Understanding your buildings water use

Buildings naturally have different water usage intensities (WUI) depending on a combination of factors. The majority of residential water usage can be directly attributed to occupant activities such as flushing toilets, showering, food preparation, and cleaning. Modern building codes mandate that newly constructed buildings use high efficiency plumbing fixtures such as toilets, showers, and faucets, which results in newer buildings typically having lower WUI’s. In addition to these uses larger buildings can have shared systems which consume water for uses such as hydronic heating and cooling, pools, and irrigation.

Factors that can contribute to higher overall WUI include:

• Piping or equipment water leaks
• Indoor pools or hot tubs
• Higher occupant density
• Older less efficient plumbing fixtures such as toilets, shower heads and faucets.
• Top load washing machines and washing machines in suites.

Factors that can contribute to higher summer month WUI include:

• Landscape or planter irrigation and watering
• Outdoor pool or hot tub water evaporation
• Cooling towers which are frequently used for air conditioning on large buildings

What can be done to reduce water usage?

The following may help decrease the water usage of your building:

• Inspect and fix any existing water leaks, paying attention to toilet flapper leaks which often go undetected or ignored.
• Replacing older low efficiency toilets and faucets in common areas with modern high efficiency models. It may be possible to install flow restricting aerators on the existing faucets instead of replacing them completely.
• Educate owners on water use and the inefficiencies of older toilets, shower heads and faucets. Encourage owners to consider replacing older plumbing fixtures with newer more efficient models.
• Develop an opt-in replacement program for in-suite toilets to replace older inefficient models with newer high efficiency models.
• Develop an opt-in replacement program to install low flow aerators on suite faucets where applicable.

According to the water research foundation, toilets (24%) and showers (20%) account for the largest use of indoor residential water. Older plumbing fixtures can use significantly more water, so upgrading them to new high efficiency models typically results in a noticeable reduction of water use.

Consider the following:

• Toilets installed prior to 1990 typically use 2-4 times as much water as modern high efficiency toilets which use 6 liters per flush or less.
• Shower heads installed prior to 1990 typically use 1.5-2 times as much water as modern high efficiency models which use 9.5 liters per minute or less.