diff --git a/src/main.cpp b/src/main.cpp
index eb46c13..af24181 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -55,10 +55,23 @@ float waterlevelMean[WATERLEVELMEAN_SIZE];
 uint16_t waterlevelMean_pos=0;
 
 
+// ######## Flow Rate
+#define FLOW_PIN 19
+uint16_t flow_counter=0; //maximum counts/s measured with Eden 128 Pump was 171
+void IRAM_ATTR isr_flow();
+unsigned long last_read_flow=0;
+#define READINTERVAL_FLOW 1000
+float flow_factor=7.5; //F=7.5*flowrate[L/min]
+float flow;
+
+uint32_t flow_counter_sum=0;
+
+
 unsigned long last_print=0;
 
 
 
+
 float getMean(uint16_t *parray,uint16_t psize);
 float getMeanf(float *parray,uint16_t psize);
 uint16_t getMin(uint16_t *parray, uint16_t psize);
@@ -127,6 +140,9 @@ void setup() {
   sensors.setResolution(thermometerAir, TEMPERATURE_PRECISION);
   
 
+  pinMode(FLOW_PIN, INPUT_PULLUP);
+	attachInterrupt(FLOW_PIN, isr_flow, CHANGE);
+
   Serial.println("Setup finished");
   delay(500);
 }
@@ -205,6 +221,17 @@ void loop() {
     waterlevelMean_pos%=WATERLEVELMEAN_SIZE;
   }
 
+
+  static uint16_t _last_flowconter; //for debugging
+  if (loopmillis>=last_read_flow+READINTERVAL_FLOW) {
+    flow=flow_counter*1000.0/(loopmillis-last_read_flow)/2.0; //Frequency [Hz]
+    flow/=flow_factor; //[L/min]
+    _last_flowconter=flow_counter; //for debugging
+  
+    flow_counter=0;
+    last_read_flow=loopmillis;  
+  }
+
   
   if (loopmillis>last_print+500) { 
     last_print=loopmillis;
@@ -225,6 +252,9 @@ void loop() {
     }else{
       Serial.print("\t waiting for distance");
     }
+
+    Serial.print("\t Flow="); Serial.print(flow,2); Serial.print(" ("); Serial.print(_last_flowconter); Serial.print(")");
+    Serial.print("\t Flowsum="); Serial.print(flow_counter_sum);
     
     
 
@@ -305,3 +335,9 @@ void printAddress(DeviceAddress deviceAddress)
     Serial.print(deviceAddress[i], HEX);
   }
 }
+
+
+void IRAM_ATTR isr_flow() {
+	flow_counter++;
+  flow_counter_sum++;
+}
\ No newline at end of file