Businesses are always looking to become more efficient, to save time and resources, which translates into savings. No matter how small, savings will add up for a business, especially if they get more use out of their equipment. One great method to become more efficient is through water use, or the amount of water used when flushing a toilet. It is a well-known fact that number 1’s require less water than number 2’s, so let’s talk about the dual flush system. Toilets with dual flush can flush with less water when there is less waste.
Quick history
The dual flush toilet was invented by Australian inventor Bruce Thompson in 1980. Its design proved that significant water savings can be achieved with this concept, and has since been adopted by a number of countries as a required spec for residential applications. Early designs required the replacement of the entire toilet, as the dual flush toilet used a gravity flush system instead of the prevalent siphon flush system; however, design improvements now allow for any toilet to be retrofitted with a dual flush system.
How it works
In tank type toilets, many dual flush systems work via two flaps in the tank. One flap is positioned on the bottom on the tank, and the other flap is at a predetermined height from the bottom of the tank (Fig 1, #32).
In this example, to flush liquid waste, lifting up on the handle would open the upper flap. This empties the water to the level of the upper flap (Fig 2, #34). At this point, the water now filling the bowl will raise the ball-cock, which then closes the upper flap.
Similarly, to flush solid waste, pushing down the handle would open the lower flap (Fig 3, #52). This empties the water to the level of the lower flap, at the bottom of the tank.
Since these improvements contribute to water savings in residential buildings, why not apply them to commercial applications? After all, commercial restrooms typically see much more use, so any savings would be significant. However, since commercial applications use flush valves instead of tank type flush systems, their dual flush capabilities rely on other methods to achieve the same goal. With flush valves, a specially designed handle activates a specially designed diaphragm or piston. These diaphragms and pistons have two positions to flush different amounts of water.
Sensor flush valves generally use the same components as manual flush valves, but they are designed without the handle. Instead, sensors will time how long someone is on the toilet, and use that to determine which flow rate to flush. Sensor diaphragm valves use the same diaphragm as their manual counterparts. Sensor piston valves, on the other hand, use a clever timing scheme to control the flush amount, meaning no special hardware (other than electronics) is needed.
Is it right for me?
One of the main downsides of dual flush systems is that they’re more expensive. However, the premium cost can be offset with the water saved, in certain circumstances. If your building has one or more of the following conditions, dual flush can be beneficial:
- There are women who use the toilet in your building – since women’s restrooms only have toilet fixtures, the toilets are used for both liquid and solid waste.
- There are only toilet fixtures in your building – most commercial buildings will have urinals installed in the men’s restrooms, but not always. If toilets are pulling double duty here, dual flush can help save water as well.
- There are shared (unisex) restrooms – this generally applies to smaller commercial establishments. If there are only a few restrooms that are shared by both genders, dual flush toilets will certainly help save water.
How much can it actually save?
The number of times a person uses the restroom in a day varies, but certifying organizations test with an average of 1 full flush and 2 low flushes per person, per day. In a typical building with dual flush in the women’s restroom, average savings is about 20% per flush, depending on the ratio of men and women that frequent the building. For a more information on the formulas used by the United States Green Building Council for their LEED program, please download our free water savings guide below.
