of total indoor water use. Installing high-efficiency fixtures can significantly reduce water consumption.

Source: LEED Reference Guide for Homes Design and Construction, v4, Water Efficiency Credit: Indoor Water Use, p. 96.

TheLEED v4.1 Residential BD+Crating system confirms:

WE Credit: Indoor Water Use

Plumbing fixtures typically represent about 2/3 of indoor water use in single-family homes, making their efficiency critical for achieving water savings.

Source: LEED v4.1 Residential BD+C, Credit Library, accessed via USGBC LEED Online.

The correct answer is2/3(Option C), as plumbing fixtures account for approximately two-thirds of a typical single-family home’s indoor water use.

Why not the other options?

A. 1/3: This underestimates the contribution of plumbing fixtures, which are the primary indoor water users.

B. 1/2: This is closer but still underestimates the typical proportion (2/3).