North Dakota Administrative Code
Title 33.1 - Department of Environmental Quality
Article 33.1-14 - NORTH DAKOTA BOILER RULES
Chapter 33.1-14-09 - HEATING, LOW PRESSURE, AND HOT WATER SUPPLY BOILERS -EXISTING INSTALLATIONS
Section 33.1-14-09-10 - Stop valves and check valves

1. If a steam boiler may be closed off from the heating system by closing a steam stop valve, there must be a check valve in the condensate return line between the boiler and the system.

2. If any part of a steam heating system may be closed off from the remainder of the system by closing a steam stop valve, there must be a check valve in the condensate return pipe from that part of the system.

3. If more than one boiler is connected to a system, they must each be equipped with main stops on the discharge and return side, in such a manner not affecting operation of any other boiler.

4. When single boilers are located above the system and can be drained without draining the system, stop valves are optional.