Which flush is which? Dual-flush fixtures should be better at making it obvious.

Editor's note: Thanks to Evan Dick for this guest post. Evan is a former writer from BuildingGreen and now works at the Center for EcoTechnology in Massachusetts.

The adage "If it's yellow let it mellow, if it's brown flush it down" might be an acceptable water-saving solution in some households, but certainly doesn't meet our expectations for cleanliness in more public throne rooms. Enter the dual-flush toilet, invented in 1980 by Bruce Thompson, an Australian working for bathroom products company Caroma. Dual-flush toilets have a full-flush option for solids and a partial-flush option for liquids. Each flush represents a measured and appropriate response to the waste-removal needs of the moment.

Unfortunately, flush controls on some models make it difficult to know which flush is which. Most of these toilets are in more public facilities, and getting busy, distracted people to understand and use the green design features we implement is a tricky problem, as we discussed in our recent feature on occupant engagement.

Confusing instructions

I used to get regular treatments from a Community Acupuncture Clinic in Tucson, Arizona.  Not wanting to be distracted during my treatment, I almost always used their restroom. The toilet was equipped with a perplexing dual-flush handle, and no instructions except a circle split down the middle, with one semicircle fully filled in and the other semicircle halfway filled in. This circle was located at the pivot point of the handle.

I was never sure which flush I was choosing.  Other models I have seen come with arrows or with stickers that can be placed on the tank to add further instruction.

Another type of lever uses a dual-action approach, where the main lever has a smaller lever within it that moves separately. The small lever moves independently for the half flush, and the large lever activates the full flush. However, because moving the large lever will also move the small lever, users can also find this confusing.

Pushing my buttons

While levers are common for dual-flush conversion kits, new dual-flush toilets are usually equipped with a push-button system. While these shiny chrome circles divided into two buttons look nice, they too fail the clarity-of-use test.

One side is usually larger than the other, representing the larger flush, but the size difference is slight enough that further instruction is often required. Some systems use equal-sized buttons with decals identifying which side is which. This is adequate, but could be problematic if the decals come off and are not replaced.

The most straightforward button system consists of two separate buttons, each manufactured with a full or half-full circle to direct the user. 

Potty training needed?

Maybe other folks are better potty-trained than I am, but an informal office survey found that other BuildingGreen employees had experienced similar confusion, with both the handle- and the button-controlled varieties.

The handles and buttons used for dual-flush toilets do important work and save water. That water savings should not be compromised by confusing design. If you have one of these toilets, simply adding an instructional sign, or making sure that markings on the controls are clear and well maintained should be enough to direct users to the right flush.

Looking for guidance on the most efficient dual-flush and regular-flush toilets? GreenSpec's listings of commercial toilets go a step beyond minimum federal standards, both in water efficiency and flushing performance.