This clever device is used for for measuring water flow rates.
Useful when setting up combination boilers to help adjust the flow to the correct rate per minute.
Likewise useful when used in conjuction with our flow regulators and restrictors to measure pre and post flows.
When water flows through the gauge, the flow rate is measured from the calibrated slot. Calibrated 1/2 to 5 gallons per minute and 2.5 to 22 l/min.