Every month our customer service department will post one new question that has come up during the month that they believe will may help you troubleshoot an existing product or provide insight on a new product available.


No, you cannot use a “standard” thermostatic mixing valve with emergency fixtures (i.e. eye wash or drench shower). Most “standard” thermostatic mixing valves have inherent design features where if there ever was a failure of hot or cold to the inlets, the valve will reduce the output flow to a low flow. This scenario is very undesirable for emergency applications. Part of the principle behind emergency fixtures is to ensure that if someone has been exposed to hazardous materials always has water available to them to flush out the hazardous materials. All emergency mixing valves are specifically designed to be used with emergency eyewash/face wash/ and drench showering equipment. One of the unique features of this type of mixing valve is the integral cold water by-pass. The by-pass guarantees a minimum flow rate be delivered by the mixing valve with the cold water supply pressure as low as 30 PSI and the hot water supply pressure 0 or shutoff. For these applications, ANSI Z358.1 states that you must provide tepid (60-100°F) to the fixtures and emergency mixing valves provides a means to attain the designated temperature. Please note that ANSI provides a broad range because these are many chemicals in the market, and some may require a higher or lower temperature to provide soothing to the affected person. A Safety Compliance officer should consult a medical professional to confirm the appropriate drenching temperature based on their specific needs.

Minimum Flow is the lowest flow rate at which a valve will operate and still be able to maintain and supply an outlet temperature within specification. Usually it is very close or equal to the flow rate of one fixture operating within the facility, (i.e.. one lavatory sink has a 1 gpm flow rate). This is to allow temperature control if only one person is removing water from the system. It should also be noted that mixing valves only mix hot and cold water when water is being removed from the system. In regards to why some manufacturers state two minimums on their specification sheets, well, this a bit of smoke and mirrors. As stated before, all valves have a true minimum that they require to operate properly. Some manufactures offer single valves that may have higher minimum flows, and they try to utilize the recirculated tempered water to cover the minimum flow of the valve. There are occasions that you could likely do this, but it is critical to understand that if the recirculated flow is less than the actual minimum flow of the valve, then the mixing valve will be “seeking” and you will experience a lack of temperature control. Leonard Valve feels that attention to minimum flow is critical, and this was the driving force behind Leonard being the first manufacturer to design a two valve manifold system, where the small valve could temper for low demand and the larger valve tempers for the excess and high demands of a building. In this configuration, the small valve in our New Generation High/Low Systems all have a true minimum flow of 1.0 GPM, thus ensuring that we can temper for a single person bathing.

Likely not. For many thermostatic mixing valves, some simple maintenance can rejuvenate the mixing valve and return it to proper working condition. If you search for the installed model on our website, you will be able to download the product’s Operation & Maintenance Manual. With this manual, you will find a guide to performing the installation, maintenance and also the product’s parts breakdown. For your “stuck” valve, once you dissemble the valve, you can easily clean the components in a vinegar and water mixture, or use other cleaning products such as CLR, Lime-Away, etc. Allow the solution to clean the parts, rinse them off, and then you will be able to assemble and reset your valve the desired functional condition. We would also suggest that the mixing valve be placed on a standard maintenance schedule. With simple maintenance, and all mixing valves do require some level of maintenance, many valves can last for the life of the building.

The first and most important point of this discussion is that the balancing valve is the key to properly maintaining the domestic loop temperature during periods of no demand. It should be clearly noted that during times of no demand, you have a closed loop system. With no draw on the system, you cannot add additional cold water, so you have to utilize the return water and the stored hot water to maintain the desired loop temperature. It is the balancing valve that is the key. It allows for the proportional mix of the recirculated tempered water, and directs some of the return water back to the hot water source and some to the mixing valve. It is this blending (of constant return temperature water) that helps to maintains the domestic loop during times of no demand. At times of no demand, if you allowed 100% of the recirc water (tempered line) to return to the hot water tank, this would ultimately bring the domestic loop up to tank temperature. Conversely, if you closed the balancing valve and sent 100% of the recirc water back to the mixing valve, this would ultimately bring the domestic loop down to ambient temperature. It should be noted that different valves and manufactures may require alternate piping methods to handle the recirculated hot water, and you should always refer to the Operations & Maintenance Manual of that specific product to ensure that it is piped according to the manufacturer's suggested piping method.

Yes. If you refer to ASHRAE Guideline 12-2000 (“Minimizing the Risk of Legionellosis Associated with Building Water Systems”), in Section 4.1.6, it states "Where practical in health care facilities, nursing homes, and other high-risk situations, cold water should be stored and distributed at temperatures below 20°C (68°F), while hot water should be stored above 60°C (140°F) and circulated with a minimum return temperature of 51°C (124°F). However, great care should be taken to avoid scalding problems. One method is to install preset thermostatic mixing valves." You often see commercial building designs to include an ASSE 1017 approved master mixer to temper from the stored 140°F to 120°F for the domestic hot water loop. Often you will see additional devices, such as an ASSE 1070 approved Temperature Limiting Device at the lav's and an ASSE 1016 approved Shower Valve for their respective applications.

No. In general, the optimal condition is for inlet hot and cold pressures at the mixing valve to be equal. In some applications, such as when a water softener is used on the hot water side only, you can notice significant differences in pressure due to the pressure drop going through the softener. In these applications, you often see PRV’s installed to balance the inlet pressures.

No, we do not, nor does any other company. Unfortunatley there is a lot of misinformation in the market regarding the LEED® requirements and terminology. For LEED® (Leadership in Energy and Environmental Design), no products are “LEED® certified”, only buildings can become LEED® certified. Individual products can be used towards the calculation for specific sections of LEED®. For Leonard, we offer a low flow showerhead that provides 1.5 GPM of flow (which is a 40% reduction from the industry standard of 2.5 GPM). If you have specific questions on accreditation and other facets of LEED®, we suggest that you contact the U.S. Green Building Council directly at www.usbgc.org.


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