diff --git a/api/__init__.py b/api/__init__.py
index 9b808e0..8ec20d6 100644
--- a/api/__init__.py
+++ b/api/__init__.py
@@ -65,6 +65,9 @@ from .s17_quality import get_quality_schema, get_quality, set_quality
 from .s18_sources import SOURCE_TYPE_CONCEN, SOURCE_TYPE_MASS, SOURCE_TYPE_FLOWPACED, SOURCE_TYPE_SETPOINT
 from .s18_sources import get_source_schema, get_source, set_source, add_source, delete_source
 
+from .s20_mixing import MIXING_MODEL_MIXED, MIXING_MODEL_2COMP, MIXING_MODEL_FIFO, MIXING_MODEL_LIFO
+from .s20_mixing import get_mixing_schema, get_mixing, set_mixing, add_mixing, delete_mixing
+
 from .s21_times import TIME_STATISTIC_NONE, TIME_STATISTIC_AVERAGED, TIME_STATISTIC_MINIMUM, TIME_STATISTIC_MAXIMUM, TIME_STATISTIC_RANGE
 from .s21_times import get_time_schema, get_time, set_time
 
diff --git a/api/s20_mixing.py b/api/s20_mixing.py
new file mode 100644
index 0000000..bf3eb06
--- /dev/null
+++ b/api/s20_mixing.py
@@ -0,0 +1,96 @@
+from .operation import *
+from .s0_base import *
+
+MIXING_MODEL_MIXED = 'MIXED'
+MIXING_MODEL_2COMP = '2COMP'
+MIXING_MODEL_FIFO = 'FIFO'
+MIXING_MODEL_LIFO = 'LIFO'
+
+def get_mixing_schema(name: str) -> dict[str, dict[str, Any]]:
+    return { 'tank'  : {'type': 'str'   , 'optional': False , 'readonly': True },
+             'model' : {'type': 'str'   , 'optional': False , 'readonly': False},
+             'value' : {'type': 'float' , 'optional': True ,  'readonly': False} }
+
+
+def get_mixing(name: str, tank: str) -> dict[str, Any]:
+    m = read(name, f"select * from mixing where tank = '{tank}'")
+    d = {}
+    d['tank'] = str(m['tank'])
+    d['model'] = str(m['model'])
+    d['value'] = float(m['value']) if m['value'] != None else None
+    return d
+
+
+class Mixing(object):
+    def __init__(self, input: dict[str, Any]) -> None:
+        self.type = 'mixing'
+        self.tank = str(input['tank'])
+        self.model = str(input['model'])
+        self.value = float(input['value']) if 'value' in input and input['value'] != None else None
+
+        self.f_type = f"'{self.type}'"
+        self.f_tank = f"'{self.tank}'"
+        self.f_model = f"'{self.model}'"
+        self.f_value = self.value if self.value != None else 'null'
+
+    def as_dict(self) -> dict[str, Any]:
+        return { 'type': self.type, 'tank': self.tank, 'model': self.model, 'value': self.value }
+
+    def as_id_dict(self) -> dict[str, Any]:
+        return { 'type': self.type, 'tank': self.tank }
+
+
+def set_mixing_cache(name: str, cs: ChangeSet) -> SqlChangeSet:
+    old = Mixing(get_mixing(name, cs.operations[0]['tank']))
+    raw_new = get_mixing(name, cs.operations[0]['tank'])
+
+    new_dict = cs.operations[0]
+    schema = get_mixing_schema(name)
+    for key, value in schema.items():
+        if key in new_dict and not value['readonly']:
+            raw_new[key] = new_dict[key]
+    new = Mixing(raw_new)
+
+    redo_sql = f"update mixing set model = {new.f_model}, value = {new.f_value} where tank = {new.f_tank};"
+    undo_sql = f"update mixing set model = {old.f_model}, value = {old.f_value} where tank = {old.f_tank};"
+
+    redo_cs = g_update_prefix | new.as_dict()
+    undo_cs = g_update_prefix | old.as_dict()
+
+    return SqlChangeSet(redo_sql, undo_sql, redo_cs, undo_cs)
+
+
+def set_mixing(name: str, cs: ChangeSet) -> ChangeSet:
+    return execute_command(name, set_mixing_cache(name, cs))
+
+
+def add_mixing_cache(name: str, cs: ChangeSet) -> SqlChangeSet:
+    new = Mixing(cs.operations[0])
+
+    redo_sql = f"insert into mixing (tank, model, value) values ({new.f_tank}, {new.f_model}, {new.f_value});"
+    undo_sql = f"delete from mixing where tank = {new.f_tank};"
+
+    redo_cs = g_add_prefix | new.as_dict()
+    undo_cs = g_delete_prefix | new.as_id_dict()
+
+    return SqlChangeSet(redo_sql, undo_sql, redo_cs, undo_cs)
+
+
+def add_mixing(name: str, cs: ChangeSet) -> ChangeSet:
+    return execute_command(name, add_mixing_cache(name, cs))
+
+
+def delete_mixing_cache(name: str, cs: ChangeSet) -> SqlChangeSet:
+    old = Mixing(get_mixing(name, cs.operations[0]['tank']))
+
+    redo_sql = f"delete from mixing where tank = {old.f_tank};"
+    undo_sql = f"insert into mixing (tank, model, value) values ({old.f_tank}, {old.f_model}, {old.f_value});"
+
+    redo_cs = g_delete_prefix | old.as_id_dict()
+    undo_cs = g_add_prefix | old.as_dict()
+
+    return SqlChangeSet(redo_sql, undo_sql, redo_cs, undo_cs)
+
+
+def delete_mixing(name: str, cs: ChangeSet) -> ChangeSet:
+    return execute_command(name, delete_mixing_cache(name, cs))
diff --git a/test_tjnetwork.py b/test_tjnetwork.py
index bdbe242..562b414 100644
--- a/test_tjnetwork.py
+++ b/test_tjnetwork.py
@@ -2576,6 +2576,125 @@ class TestApi:
         self.leave(p)
 
