Case Study: Dual-flush Toilets

Case Study: Dual-flush Toilets

by Rod Dempsey


My wife and I were raised in households where it was considered wasteful to dispose of anything that still worked well. However, this deep-rooted ethic has recently caused us some internal conflict over whether or not to replace two functional conventional toilets (13 litres per flush) with new dual- flush toilets (6 litres per flush for solids and 3 litres per flush for liquids).

The impetus for considering replacing the toilets in the first place was the $65 per toilet grant available through Natural Resources Canada’s ecoEnergy Retrofit program when we had an energy efficiency evaluation done on our home recently.

If our existing toilets suddenly ceased to work properly and had to be replaced, then there would be no conflict. They would be replaced and it would make sense to do so with dual- flush toilets (also known as high- efficiency toilets). However, this wasn’t the case – the existing toilets worked just fine.

What began to work on our minds, however, was the staggering difference in water consumption between a conventional toilet and a dual-flush toilet. If each person in our household of four people flushed a conventional toilet five times each day for one year, then 94,900 litres of water would be consumed.

Used to the same extent, a dual- flush toilet (assuming an average of 4.5 litres per flush) would consume 32,850 litres – a savings of 62,050 litres. This is the amount of water it would take to fill three backyard swimming pools measuring fifteen feet in diameter and four feet in depth.

So, what were we to do?

Not doing anything would keep more money in our pockets because even with the grant, installing two dual-flush toilets would still be an expense. Also, because residential water is not metered, there were no financial savings to be realized by conserving water – although, if you pump your own water from a well, you may save a few kilowatt-hours of electricity each year.

On the other hand, there were strong environmental reasons for conserving water – reasons that are increasingly becoming the basis of water conservation policies and practices in countries around the world. Also, because we have two school-aged children, there was the consideration as to what underlying message could be conveyed to them if dual-flush toilets were installed in our home. Would this help them to advance their environmental awareness and make them better environmental citizens in the future?

As you may have guessed by now, the rationale for water conservation won out and the dual- flush toilets were installed. The new toilets have been performing well; we have no regrets over our decision.