diff --git a/packages/water_ph.yaml b/packages/water_ph.yaml
index c774d1dce849d0855a68bd9a37c8a4467622600f..b38ffba8de6935160017a6744dd7f610ed33afb0 100644
--- a/packages/water_ph.yaml
+++ b/packages/water_ph.yaml
@@ -13,10 +13,6 @@ globals:
     type: float
     restore_value: yes
     initial_value: ${ph700_raw}
-  - id: ph686_raw  # raw V value from probe using pH 6.86 calibration solution.
-    type: float
-    restore_value: yes
-    initial_value: ${ph686_raw}
   - id: ph918_raw # raw V value from probe using pH 9.18 calibration solution.
     type: float
     restore_value: yes
@@ -40,12 +36,6 @@ sensor:
   #   update_interval: 5s
   #   lambda: !lambda return id(ph400_raw);
   # - platform: template
-  #   name: "pH: 6.86 Calibration Value"
-  #   unit_of_measurement: "V"
-  #   accuracy_decimals: 5
-  #   update_interval: 5s
-  #   lambda: !lambda return id(ph686_raw);
-  # - platform: template
   #   name: "pH: 7.00 Calibration Value"
   #   unit_of_measurement: "V"
   #   accuracy_decimals: 5
@@ -65,20 +55,22 @@ sensor:
     update_interval: 5s
     lambda: |-
       float slope;
+      float intersect;
       if (id(ph_slope_points).active_index() == 1) {
-        slope = (id(ph918_raw) - id(ph400_raw)) / (9.18 - 4.00);
+        slope = (9.18 - 4.0) / ((id(ph918_raw)-1.5) / 3.0 - (id(ph400_raw)-1.5) / 3.0);
+        intersect =  9.18 - slope * (id(ph918_raw)-1.5) / 3.0;
       } else {
-        slope = (id(ph700_raw) - id(ph400_raw)) / (7.00 - 4.00);
+        slope = (7.0 - 4.0) / ((id(ph700_raw)-1.5) / 3.0 - (id(ph400_raw)-1.5) / 3.0);
+        intersect =  7.0 - slope * (id(ph700_raw)-1.5) / 3.0;
       }
-      float intersect = id(ph686_raw) - (slope * 6.86);
-      return (id(analog_ph).state - intersect) / slope;
+      return slope * (id(analog_ph).state-1.5) / 3.0 + intersect; 
 
 select:
   - platform: template
     id: ph_slope_points
     name: "pH: Calibration Points"
     options: ["4.00/7.00", "4.00/9.18"]
-    initial_option: "4.00/7.00"
+    initial_option: "4.00/9.18"
     optimistic: true
     restore_value: true
 
@@ -89,12 +81,6 @@ button:
       - globals.set:
           id: ph400_raw
           value: !lambda return id(analog_ph).state;
-  - platform: template
-    name: "pH: Calibrate 6.86"
-    on_press:
-      - globals.set:
-          id: ph686_raw
-          value: !lambda return id(analog_ph).state;
   - platform: template
     name: "pH: Calibrate 7.00"
     on_press: