diff --git a/src/configs/diffuser.json b/src/configs/diffuser.json
index 76b6454..014b80c 100644
--- a/src/configs/diffuser.json
+++ b/src/configs/diffuser.json
@@ -106,6 +106,34 @@
         "type": "number",
         "description": "Alpha factor used for oxygen transfer correction."
       }
+    },
+    "headerPressure": {
+      "default": 0,
+      "rules": {
+        "type": "number",
+        "description": "Header gauge pressure above atmospheric (mbar)."
+      }
+    },
+    "localAtmPressure": {
+      "default": 1013.25,
+      "rules": {
+        "type": "number",
+        "description": "Local atmospheric pressure (mbar)."
+      }
+    },
+    "waterDensity": {
+      "default": 997,
+      "rules": {
+        "type": "number",
+        "description": "Water density used in head-pressure calculation (kg/m3)."
+      }
+    },
+    "zoneVolume": {
+      "default": 0,
+      "rules": {
+        "type": "number",
+        "description": "Aeration zone volume used to convert oxygen output to reactor OTR (m3)."
+      }
     }
   }
 }