The Science of Mixing Valves

By Peter Gobis III

In 1961, Alan Shepard became the first American in space, JFK was inaugurated as president and Barbie got a new boyfriend named Ken. (Don’t worry, I only know this cute fact courtesy of Google.) In the land of mixing valves, things were pretty simple 50 years ago; if there was a two- inch domestic hot water line in the building, a two-inch valve was installed. Design principles have drastically changed since then, and a lot more science is incorporated into the utilization of various types of mixing valves in commercial buildings and into the mixing valve designs themselves.

The dictation by state and national codes to use certain types of mixing valves with specific installations is a trend that is significantly impacting the market. For those residing in a state that uses the International Plumbing Code (IPC), code compliance is paramount. A clear example of this is the mandate to use ASSE 1069 listed valves for gang shower applications. The American Society of Sanitation Engineers (ASSE) refers to 1069 valves as “automatic temperature control mixing valves that are intended to control the water temperature to individual or multiple fixtures to reduce the risk of scalding and thermal shock.”

These devices are intended to be installed in applications where the bather has no access to the temperature adjust means. With this in mind, the IPC has mandated their use in Section 424.4, which states, “Multiple (gang) showers supplied with a single-tempered water supply pipe shall have the water supply for such showers controlled by an approved automatic temperature control mixing valve that conforms to ASSE 1069 or CSA B125, or each shower head shall be individually controlled by a balanced-pressure, thermostatic or combination balanced-pressure/thermostatic valve that conforms to ASSE 1069 or CSA B125 and is installed at the point of use.” Very few manufacturers offer products that are listed to ASSE 1069; actually, only eight, so building designers have limited products to draw from for compliance to this requirement.

In addition to this requirement for gang showers, several other sections of the IPC dictate the use of certain types of mixing valves for specific applications. One such application is noted in Section 416.5, which states, “Tempered water shall be delivered from public hand-washing facilities. Tempered water shall be delivered through an approved water-temperature limited device that conforms to ASSE 1070 or CSA B125.3.” Designers and inspectors should research and reference the IPC for the specific requirements to ensure code compliance in their respective municipalities.

Beyond this example of how codes are driving design, technology advancements are certainly impacting market trends. All buildings have forms of mechanical and electrical services necessary for maintaining a comfortable working environment. Basic controls of these services used to take the form of manual switching, time clocks or temperature switches that provided the on and off signals for enabling pumps, fans and other devices.

Now, building managers are looking for more sophisticated applications to help in analyzing and managing these systems, and the arena has changed, with building management system (BMS) software.

The purpose of BMS software is to monitor and automate these systems’ operations in an efficient manner. The software also allows for support tools that enable facility managers to monitor, analyze and help in the decision making process for predictive maintenance and long-term building planning. In regards to mixing valves, this has lead to the development of interfaces that can collect water temperature and communicate this information in a language that the BMS can receive. This is accomplished by using protocols such as MODBUS® and BACnet®. Presently, there are only a couple of manufacturers that offer a product to interface with a building management system, but further integration will surely be developed as market demands create the need.

Trends towards energy management may also play a role in this market. With commercial buildings gobbling up nearly 20% of all energy used in the United States, some designers are looking to identify means to reduce energy cost. One such method being explored is to turn off the tempered water recirculation pump during long periods of no demand. With water heating accounting for around 7% of commercial energy cost, this philosophy may have its applications. One such building design that has seen some usage of this method is the elementary school, which experiences long periods of no demand.

Although this method may seem desirable for cost savings, facility managers and designers need to remain aware of Legionella concerns. Legionnaire’s Disease is a form of pneumonia bacteria that is present in many water systems. To help combat this deadly disease, it is important to keep water moving and also to store hot water at 140 F, because, after 32 minutes of exposure to this temperature, the bacteria will die off.

As these trends evolve, plumbing designers are being pushed and pulled to find a balance in their designs. You are being challenged to meet codes, to specify robust yet sustainable products and to meet aggressive budgets for building completion. Before your head starts to spin, don’t forget about that lead-free law that will be going national in 2014.

This is a very delicate and taxing situation that needs to result in the correct mix of products and design approach. Fortunately, a number of manufacturers employ best engineering practices and can offer solutions for these market demands for water temperature control devices.

Peter Gobis III is the national sales manager for the Leonard Valve Company.