Demand-Sensing Hot Water Recirculation Control

Smart Aquastat Recirculation Pump Control for Homes with a Dedicated Recirculation Loop and Tankless water heaters.

Satisfies CA Title 24 requirements

Smart Aquastat Control 32 for Tankless Water Heaters from Leridian Dynamics

The Smart Aquastat Control 32 is an “on-demand” smart hot water recirculating pump controller for homes with a tankless water heater or a Navien combi unit and a dedicated recirculation loop. If you don’t have a dedicated recirculation loop check out our Smart Thermostatic Control

Like all our controls, the Smart Aquastat Control has a flow meter that watches flow for flow and when detected is ensures the recirculation loop it hot. It differs from the Smart Recirculation Control in that it has only a single temperature sensor and turns the pump off when the single sensor reaches the configured temperature rather use the temperature difference between the water heater outflow and the return line.

When hot water is drawn from any plumbing fixture, if the temperature is below the low set point (default 100°F) it runs the recirculation pump until the water in the recirculation loop reaches the high set set point (default 105°F). The default values can be modified via the smart phone app. The microprocessor-based design monitors the temperature of the water returning in the recirculation loop to ensure the water in the loop stays hot while hot water is being used.

On demand hot water recirculation control system diagram animated image
To operate go to any faucet and turn the hot water on, then off.  The Smart Aquastat Control senses this minimal draw checks the water temperature in the loop, and if necessary, starts the pump running.  Within seconds the water loop is hot and you are able to draw hot water. 

Because the Smart Aquastat Control uses the demand of hot water to know when to run the pump, it works even when your washing machine or dishwasher needs hot water. 

Unlike other on-demand hot water systems, there is no need to install switches or sensors at each faucet location and run wires or maintain wireless transceivers.  

The Smart Aquastat Control also has a set of Smart Timers that can be used to heat the recirculation line on a schedule. 

The Smart Controller only runs the pump until the line is heated up to the programmed temperature.  

Of course, outside of the timer periods, the controller will still run the pump on demand.

The “Smart Timers” are disabled if the controller doesn’t sense a hot water draw within 24 hours.  So if you go on vacation and forget to manually disable them, no worries, they will turn themselves off and re-enable as soon as it senses a hot water draw.  The “Smart Timers”  are set via your Android or iPhone smart device.

Leridian Dynamics also makes a LEED for Homes v4 compliant on-demand Smart Aquastat Control 32.


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  1. For my particular case, it has far more features than necessary. Ideally, for me, I would prefer a simple turn the hot water on then off, then the pump would run for two and a half minutes. That’s it, all I need. No need for a temperature sensor, just want to keep the 6 – 8 gallons of water it takes before hot water gets to the back shower from going down the drain. To make sure the pump turns off, I put the sensor on the hot water pipe (not the return – to do that correctly, I would have to run 50 feet of phone wire, which I tried with some wire I had, but it did not work).