diff --git a/api/__init__.py b/api/__init__.py
index 9a3d849..22fa887 100644
--- a/api/__init__.py
+++ b/api/__init__.py
@@ -48,6 +48,7 @@ from .s10_status import get_status_schema, get_status, set_status
 
 from .s11_patterns import get_pattern_schema, get_pattern, set_pattern, add_pattern, delete_pattern
 
+from .s12_curves import CURVE_TYPE_PUMP, CURVE_TYPE_EFFICIENCY, CURVE_TYPE_VOLUME, CURVE_TYPE_HEADLOSS
 from .s12_curves import get_curve_schema, get_curve, set_curve, add_curve, delete_curve
 
 from .s13_controls import get_control_schema, get_control, set_control
diff --git a/api/s12_curves.py b/api/s12_curves.py
index 14bc2ba..d20f1ec 100644
--- a/api/s12_curves.py
+++ b/api/s12_curves.py
@@ -1,34 +1,81 @@
 from .operation import *
 
+CURVE_TYPE_PUMP = 'PUMP'
+CURVE_TYPE_EFFICIENCY = 'EFFICIENCY'
+CURVE_TYPE_VOLUME = 'VOLUME'
+CURVE_TYPE_HEADLOSS = 'HEADLOSS'
 
 def get_curve_schema(name: str) -> dict[str, dict[str, Any]]:
     return { 'id'     : {'type': 'str'  , 'optional': False , 'readonly': True },
+             'c_type' : {'type': 'str'  , 'optional': False , 'readonly': False},
              'coords' : {'type': 'list' , 'optional': False , 'readonly': False, 
                            'element': { 'x'  : {'type': 'float' , 'optional': False , 'readonly': False }, 
                                         'y'  : {'type': 'float' , 'optional': False , 'readonly': False } }}}
 
 
 def get_curve(name: str, id: str) -> dict[str, Any]:
+    c_one = read(name, f"select * from _curve where id = '{id}'")
     cus = read_all(name, f"select * from curves where id = '{id}' order by _order")
     cs = []
     for r in cus:
         cs.append({ 'x': float(r['x']), 'y': float(r['y']) })
-    return { 'id': id, 'coords': cs }
+    d = {}
+    d['id'] = id
+    d['c_type'] = c_one['type']
+    d['coords'] = cs
+    return d
 
 
 def set_curve_cache(name: str, cs: ChangeSet) -> SqlChangeSet:
     id = cs.operations[0]['id']
+    f_id = f"'{id}'"
 
     old = get_curve(name, id)
-    new = { 'id': id, 'coords': [] }
+    old_f_type = f"'{old['c_type']}'"
 
-    f_id = f"'{id}'"
+    new = { 'id': id }
+    if 'coords' in cs.operations[0]:
+        new['coords'] = cs.operations[0]['coords']
+    else:
+        new['coords'] = old['coords']
+    if 'c_type' in cs.operations[0]:
+        new['c_type'] = cs.operations[0]['c_type']
+    else:
+        new['c_type'] = old['c_type']
+    new_f_type = f"'{new['c_type']}'"
 
     # TODO: transaction ?
     redo_sql = f"delete from curves where id = {f_id};"
-    redo_sql += f"\ndelete from _curve where id = {f_id};"
-    if len(cs.operations[0]['coords']) > 0:
-        redo_sql += f"\ninsert into _curve (id) values ({f_id});"
+    redo_sql += f"\nupdate _curve set type = {new_f_type} where id = {f_id};"
+    for xy in new['coords']:
+        f_x, f_y = xy['x'], xy['y']
+        redo_sql += f"\ninsert into curves (id, x, y) values ({f_id}, {f_x}, {f_y});"
+
+    undo_sql = f"delete from curves where id = {f_id};"
+    undo_sql += f"\nupdate _curve set type = {old_f_type} where id = {f_id};"
+    for xy in old['coords']:
+        f_x, f_y = xy['x'], xy['y']
+        undo_sql += f"\ninsert into curves (id, x, y) values ({f_id}, {f_x}, {f_y});"
+
+    redo_cs = g_update_prefix | { 'type': 'curve' } | new
+    undo_cs = g_update_prefix | { 'type': 'curve' } | old
+
+    return SqlChangeSet(redo_sql, undo_sql, redo_cs, undo_cs)
+
+
+def set_curve(name: str, cs: ChangeSet) -> ChangeSet:
+    return execute_command(name, set_curve_cache(name, cs))
+
+
+def add_curve_cache(name: str, cs: ChangeSet) -> SqlChangeSet:
+    id = cs.operations[0]['id']
+    f_id = f"'{id}'"
+
+    new = { 'id': id, 'c_type': cs.operations[0]['c_type'], 'coords': [] }
+    new_f_type = f"'{new['c_type']}'"
+
+    # TODO: transaction ?
+    redo_sql = f"\ninsert into _curve (id, type) values ({f_id}, {new_f_type});"
     for xy in cs.operations[0]['coords']:
         x, y = float(xy['x']), float(xy['y'])
         f_x, f_y = x, y
@@ -37,35 +84,38 @@ def set_curve_cache(name: str, cs: ChangeSet) -> SqlChangeSet:
 
