Dual-flush toilets flush too much, says Vancouver

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Bylaw amendment could make many models obsolete

By Leah Den Hartogh

The City of Vancouver plans to change the bylaws for dual-flush tank-type toilets because they are not saving enough water.

The expectation for these toilets is that for every three flushes, one is a large flush and two are small flushes. But this just isn’t happening, reports Chris Radziminski, water design branch for Vancouver, in an email. The Vancouver building bylaw currently allows a maximum flush rate of 4.8 litres per flush (LPF) for all toilet types.

However, in 2014 an exception was made for dual-flush tank-type toilets, permitting a full flush of 6 LPF and a small flush of 4.1 LPF. The new proposal would limit all toilets to 4.8 LPF and would eliminate about 90 per cent of the dual-flush tank-type toilets that are currently on the market from using city water, say industry officials. Most toilets – including over 2,000 single-flush tank-type toilet models – are entirely unaffected. The city’s proposal will allow the installation of 6 LPF dual-flush tank-type toilets in new construction projects, but only with treated rainwater or clear water waste (i.e. cooling water and condensate drainage from refrigeration and air-conditioning equipment) systems for flushing.

The Canadian Institute of Plumbing and Heating (CIPH) and the U.S.-based Plumbing Manufacturers International (PMI) dispute the fact that dual-flush tank-type toilets don’t meet performance expectations.

A Canada Mortgage and Housing Corporation study reports that the overall ratio was around 1.56 short flushes to every long flush. Akshay Sharma, program manager for CIPH, reports that this conclusion shows that there is water saving value with dual-flush tank-type toilets.

Reduced flush volumes

The most recent Vancouver water use bylaw changes, reducing the maximum flow rate of several plumbing products including residential lavatory faucets to 5.7 litres per minute (LPM) and showerheads to 7.6 LPM, came into effect in January 2018.

The new lower volume for dual-flush toilets, along with several other changes, is scheduled to take effect in January 2019.

“They really haven’t allowed the changes made in the 2017 bylaw amendments time to make an impact on their total per-capita water consumption,” noted Matt Sigler, technical director for PMI. Existing products that wouldn’t meet requirements would become obsolete as they could no longer be installed in new construction.

“Retailers again are going to have to restock shelves and account for these changes,” he said. Not enough time has passed for the city to receive proper statistics on how the initial bylaw went, adds Sigler

“It takes time to get those results of those reduced flow rate on water and energy consumption. You can’t expect it over night, it all depends on how many new structures are built in the city of Vancouver. It takes time.” Sigler suggests that at least three years would be needed to calculate the total impact.

PMI supports the use of non-potable water for toilet flushing. However, they believe there should be provisions to account for maximum chlorine levels when used with onsite non-potable water systems. They recommend that a maximum residual chlorine level of 2.5 milligrams per litre. If chlorine levels are too high, some plumbing products can fail. CIPH would also like to see a set level of 2.5 milligrams per litre, rather than determining it on a project to project basis.

However, said Radziminski, “The proposed requirement for non-potable water systems were developed in collaboration with the local health authority and are performance based. No specific type of disinfection is prescribed. This is the decision of the registered professional engineer who must design the system, and it is his/her responsibility to consider the local context.”

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