Proper flush valve installation calls for good, current information about how and where the unit will be used and how installing a flush valve differs from a tank installation.

In a flush valve installation, water flows under pressure from the supply piping directly to the fixture. The most common fixture with which flush valves are associated is the water closet. The required flow rate (gpm) is established by the hydraulics of the fixture—not the valve. If the supply pipes are properly sized, the water passing through the flush valve will permit the water closet to operate efficiently. In a tank, water is first accumulated in the tank from where the water flows by gravity to flush the fixture. Since flush valves rely on pressure and flow, they can reset faster than gravity tanks.

Flush valves are used to flush sanitary fixtures such as water closets, urinals, and service sinks, typically in commercial and industrial buildings. The flush valve provides a means to open the water supply line to a fixture, permitting a preset/preprogrammed volume of water to pass through it with the exact amount of water at the exact time to cleanse the fixture at each flush.

When installing any flush valve, it is important that the valve model matches the requirements of the plumbing fixture. The key to successful valve operation is to understand the type of installation and its environment and match the correct valve to the installation requirements.

Identifying your traffic type is the first step in determining which flush valve is right for your application. Determine your usage requirements by identifying your restroom-traffic patterns. Restroom usage can be classified under four basic traffic patterns:

  • High traffic, heavy abuse.
  • High traffic, normal abuse.
  • Low traffic, heavy abuse.
  • Low traffic, normal abuse.

Also consider water conditions because performance and reliability areoften compromised because of poor water quality. Dirty water, corrosive (salt) water, aggressive water, severe water conditions, treated water, and low water pressure are all factors.

Harsh operating environments can cause a flush valve that is not engineered to perform under these conditions to malfunction, or operate at low efficiency, which wastes water.

A recent amendment to the Americans with Disabilities Act (ADA) regulations may also affect your flush valve selection. This particularly affects the rear grab bar and its physical proximity to the flush valve. The proposed ADA Access Guidelines (ADAAG) (Federal Register, April 2, 2002)now address the use of split or shifted rear grab bars in the main text, as opposed to the current standard, which covers this topic in the Appendix (see ADAAG section A4.16.5). The proposed guidelines contain a ruling that allows rear grab bars to be split or shifted if local administrative authorities (local plumbing codes) require flush controls to be located in a position that conflicts with the location of the rear grab bar (see ADAAG section 604.5.2).

This clarification of the grab-bar requirements affects the specification and installation of flush valves that might cause interference or a tight fit between the valve and the rear grab bar. Fortunately, allowing the grab bar to be split or shifted to the wide side of the stall eliminates the need for offsetting flush valves that have higher installation heights (including those with bedpan washers and some sensor-operated valves) away from the wall so they are in front of the grab bar. While these valve models meet the requirements of the ADA, they do not meet the intent of the ADA requirements as they increase the possibility of the user coming in contact with the product. Such contact is addressed in Advisory 604.6, which appears in the proposed edition of the ADAAG.

ADAAG also permits the use of a shorter grab bar of 24 in. if wall space is not available for a 36-in. grab bar. The grab bar must be centered on the water closet (provided there is no interference with the flush controls as noted above). Where space permits, the additional length of the grab bar must be provided on the transfer side of the water closet. The age-specific height requirements for grab bars listed in ADAAG Section 604.9 are to be followed in conjunction with the other elements in the restroom. See last month’s article “ADA Primer for Specifying Flush Valves” by John Watson, July, 2004, for complete ADAAG requirements.

Another current issue is water conservation, driven both by regulations and the need for improved operating economies—especially in various parts of the world where the water supply is limited. This difference in flush valve construction is worthy of consideration. Today’s flush valves operate with lower water consumption than past models. Currently, the standard toilet fixture is 1.6 gpf, and the standard urinal is 1.0 gpf. A plumbing design strategy using 0.5-gpf urinals can impact usage and maximize water savings. This strategy has little or no associated costs and produces a rapid payback to the owner.

Flush valves are manufactured in two different designs: the diaphragm valve and the piston valve. The theory of operation in each is fundamentally the same. Each has an upper control chamber and a lower chamber connected by a bypass. The by-pass connecting the upper and lower chambers in both the diaphragm and piston valves is a small hole or orifice that is no larger than a pin hole, measuring between 0.020 in. and 0.030 in. diameter. A flexible diaphragm separates the upper from the lower chambers in diaphragm valve. A molded cup separates the upper from the lower chambers in the piston valve.

Each flush valve (diaphragm or piston type) can be operated manually (moving the handle to flush) or electronically (sensor-activated flush). The electronic mode provides a hands-free, automatic sensing fixture, which evacuates after every use. Reliable electronic control ensures easy access and use by the disabled, as well as enhanced hygiene.

Electronic designs can be further divided into transformer/hardwire, sensor-operated model or battery-powered models. Both provide the same functionality; the basic difference is that one needs wiring and the other needs batteries to function. The battery-operated model is recommended for space limited conditions or the owner’s personal preferences.

Power requirements can also be a deciding factor between the technologies. For example, some airport engineers specify both types of automatic flush valves (AFV): half hardwire and half battery-operated. In the event of any type of power failure, there are always functioning AFVs because the loss of power only affects the hardwire models.

Sensor-operated products require correct installation to properly target the user. If the sensor has been installed too high, too far to one side, or is crooked, the sensor may not be looking directly at the user. This can result in a sporadic pick-up due to the normal movement of a person in the stall. In more recent models, a technology called self-adaptive sensing is incorporated. This technology uses programming to basically “map” the area of service, and continuously make internal adjustments to accommodate range settings.

For example, if the sensor only picks up the edge of the user’s body, such as arms or head (instead of the trunk of the user for which the product is typically designed), then the sensor may perceive any movement of that person as a new user who is entering and leaving the detection zone. Consequently, every time movement occurs, an unwanted flush might be activated.

In addition, proper adjustment can also play a role in assuring that a sensor-operated valve only flushes when it should. While many sensor products are factory set, restroom environments can vary in size, shape, and other factors that can impact a sensor’s performance. And while many sensor products are equipped for manual adjustment and fine-tuning in the field to address these environmental differences, models utilizing self-adapting technology can eliminate the need for field adjustment.