     undo_sql = f"delete from curves where id = {f_id};"
     undo_sql += f"\ndelete from _curve where id = {f_id};"
-    if len(old['coords']) > 0:
-        undo_sql += f"\ninsert into _curve (id) values ({f_id});"
-    for xy in old['coords']:
-        f_x, f_y = xy['x'], xy['y']
-        undo_sql += f"\ninsert into curves (id, x, y) values ({f_id}, {f_x}, {f_y});"
 
-    redo_cs = { 'type': 'curve' } | new
-    undo_cs = { 'type': 'curve' } | old
+    redo_cs = g_add_prefix | { 'type': 'curve' } | new
+    undo_cs = g_delete_prefix | { 'type': 'curve' } | { 'id' : id }
 
     return SqlChangeSet(redo_sql, undo_sql, redo_cs, undo_cs)
 
 
-def set_curve(name: str, cs: ChangeSet) -> ChangeSet:
-    result = set_curve_cache(name, cs)
-    result.redo_cs |= g_update_prefix
-    result.undo_cs |= g_update_prefix
-    return execute_command(name, result)
-
-
 def add_curve(name: str, cs: ChangeSet) -> ChangeSet:
-    result = set_curve_cache(name, cs)
-    result.redo_cs |= g_add_prefix
-    result.undo_cs |= g_delete_prefix
-    return execute_command(name, result)
+    return execute_command(name, add_curve_cache(name, cs))
+
+
+def delete_curve_cache(name: str, cs: ChangeSet) -> SqlChangeSet:
+    id = cs.operations[0]['id']
+    f_id = f"'{id}'"
+
+    old = get_curve(name, id)
+    old_f_type = f"'{old['c_type']}'"
+
+    redo_sql = f"delete from curves where id = {f_id};"
+    redo_sql += f"\ndelete from _curve where id = {f_id};"
+
+    # TODO: transaction ?
+    undo_sql = f"\ninsert into _curve (id, type) values ({f_id}, {old_f_type});"
+    for xy in old['coords']:
+        f_x, f_y = xy['x'], xy['y']
+        undo_sql += f"\ninsert into curves (id, x, y) values ({f_id}, {f_x}, {f_y});"
+
+    redo_cs = g_delete_prefix | { 'type': 'curve' } | { 'id' : id }
+    undo_cs = g_add_prefix | { 'type': 'curve' } | old
+
+    return SqlChangeSet(redo_sql, undo_sql, redo_cs, undo_cs)
 
 
 def delete_curve(name: str, cs: ChangeSet) -> ChangeSet:
-    cs.operations[0]['coords'] = []
-    result = set_curve_cache(name, cs)
-    result.redo_cs |= g_delete_prefix
-    result.undo_cs |= g_add_prefix
-    return execute_command(name, result)
+    return execute_command(name, delete_curve_cache(name, cs))
diff --git a/script/sql/create/0.base.sql b/script/sql/create/0.base.sql
index 0d508f0..255d95b 100644
--- a/script/sql/create/0.base.sql
+++ b/script/sql/create/0.base.sql
@@ -2,6 +2,8 @@ create type _node_type as enum ('junction', 'reservoir', 'tank');
 
 create type _link_type as enum ('pipe', 'pump', 'valve');
 
+create type _curve_type as enum ('PUMP', 'EFFICIENCY', 'VOLUME', 'HEADLOSS');
+
 create table _node
 (
   id varchar(32) primary key
@@ -17,6 +19,7 @@ create table _link
 create table _curve
 (
   id varchar(32) primary key
+, type _curve_type not null
 );
 
 create table _pattern
diff --git a/script/sql/drop/0.base.sql b/script/sql/drop/0.base.sql
index adf7030..e76a8ad 100644
--- a/script/sql/drop/0.base.sql
+++ b/script/sql/drop/0.base.sql
@@ -6,6 +6,8 @@ drop table if exists _link;
 
 drop table if exists _node;
 
+drop type if exists _curve_type;
+
 drop type if exists _link_type;
 
 drop type if exists _node_type;
diff --git a/test_tjnetwork.py b/test_tjnetwork.py
index bc84873..4254d5c 100644
--- a/test_tjnetwork.py
+++ b/test_tjnetwork.py
@@ -1648,15 +1648,25 @@ class TestApi:
         self.enter(p)
 
         assert is_curve(p, 'c0') == False
-        c0 = get_curve(p, 'c0')
-        assert c0['id'] == 'c0'
-        assert c0['coords'] == []
 
