Technical Support

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.

Q: What does minimum flow refer to and why do some manufacturers state two minimum flows on their spec sheets?
A: 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.

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