Thermostatic Mixing Valves Safely Regulate Water Temperatures in Challenging Commercial Plumbing Applications

By Ryan Pfund

Many of the plumbing codes that exist today are designed to prevent accidental scalding. While turning down the hot water heater may reduce injury potential in some cases, large multi-use buildings need a more effective solution.

Finding the right tempered water solution for a basic plumbing system with one water temperature is fairly straightforward. However, specifying valves for large commercial applications that have high water demands or widely varying water use can be more complicated.

Consider applications such as convention centers, sports stadiums, aquatic centers or large retailers in which water use is heavy during peak hours but slows to a trickle or sits idle for long periods of time. Another scenario: An older building that must have its plumbing brought up to code or upgraded to meet new uses while complying with environmental or historic preservation requirements.

Properly sizing and specifying a thermostatic mixing valve (TMV) may be the best solution for preventing water temperature extremes while accurately maintaining temperatures during low-use periods. Newer valve systems are making it easier than ever to install the right valve the first time.

Why TMVs?

Thermostatic valves are designed to control water temperatures at a safe level for showering, bathing and hand washing. Special valves are also used for emergency equipment such as eyewashes and drench showers. TMVs blend hot and cold water to preset temperatures to prevent users from burns and scalding. A key benefit is that water heaters can be turned up to hot temperatures (greater than 120 F) to prevent bacterial growth. Then, when a user activates the tap, hot water is blended with cold water to deliver a safe temperature to the faucet or shower.

TMVs are available in various shapes and sizes to meet the needs of different facilities. In some extremely large facilities several thermostatic mixing valves may be needed to meet the water demands of the building. For example, a hospital might require a high/low valve to deliver 140 F water to the cafeteria and laundry facilities, a high/low valve to deliver 120F water to the patient rooms or operating rooms, a point of use valve to provide 102 F water in the public restrooms, and an emergency mixing valve to provide a more tepid 80F temperature to the emergency fixtures in the lab.

Ultimately, the size of the valve depends on several factors such as the facility type and application, the number and types of fixtures to which the valve will provide water, the expected demand from those fixtures, the temperature of the water and the acceptable pressure loss that can be absorbed through the valve. 

Simplified Solutions for High-Demand Needs

Installing the proper valve system for extremely large facilities is becoming easier, thanks to new turnkey solutions offered by valve manufacturers. High-capacity manifold systems are designed specifically for applications that have a high demand for water. These valve systems have two high/low valves pre-assembled in parallel, in combination with a piping assembly and inlet/outlet shut-off valves, to handle water capacities as high as nearly 400 gallons per minute.

New products have also recently been introduced to simplify the installation of valves in hot water recirculation systems. All valve manufacturers have required installation methods to ensure that water temperatures are stable at all times, even with no draw from the plumbing system. These methods often require circulating pumps, balancing valves and check valves to be placed according to the manufacturers recommendations. If mistakes are made, or the methods not properly followed, water temperatures can spike overnight. Pre-assembled recirculation systems prevent this problem.

Recirculation stations may consist of a high/low valve combined with piping assembly; inlet/outlet shut-off valves; pressure/temperature gauges; circulation pump; balancing valve and an Aquastat. The entire system is assembled and tested before shipment, greatly simplifying the installation of a recirculation system. While plumbing engineers must still determine the pump and return line sizes, these engineered recirculation systems will simplify the specification and installation of a thermostatic valve in a domestic hot water distribution system and ensure components are installed in the proper location.

Tips for Sizing & Specifying TMVs

When selecting a TMV or complete system, consider installation and maintenance as part of the equation. TMVs that use single-valve technology, for example, have fewer connections than a multi-valve system, and require only one valve to set up and balance the system making installation quick and easy. A universal mounting capability further reduces installation time and costs.

When considering long-term maintenance, look for valve systems that are easy to service and are built to last. A reliable liquid-filled or wax-filled thermostat will require less maintenance in hard water, and some manufacturers will warrant them for as long as 10 years.

Online sizing tools can be helpful for specifying the appropriate valve for an application whether it's for a specific restroom or an entire building. Generally, these tools allow the user to input the minimum flow and acceptable pressure drop, then input the number of various fixtures that will be in the facility to get a product recommendation. Some programs will also size valves for a pure tempered water application where the user does not have final control of the water temperature.

When in doubt, contact the valve manufacturer to accurately size and specify the right thermostatic mixing valve for your particular application. If properly chosen, a thermostatic mixing valve can meet variable use demands and protect users from burns and scalding.

TMVs can be an effective solution for tempering water in challenging applications. The best TMV for your application may provide reduced installation and repair costs, as well as a reliable means to ensure users are protected against extreme temperatures.

Ryan Pfund is the Thermostatic Mixing Valve Product Manager at Bradley Corp., a leading manufacturer of plumbing fixtures, washroom accessories, partitions, emergency fixtures and solid plastic lockers. He can be reached at Bradley Corp., W142 N9101 Fountain Blvd., Menomonee Falls, WI, 53052. For more information, visit www.bradleycorp.com.