diff --git a/lorahandler.go b/lorahandler.go
index 18c6ad2..4216269 100644
--- a/lorahandler.go
+++ b/lorahandler.go
@@ -204,7 +204,8 @@ func WriteDatapoint(mytime int64, deveui string, devaddr string, v uint8, h uint
            alertLogMap[deveui] = fmt.Sprintf("alert,deveui=%s reason=\"swarmalarm\",w=%di,w_loss=%di %d\n",deveui,w_gram,w_loss,mytime*60*1000*1000*1000)
            location, _ := time.LoadLocation("Europe/Zurich")
            alertMap[deveui] = fmt.Sprintf("*** Schwarmalarm ***\n%s\n%s\nGewichtsverlust: %d g",getDevAlias(deveui),time.Unix(mytime*60,0).In(location).Format("02.01.2006 15:04"),w_loss)
-           
+           // alte Werte loeschen
+           deleteValues(deveui)
          }
      }
 }
diff --git a/persistence.go b/persistence.go
index f9ff1f3..21d6335 100644
--- a/persistence.go
+++ b/persistence.go
@@ -121,6 +121,17 @@ func addValue(deveui string, value uint16) {
         }
 }
 
+func deleteValues(deveui string) {
+        conn := globalPool.Get()
+        defer conn.Close()
+
+	_, err := conn.Do("LTRIM", lastvaluesPrefix + deveui, 1, 0)
+
+	if err != nil {
+		return
+        }
+}
+
 func getDevAlias(deveui string) string {
         res := deveui