diff --git a/api/s4_tanks.py b/api/s4_tanks.py
index 059566c..f21f66c 100644
--- a/api/s4_tanks.py
+++ b/api/s4_tanks.py
@@ -5,8 +5,8 @@ from .s24_coordinates import *
 import utility
 
 
-OVERFLOW_YES = 'YES'
-OVERFLOW_NO = 'NO'
+OVERFLOW_YES = 'yes'
+OVERFLOW_NO = 'no'
 
 
 def add_tank(name: str, id: str, x: float, y: float, elevation: float, init_level: float = 0, min_level: float = 0, max_level: float = 0, diameter: float = 0, min_vol: float = 0) -> ChangeSet:
diff --git a/script/sql/create/4.tanks.sql b/script/sql/create/4.tanks.sql
index fd5aee4..963f998 100644
--- a/script/sql/create/4.tanks.sql
+++ b/script/sql/create/4.tanks.sql
@@ -1,6 +1,6 @@
 -- [TANKS]
 
-CREATE TYPE TANKS_OVERFLOW AS ENUM ('YES', 'NO');
+CREATE TYPE TANKS_OVERFLOW AS ENUM ('yes', 'no');
 
 CREATE TABLE TANKS
 (