-        set_curve(p, ChangeSet({'id' : 'c0', 'coords': [{'x': 1.0, 'y': 2.0}, {'x': 2.0, 'y': 1.0}]}))
+        add_curve(p, ChangeSet({'id' : 'c0', 'c_type' : CURVE_TYPE_PUMP, 'coords': [{'x': 1.0, 'y': 2.0}, {'x': 2.0, 'y': 1.0}]}))
 
         assert is_curve(p, 'c0')
         c0 = get_curve(p, 'c0')
         assert c0['id'] == 'c0'
+        assert c0['c_type'] == CURVE_TYPE_PUMP
+        xys = c0['coords']
+        assert len(xys) == 2
+        assert xys[0]['x'] == 1.0
+        assert xys[0]['y'] == 2.0
+        assert xys[1]['x'] == 2.0
+        assert xys[1]['y'] == 1.0
+
+        set_curve(p, ChangeSet({'id' : 'c0', 'c_type': CURVE_TYPE_EFFICIENCY}))
+
+        c0 = get_curve(p, 'c0')
+        assert c0['id'] == 'c0'
+        assert c0['c_type'] == CURVE_TYPE_EFFICIENCY
         xys = c0['coords']
         assert len(xys) == 2
         assert xys[0]['x'] == 1.0
@@ -1666,11 +1676,15 @@ class TestApi:
 
         set_curve(p, ChangeSet({'id' : 'c0', 'coords': []}))
 
-        assert is_curve(p, 'c0') == False
         c0 = get_curve(p, 'c0')
         assert c0['id'] == 'c0'
+        assert c0['c_type'] == CURVE_TYPE_EFFICIENCY
         assert c0['coords'] == []
 
+        delete_curve(p, ChangeSet({'id' : 'c0'}))
+
+        assert is_curve(p, 'c0') == False
+
         self.leave(p)
 
 
@@ -1678,10 +1692,40 @@ class TestApi:
         p = 'test_curve_op'
         self.enter(p)
 
-        cs = set_curve(p, ChangeSet({'id' : 'c0', 'coords': [{'x': 1.0, 'y': 2.0}, {'x': 2.0, 'y': 1.0}]})).operations[0]
+        cs = add_curve(p, ChangeSet({'id' : 'c0', 'c_type' : CURVE_TYPE_PUMP, 'coords': [{'x': 1.0, 'y': 2.0}, {'x': 2.0, 'y': 1.0}]})).operations[0]
+        assert cs['operation'] == API_ADD
+        assert cs['type'] == CURVE
+        assert cs['id'] == 'c0'
+        assert cs['c_type'] == CURVE_TYPE_PUMP
+        xys = cs['coords']
+        assert len(xys) == 2
+        assert xys[0]['x'] == 1.0
+        assert xys[0]['y'] == 2.0
+        assert xys[1]['x'] == 2.0
+        assert xys[1]['y'] == 1.0
+
+        cs = execute_undo(p).operations[0]
+        assert cs['operation'] == API_DELETE
+        assert cs['type'] == CURVE
+        assert cs['id'] == 'c0'
+
+        cs = execute_redo(p).operations[0]
+        assert cs['operation'] == API_ADD
+        assert cs['type'] == CURVE
+        assert cs['id'] == 'c0'
+        assert cs['c_type'] == CURVE_TYPE_PUMP
+        xys = cs['coords']
+        assert len(xys) == 2
+        assert xys[0]['x'] == 1.0
+        assert xys[0]['y'] == 2.0
+        assert xys[1]['x'] == 2.0
+        assert xys[1]['y'] == 1.0
+
+        cs = set_curve(p, ChangeSet({'id' : 'c0', 'c_type': CURVE_TYPE_EFFICIENCY})).operations[0]
         assert cs['operation'] == API_UPDATE
         assert cs['type'] == CURVE
         assert cs['id'] == 'c0'
+        assert cs['c_type'] == CURVE_TYPE_EFFICIENCY
         xys = cs['coords']
         assert len(xys) == 2
         assert xys[0]['x'] == 1.0
@@ -1693,12 +1737,7 @@ class TestApi:
         assert cs['operation'] == API_UPDATE
         assert cs['type'] == CURVE
         assert cs['id'] == 'c0'
-        assert cs['coords'] == []
-
-        cs = execute_redo(p).operations[0]
-        assert cs['operation'] == API_UPDATE
-        assert cs['type'] == CURVE
-        assert cs['id'] == 'c0'
+        assert cs['c_type'] == CURVE_TYPE_PUMP
         xys = cs['coords']
         assert len(xys) == 2
         assert xys[0]['x'] == 1.0
@@ -1706,6 +1745,44 @@ class TestApi:
         assert xys[1]['x'] == 2.0
         assert xys[1]['y'] == 1.0
 
