diff --git a/imports/energy_systems/water_to_water_hp_parameters.py b/imports/energy_systems/water_to_water_hp_parameters.py
index 8df8563f..e1cdaf55 100644
--- a/imports/energy_systems/water_to_water_hp_parameters.py
+++ b/imports/energy_systems/water_to_water_hp_parameters.py
@@ -79,11 +79,13 @@ class WaterToWaterHPParameters:
     :param ranges: the range of values to extract
     :return: List
     """
-    data = df.iloc[ranges[0]:ranges[1], columns[0]].append(df.iloc[ranges[0]:ranges[1], columns[1]])\
-      .append(df.iloc[ranges[0]:ranges[1], columns[2]])
+    data = pd.concat([df.iloc[ranges[0]:ranges[1], columns[0]], df.iloc[ranges[0]:ranges[1], columns[1]]])
+    data = pd.concat([df.iloc[ranges[0]:ranges[1], columns[2]], data])
     for i in range(1, 5):
-      data = data.append(df.iloc[ranges[i]:ranges[i + 1], columns[0]]).append(
-        df.iloc[ranges[i]:ranges[i + 1], columns[1]]).append(df.iloc[ranges[i]:ranges[i + 1], columns[2]])
+      data = pd.concat([df.iloc[ranges[i]:ranges[i + 1], columns[0]], data])
+      data = pd.concat([df.iloc[ranges[i]:ranges[i + 1], columns[1]], data])
+      data = pd.concat([df.iloc[ranges[i]:ranges[i + 1], columns[2]], data])
+
     return data.dropna().values.tolist()
 
   def _extract_flow_and_ewt(self, df, ranges, columns, flow_rates):