diff --git a/alyx/actions/tests.py b/alyx/actions/tests.py
index 989a2743..92b5711b 100644
--- a/alyx/actions/tests.py
+++ b/alyx/actions/tests.py
@@ -80,8 +80,10 @@ def test_water_control_thresholds(self):
         self.sub.save()
         wc = self.sub.reinit_water_control()
         wc.expected_weight()
-        self.assertAlmostEqual(self.wei[self.rwind], wc.reference_weight())
-        self.assertAlmostEqual(self.wei[self.rwind], wc.expected_weight())
+        # expected weight should be different to reference weight as the implant weight changes
+        expected = self.wei[self.rwind] + (wc.implant_weights[1][1] - wc.implant_weights[0][1])
+        self.assertAlmostEqual(expected, wc.reference_weight())
+        self.assertAlmostEqual(expected, wc.expected_weight())
         # test implant weight values
         self.assertEqual([4.56, 7.0], [x[1] for x in wc.implant_weights])
         self.assertEqual(7.0, wc.implant_weight())
@@ -91,23 +93,23 @@ def test_water_control_thresholds(self):
         self.sub.lab = Lab.objects.get(name='zscore')
         self.sub.save()
         wc = self.sub.reinit_water_control()
-        wc.expected_weight()
-        self.assertAlmostEqual(self.wei[self.rwind], wc.reference_weight())
         zscore = wc.zscore_weight()
+        self.assertAlmostEqual(zscore, 38.049183673469386)
+        self.assertEqual(zscore, wc.expected_weight())
         # test computation on mixed lab
         self.sub.lab = Lab.objects.get(name='mixed')
         self.sub.save()
         wc = self.sub.reinit_water_control()
-        self.assertAlmostEqual(self.wei[self.rwind], wc.reference_weight())
+        self.assertAlmostEqual(expected, wc.reference_weight())
         self.assertAlmostEqual(wc.expected_weight(), (wc.reference_weight() + zscore) / 2)
         # test that the thresholds are all above 70%
-        self.assertTrue(all([thrsh[0] > 0.4 for thrsh in wc.thresholds]))
+        self.assertTrue(all(thrsh[0] > 0.4 for thrsh in wc.thresholds))
         # if we change the reference weight of the water restriction, this should change in wc too
-        self.assertAlmostEqual(wc.reference_weight(), self.wr.reference_weight)
+        self.assertAlmostEqual(expected, wc.reference_weight())
         self.wr.reference_weight = self.wr.reference_weight + 1
         self.wr.save()
         wc = self.sub.reinit_water_control()
-        self.assertAlmostEqual(wc.reference_weight(), self.wr.reference_weight)
+        self.assertAlmostEqual(expected + 1, wc.reference_weight())
 
 
 class NotificationTests(TestCase):
diff --git a/alyx/actions/water_control.py b/alyx/actions/water_control.py
index cffe70e7..326412da 100644
--- a/alyx/actions/water_control.py
+++ b/alyx/actions/water_control.py
@@ -253,7 +253,10 @@ def reference_implant_weight_at(self, date=None, return_date=False):
         return self.last_implant_weight_before(wr or date, return_date)
 
     def reference_weighing_at(self, date=None):
-        """Return a tuple (date, weight) the reference weighing at the specified date, or today."""
+        """Return a tuple (date, weight) the reference weighing at the specified date, or today.
+
+        NB: this does not account for changes in implant weight.
+        """
         if self.reference_weighing and (date is None or date >= self.reference_weighing[0]):
             return self.reference_weighing
         date = date or self.today()
@@ -271,10 +274,16 @@ def reference_weighing_at(self, date=None):
         return ref_weight
 
     def reference_weight(self, date=None):
-        """Return the reference weight at a given date."""
+        """Return the reference weight at a given date.
+
+        NB: Unlike `reference_weighing_at` this accounts for changes in implant
+        weight.
+        """
         rw = self.reference_weighing_at(date=date)
         if rw:
-            return rw[1]
+            ref_iw = self.reference_implant_weight_at(date) or 0.
+            iw = self.last_implant_weight_before(date) or 0.
+            return (rw[1] - ref_iw) + iw
         return 0.
 
     def last_implant_weight_before(self, date=None, return_date=False):
@@ -414,7 +423,10 @@ def expected_water(self, date=None):
         weight = self.last_weighing_before(date=date)
         weight = weight[1] if weight else 0.
         expected_weight = self.expected_weight(date=date) or 0.
-        return 0.05 * (weight - iw) if weight < 0.8 * expected_weight else 0.04 * (weight - iw)
+        pct_sum = (self.reference_weight_pct + self.zscore_weight_pct)
+        # Increase required water by 0.01mL/g if weight below pct reference
+        pct_weight = (pct_sum * expected_weight)
+        return 0.05 * (weight - iw) if weight < pct_weight else 0.04 * (weight - iw)
 
     def given_water(self, date=None, has_session=None):
         """Return the amount of water given at a specified date."""
diff --git a/alyx/alyx/settings_lab_template.py b/alyx/alyx/settings_lab_template.py
index 29c2e836..9c10fabb 100644
--- a/alyx/alyx/settings_lab_template.py
+++ b/alyx/alyx/settings_lab_template.py
@@ -3,7 +3,7 @@
 # ALYX-SPECIFIC
 ALLOWED_HOSTS = ['localhost', '127.0.0.1']
 LANGUAGE_CODE = 'en-us'
-TIME_ZONE = 'Europe/London'
+TIME_ZONE = 'Europe/London'  # NB: Changing the timezone here requires migrations
 GLOBUS_CLIENT_ID = '525cc543-8ccb-4d11-8036-af332da5eafd'
 SUBJECT_REQUEST_EMAIL_FROM = 'alyx@internationalbrainlab.org'
 DEFAULT_SOURCE = 'IBL'