DOSING RETURN VALVE (DRV)A dosing return valve (DRV) directs the concentrate back to the tank and allows for easy recurring dosing testing of the system, without generating foam solution. This feature gives substantial savings over many years. No consumption of concentrate and no cost for cleaning or destruction of the solution after the test.One example: a 8000 lpm unit with 3% dosing rate. 4 tests/year at max speed for one minute. 8000 lpm x 3% = 240 liter of foam concentrate x 4 times = 960 liter at an average cost of 3 EUR/lit = 2880 EUR.- in saved cost/year. Apart from creating the long-time economic benefits, the optional DRV makes it easier to follow environmental guidelines and regulations. A Pressure relief valve (PRV) is always included with this DRV option to ensure no over-pressure is created in the FIREMIKS, if a valve in the return line back to concentrate tank is closed by mistake.FLOW CHART WITH OPTION DOSING RETURN VALVE (DRV)FLOW DIRECTION ON INSTALLATIONStandard flow direction is from left to right seen from pump side. Reversed water flow direction (right to left) or Vertical flow direction (upwards or downwards) is optional if specified when ordered.For more detailed optional features / items and Recommended Spare parts for 2-5 years, please consult the Data sheet for each model.