diff --git a/api/s4_tanks.py b/api/s4_tanks.py
index 688e28a..45341fe 100644
--- a/api/s4_tanks.py
+++ b/api/s4_tanks.py
@@ -23,7 +23,9 @@ def get_tank_schema(name: str) -> dict[str, dict[str, Any]]:
 
 
 def get_tank(name: str, id: str) -> dict[str, Any]:
-    t = read(name, f"select * from tanks where id = '{id}'")
+    t = try_read(name, f"select * from tanks where id = '{id}'")
+    if t == None:
+        return {}
     xy = get_node_coord(name, id)
     d = {}
     d['id'] = str(t['id'])
@@ -99,6 +101,10 @@ def set_tank_cmd(name: str, cs: ChangeSet) -> DbChangeSet:
 
 
 def set_tank(name: str, cs: ChangeSet) -> ChangeSet:
+    if 'id' not in cs.operations[0]:
+        return ChangeSet()
+    if get_tank(name, cs.operations[0]['id']) == {}:
+        return ChangeSet()
     return execute_command(name, set_tank_cmd(name, cs))
 
 
@@ -120,6 +126,10 @@ def add_tank_cmd(name: str, cs: ChangeSet) -> DbChangeSet:
 
 
 def add_tank(name: str, cs: ChangeSet) -> ChangeSet:
+    if 'id' not in cs.operations[0]:
+        return ChangeSet()
+    if get_tank(name, cs.operations[0]['id']) != {}:
+        return ChangeSet()
     return execute_command(name, add_tank_cmd(name, cs))
 
 
@@ -141,6 +151,10 @@ def delete_tank_cmd(name: str, cs: ChangeSet) -> DbChangeSet:
 
 
 def delete_tank(name: str, cs: ChangeSet) -> ChangeSet:
+    if 'id' not in cs.operations[0]:
+        return ChangeSet()
+    if get_tank(name, cs.operations[0]['id']) == {}:
+        return ChangeSet()
     return execute_command(name, delete_tank_cmd(name, cs))
 
 
diff --git a/test_tjnetwork.py b/test_tjnetwork.py
index 41ab604..af59d46 100644
--- a/test_tjnetwork.py
+++ b/test_tjnetwork.py
@@ -646,6 +646,8 @@ class TestApi:
         p = 'test_tank'
         self.enter(p)
 
+        assert get_tank(p, 't0') == {}
+
         add_tank(p, ChangeSet({'id': 't0', 'x': 0.0, 'y': 10.0, 'elevation': 20.0, 'init_level': 1.0, 'min_level': 0.0, 'max_level': 2.0, 'diameter': 10.0, 'min_vol': 100.0, 'vol_curve': None, 'overflow': OVERFLOW_NO}))
         t0 = get_tank(p, 't0')
         assert t0['x'] == 0.0
@@ -706,6 +708,8 @@ class TestApi:
         nodes = get_nodes(p)
         assert len(nodes) == 0
 
+        assert get_tank(p, 't0') == {}
+
         add_tank(p, ChangeSet({'id': 't1', 'x': 0.0, 'y': 10.0, 'elevation': 20.0, 'init_level': 1.0, 'min_level': 0.0, 'max_level': 2.0, 'diameter': 10.0, 'min_vol': 100.0, 'vol_curve': None, 'overflow': OVERFLOW_NO}))
         add_tank(p, ChangeSet({'id': 't2', 'x': 0.0, 'y': 10.0, 'elevation': 20.0, 'init_level': 1.0, 'min_level': 0.0, 'max_level': 2.0, 'diameter': 10.0, 'min_vol': 100.0, 'vol_curve': None, 'overflow': OVERFLOW_NO}))
         add_tank(p, ChangeSet({'id': 't3', 'x': 0.0, 'y': 10.0, 'elevation': 20.0, 'init_level': 1.0, 'min_level': 0.0, 'max_level': 2.0, 'diameter': 10.0, 'min_vol': 100.0, 'vol_curve': None, 'overflow': OVERFLOW_NO}))