 
+    # 20 mixing
+
+
+    def test_mixing(self):
+        p = 'test_mixing'
+        self.enter(p)
+
+        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}))
+
+        add_mixing(p, ChangeSet({'tank': 't0', 'model': MIXING_MODEL_MIXED, 'value': 10.0}))
+        m = get_mixing(p,'t0')
+        assert m['tank'] == 't0'
+        assert m['model'] == MIXING_MODEL_MIXED
+        assert m['value'] == 10.0
+
+        set_mixing(p, ChangeSet({'tank': 't0', 'model': MIXING_MODEL_2COMP}))
+        m = get_mixing(p,'t0')
+        assert m['tank'] == 't0'
+        assert m['model'] == MIXING_MODEL_2COMP
+        assert m['value'] == 10.0
+
+        set_mixing(p, ChangeSet({'tank': 't0', 'value': 20.0}))
+        m = get_mixing(p,'t0')
+        assert m['tank'] == 't0'
+        assert m['model'] == MIXING_MODEL_2COMP
+        assert m['value'] == 20.0
+
+        delete_mixing(p, ChangeSet({'tank': 't0'}))
+
+        self.leave(p)
+
+
+    def test_mixing_op(self):
+        p = 'test_mixing_op'
+        self.enter(p)
+
+        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}))
+
+        cs = add_mixing(p, ChangeSet({'tank': 't0', 'model': MIXING_MODEL_MIXED, 'value': 10.0})).operations[0]
+        assert cs['operation'] == API_ADD
+        assert cs['type'] == 'mixing'
+        assert cs['tank'] == 't0'
+        assert cs['model'] == MIXING_MODEL_MIXED
+        assert cs['value'] == 10.0
+
+        cs = execute_undo(p).operations[0]
+        assert cs['operation'] == API_DELETE
+        assert cs['type'] == 'mixing'
+        assert cs['tank'] == 't0'
+
+        cs = execute_redo(p).operations[0]
+        assert cs['operation'] == API_ADD
+        assert cs['type'] == 'mixing'
+        assert cs['tank'] == 't0'
+        assert cs['model'] == MIXING_MODEL_MIXED
+        assert cs['value'] == 10.0
+
+        cs = set_mixing(p, ChangeSet({'tank': 't0', 'model': MIXING_MODEL_2COMP})).operations[0]
+        assert cs['operation'] == API_UPDATE
+        assert cs['type'] == 'mixing'
+        assert cs['tank'] == 't0'
+        assert cs['model'] == MIXING_MODEL_2COMP
+        assert cs['value'] == 10.0
+
+        cs = execute_undo(p).operations[0]
+        assert cs['operation'] == API_UPDATE
+        assert cs['type'] == 'mixing'
+        assert cs['tank'] == 't0'
+        assert cs['model'] == MIXING_MODEL_MIXED
+        assert cs['value'] == 10.0
+
+        cs = execute_redo(p).operations[0]
+        assert cs['operation'] == API_UPDATE
+        assert cs['type'] == 'mixing'
+        assert cs['tank'] == 't0'
+        assert cs['model'] == MIXING_MODEL_2COMP
+        assert cs['value'] == 10.0
+
+        cs = set_mixing(p, ChangeSet({'tank': 't0', 'value': 20.0})).operations[0]
+        assert cs['operation'] == API_UPDATE
+        assert cs['type'] == 'mixing'
+        assert cs['tank'] == 't0'
+        assert cs['model'] == MIXING_MODEL_2COMP
+        assert cs['value'] == 20.0
+
+        cs = execute_undo(p).operations[0]
+        assert cs['operation'] == API_UPDATE
+        assert cs['type'] == 'mixing'
+        assert cs['tank'] == 't0'
+        assert cs['model'] == MIXING_MODEL_2COMP
+        assert cs['value'] == 10.0
+
+        cs = execute_redo(p).operations[0]
+        assert cs['operation'] == API_UPDATE
+        assert cs['type'] == 'mixing'
+        assert cs['tank'] == 't0'
+        assert cs['model'] == MIXING_MODEL_2COMP
+        assert cs['value'] == 20.0
+
+        cs = delete_mixing(p, ChangeSet({'tank': 't0'})).operations[0]
+        assert cs['operation'] == API_DELETE
+        assert cs['type'] == 'mixing'
+        assert cs['tank'] == 't0'
+
+        cs = execute_undo(p).operations[0]
+        assert cs['operation'] == API_ADD
+        assert cs['type'] == 'mixing'
+        assert cs['tank'] == 't0'
+        assert cs['model'] == MIXING_MODEL_2COMP
+        assert cs['value'] == 20.0
+
+        cs = execute_redo(p).operations[0]
+        assert cs['operation'] == API_DELETE
+        assert cs['type'] == 'mixing'
+        assert cs['tank'] == 't0'
+
+        self.leave(p)
+
+
     # 21 time
 
