diff --git a/Arduino/CanGrow/CanGrow.ino b/Arduino/CanGrow/CanGrow.ino
index 7e08bf1..9482e03 100644
--- a/Arduino/CanGrow/CanGrow.ino
+++ b/Arduino/CanGrow/CanGrow.ino
@@ -499,9 +499,9 @@ int getWaterlevel() {
   * 0         : OK
   */
   
-  byte waterlevelWARN = 200;
-  byte waterlevelOK = 400;
-  byte waterlevelRAW = 0;
+  short waterlevelWARN = 200;
+  short waterlevelOK = 400;
+  short waterlevelRAW = 0;
   byte waterlevel = 0;
  
   // enable Vcc for water level sensor