+        cs = execute_redo(p).operations[0]
+        assert cs['operation'] == API_UPDATE
+        assert cs['type'] == CURVE
+        assert cs['id'] == 'c0'
+        assert cs['c_type'] == CURVE_TYPE_EFFICIENCY
+        xys = cs['coords']
+        assert len(xys) == 2
+        assert xys[0]['x'] == 1.0
+        assert xys[0]['y'] == 2.0
+        assert xys[1]['x'] == 2.0
+        assert xys[1]['y'] == 1.0
+
+        cs = set_curve(p, ChangeSet({'id' : 'c0', 'coords': []})).operations[0]
+        assert cs['operation'] == API_UPDATE
+        assert cs['type'] == CURVE
+        assert cs['id'] == 'c0'
+        assert cs['c_type'] == CURVE_TYPE_EFFICIENCY
+        assert cs['coords'] == []
+
+        cs = execute_undo(p).operations[0]
+        assert cs['operation'] == API_UPDATE
+        assert cs['type'] == CURVE
+        assert cs['id'] == 'c0'
+        assert cs['c_type'] == CURVE_TYPE_EFFICIENCY
+        xys = cs['coords']
+        assert len(xys) == 2
+        assert xys[0]['x'] == 1.0
+        assert xys[0]['y'] == 2.0
+        assert xys[1]['x'] == 2.0
+        assert xys[1]['y'] == 1.0
+
+        cs = execute_redo(p).operations[0]
+        assert cs['operation'] == API_UPDATE
+        assert cs['type'] == CURVE
+        assert cs['id'] == 'c0'
+        assert cs['c_type'] == CURVE_TYPE_EFFICIENCY
+        assert cs['coords'] == []
+
         self.leave(p)
 
 
@@ -1993,7 +2070,7 @@ class TestApi:
         assert ge['pattern'] == 'pa0'
         assert ge['effic'] == None
 
-        set_curve(p, ChangeSet({'id' : 'c0', 'coords': [{'x': 1.0, 'y': 2.0}, {'x': 2.0, 'y': 1.0}]}))
+        add_curve(p, ChangeSet({'id' : 'c0', 'c_type' : CURVE_TYPE_PUMP, 'coords': [{'x': 1.0, 'y': 2.0}, {'x': 2.0, 'y': 1.0}]}))
         set_pump_energy(p, ChangeSet({'pump' : 'p0', 'effic': 'c0'}))
         ge = get_pump_energy(p, 'p0')
         assert ge['pump'] == 'p0'
@@ -2012,7 +2089,7 @@ class TestApi:
         add_junction(p, ChangeSet({'id': 'j2', 'x': 0.0, 'y': 10.0, 'elevation': 20.0}))
         add_pump(p, ChangeSet({'id': 'p0', 'node1': 'j1', 'node2': 'j2', 'power': 0.0}))
         add_pattern(p, ChangeSet({'id' : 'pa0', 'factors': [1.0, 2.0, 3.0]}))
-        set_curve(p, ChangeSet({'id' : 'c0', 'coords': [{'x': 1.0, 'y': 2.0}, {'x': 2.0, 'y': 1.0}]}))
+        add_curve(p, ChangeSet({'id' : 'c0', 'c_type' : CURVE_TYPE_PUMP, 'coords': [{'x': 1.0, 'y': 2.0}, {'x': 2.0, 'y': 1.0}]}))
 
         cs = set_pump_energy(p, ChangeSet({'pump' : 'p0'})).operations[0]
         assert cs['operation'] == API_UPDATE
diff --git a/tjnetwork.py b/tjnetwork.py
index 0d9a391..9a560cd 100644
--- a/tjnetwork.py
+++ b/tjnetwork.py
@@ -47,6 +47,11 @@ LINK_STATUS_OPEN = api.LINK_STATUS_OPEN
 LINK_STATUS_CLOSED = api.LINK_STATUS_CLOSED
 LINK_STATUS_ACTIVE = api.LINK_STATUS_ACTIVE
 
+CURVE_TYPE_PUMP = api.CURVE_TYPE_PUMP
+CURVE_TYPE_EFFICIENCY = api.CURVE_TYPE_EFFICIENCY
+CURVE_TYPE_VOLUME = api.CURVE_TYPE_VOLUME
+CURVE_TYPE_HEADLOSS = api.CURVE_TYPE_HEADLOSS
+
 TIME_STATISTIC_NONE = api.TIME_STATISTIC_NONE
 TIME_STATISTIC_AVERAGED = api.TIME_STATISTIC_AVERAGED
 TIME_STATISTIC_MINIMUM = api.TIME_STATISTIC_MINIMUM