diff --git a/configurations/home-assistant/configuration.yaml b/configurations/home-assistant/configuration.yaml
index b13f87a..014af9e 100644
--- a/configurations/home-assistant/configuration.yaml
+++ b/configurations/home-assistant/configuration.yaml
@@ -60,10 +60,11 @@ template:
         unit_of_measurement: "mm"
         state_class: measurement
         state: >
-          {% set sensor_offset = 2090 %}   {# distance (mm) from sensor to tank bottom #}
-          {% set distance = states('sensor.regenput_sensor_distance') | float(0) %}
-          {% set height = sensor_offset - distance %}
-          {{ [ [height, 0] | max, sensor_offset] | min | round(1) }}
+          {% set mount_gap = 290 %}         {# mm from sensor down to the "full" water line #}
+          {% set max_water_height = 2090 %} {# mm, tank depth from full line to bottom #}
+          {% set distance = states('sensor.cistern_distance') | float(0) %}
+          {% set height = max_water_height - (distance - mount_gap) %}
+          {{ [ [height, 0] | max, max_water_height] | min | round(1) }}
 
       - name: "Cistern Volume"
         unique_id: cistern_volume
@@ -82,6 +83,6 @@ template:
         unit_of_measurement: "%"
         state_class: measurement
         state: >
-          {% set sensor_offset = 2090 %}  {# same as above, = full tank height #}
+          {% set sensor_offset = 2090 - 290 %}  {# full tank height - sensor_mount #}
           {% set height = states('sensor.cistern_water_height') | float(0) %}
           {{ (height / sensor_offset * 100) | round(1) }}