 
diff --git a/tjnetwork.py b/tjnetwork.py
index 68d71f6..3d6eebd 100644
--- a/tjnetwork.py
+++ b/tjnetwork.py
@@ -57,6 +57,11 @@ SOURCE_TYPE_MASS = api.SOURCE_TYPE_MASS
 SOURCE_TYPE_FLOWPACED = api.SOURCE_TYPE_FLOWPACED
 SOURCE_TYPE_SETPOINT = api.SOURCE_TYPE_SETPOINT
 
+MIXING_MODEL_MIXED = api.MIXING_MODEL_MIXED
+MIXING_MODEL_2COMP = api.MIXING_MODEL_2COMP
+MIXING_MODEL_FIFO = api.MIXING_MODEL_FIFO
+MIXING_MODEL_LIFO = api.MIXING_MODEL_LIFO
+
 TIME_STATISTIC_NONE = api.TIME_STATISTIC_NONE
 TIME_STATISTIC_AVERAGED = api.TIME_STATISTIC_AVERAGED
 TIME_STATISTIC_MINIMUM = api.TIME_STATISTIC_MINIMUM
@@ -542,6 +547,26 @@ def delete_source(name: str, cs: ChangeSet) -> ChangeSet:
     return api.delete_source(name, cs)
 
 
+############################################################
+# mixing 20.[MIXING]
+############################################################
+
+def get_mixing_schema(name: str) -> dict[str, dict[str, Any]]:
+    return api.get_mixing_schema(name)
+
+def get_mixing(name: str, tank: str) -> dict[str, Any]:
+    return api.get_mixing(name, tank)
+
+def set_mixing(name: str, cs: ChangeSet) -> ChangeSet:
+    return api.set_mixing(name, cs)
+
+def add_mixing(name: str, cs: ChangeSet) -> ChangeSet:
+    return api.add_mixing(name, cs)
+
+def delete_mixing(name: str, cs: ChangeSet) -> ChangeSet:
+    return api.delete_mixing(name, cs)
+
+
 ############################################################
 # time 21.[TIMES]
 ############################################################