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Water Conservation Opportunities in Multi-Residential Buildings

The chart below illustrates the water use in a typical multi-residential building.


Faucet Aerators typically allow 2.2 usgpm flow, but can be as high as 4 to 5 usgpm. Low flow Aerators are available, and range from 0.5 to 1.5 usgpm, with 1.0 usgpm used the most. They are available in Vandal Resistant (need a special tool to remove), Swivel and Dual Flow (that default back to low flow after faucet is turned off).

Shower Head flows range from 2.5 to 4 usgpm. Quality low flow shower heads are available for 1.5 usgpm.

Toilet Facts/Rules of Thumb:

  • Toilets use between 25% and 35% of all of the water in the building.
  • Most people flush 5-6 times per day while at home.
  • Leaks from toilets can result in 12% of the total water consumption and up to 200,000 l/yr.
  • Approximately 1 in 4 toilets are leaky.
  • Most older 13 Litre per flush have now been replaced by 6 lpf toilets. Newer 3 lpf and 4 lpf toilets are now available that meet the MaP (Maximum Performance) flush performance tests.
  • If the per suite cost for water is more than $300/yr, the building is a strong candidate for putting in new 3 lpf or 4 lpf toilets.

Toilet retrofits include:

  1. Replacement of toilets with 3 lpf and 4 lpf toilets. (About $250/toilet, including labour
  2. Ensure 6lpf toilets have proper early closure flappers (maintenance staff often replace leaky flappers with the improper type):
    1. Float flappers that have a small float about 6” above the flapper. Once the water drops to the float, the flapper starts to close.
    2. Hole flappers. They have a hole in the plug portion of the flapper that fills with water, allowing the flapper to close before the tank is completely drained.
  3. Refill Tube Clamp. This throttles the refill tube so that the bowl just fills enough. This saves up to 2lpf.
  4. Adjust fill line back to original design. If the fill is too low, people will double flush. If the fill is too high, it overflows the refill tube, resulting in a continuous leak.

Pipe leaks not only waste water, but they cause significant damages to the building. Replacing existing piping can be very expensive. It is possible, however, to fix pinhole leaks and to protect all of the piping against such leaks. Companies use food grade additive coating Sodium Silicate, which creates a protective coating on the pipe. The cost for the program is approximately $15K plus monthly costs between $300 and $800.


Scott Martin, P.Eng.