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Dual Flush Toilets


Reduced Water Consumption

  • Uses 3L to 6L (0.7 to 1.3 gal1) per flush, compared to older toilets that can use 13L to 20L (3 to 4.4 gal) per flush.
  • Reduces water costs for tenant/owner where water is individually metered.
  • Reduces energy costs associated with water pumping for a home serviced by a well.
  • Reduces expenses associated with treatment and distribution of water in municipal systems.

Reduced Environmental Impact

  • Reduces amount of water drawn from surface or ground water.
  • Extends the life of septic system’s leach field by reducing water loading.
  • Reduces flows through municipal treatment systems.


  • Dual-flush toilets use low volumes of water to deal with liquid waste and higher volumes of water to deal with solid wastes.
  • Dual-flush toilets have low-flush capacities from 3 to 4 litres (0.7 to 0.9 gal) & high-flush capacities from 5 to 6 litres (1.1 to 1.3 gal) per flush. Most current models have 3L/6L (0.7/1.3 gal) flushes.
  • Power assist models are available to enhance flush performance.
  • Performance levels vary; seek out independent flush performance information. Look for products that have been independently tested and certified under programs such as WaterSense®.
  • Due to the more complex flushing mechanism, dual flush toilets can be slightly more expensive than traditional toilets.
  • They are designed with a larger trapway from the bowl, allowing water to flow out faster and more effectively clear the bowl.
  • With dual-flush toilets, it is important for waste pipes to have the proper slope (typically a slope of 2% (1/4 inch per foot)) to ensure proper drainage.
  • For retrofits, ensure the replacement toilet rough-in dimensions are the same as, or within, the original toilet dimensions to avoid having to change flooring and the location of the water supply pipe and drains.
  • When getting rid of your old toilet don’t give it away. Bring it to a landfill where it can be crushed and recycled into a new product.

1 1 litre = 0.22 Imperial gallons (or 0.26 US gallons in the USA)

Figure 1 — Dual-flush Toilet

A finger pushing one of the buttons to flush a dual flush toilet.

Figure 1 — Dual Flush Toilet

A dual-flush toilet seen from above, featuring the divided button for flushing on the top of the toilet tank.

What Does it Save?

Flushing toilets typically represents 40% of household water use, and changing out an older 13L (3 gal) toilet with a dual-flush unit that averages 4.8L (1.3 gal) per flush, can save up to 10% of a household’s overall water consumption.

Here is an example of the possible savings a family of four could see by replacing their 13L toilets with dual flush units. The example family flushes 4 times each per day. Over the course of a year, the 13L flushes send 75,900 litres down the drain. The savings associated with the dual flush toilet is roughly 47,890L (12,650 US gal) per year or 63% less than the 13L per flush toilet. The actual savings will depend on the volume of water used and the local cost of water.

Dual Flush Toilet Water Cost Saving

  Vancouver Calgary Toronto Montreal Halifax Whitehorse
2012 Water Costs Due to Toilte Flushing — 13L Flush 67 113 189 17 39 65
2012 Water Costs Due to Toilte Flushing — Dual Flush 25 72 70 6 15 24
Water Cost Savings $42 71 119 11 24 41

Depending on where you live, the amount of money you pay for water and sewage and how it is accounted for, varies. The trend in municipally serviced areas is towards metered water rates, so you pay a set amount per cubic meter of water used and that may include sewage treatment as well. You may live in an area where water rates are included in your tax assessment, or where you pay a flat rate on a monthly or annual basis. If you are outside of the municipal service area, then you are paying for the electricity to pump water into the house and a fee to have the septic tank pumped out every two to four years, depending on its size and your overall wastewater generation. Dual flush toilets can help reduce both costs.

For More Information

The information contained in this publication represents current research results available to CMHC. Readers are advised to evaluate the information, materials and techniques cautiously for themselves and to consult appropriate professional resources to determine whether information, materials and techniques are suitable in their case. The text is intended as general information only and project and site-specific factors of climate, cost, aesthetics, practicality, utility and compliance with applicable building codes and standards must be taken into consideration. A number of assumptions were applied with respect to fuel prices, water rates, costs of materials, equipment and labour, planning horizons, etc. Actual reductions in energy consumption and fuel savings will vary. Any reliance or action taken based on the information, materials and techniques described are the responsibility of the user. CMHC accepts no responsibility for consequences arising from the reader’s use of the information, materials and techniques herein.

Last revised: 2013



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