How Plastic Resin Becomes Pipe, Valve, Etc. Get this article in a printer friendly format for reference. S odium hypochlorite possesses some unique qualities that have to be understood if you are going to be able to select a valve for that type of service. Because of their excellent chemical resistance, plastic valves are widely used in sodium hypochlorite applications. But in may cases, the wrong type of valve is put into this service and problems, some potentially dangerous, can develop.
Sodium hypochlorite is inherently an unstable compound.
Two things can happen to it in a piping system that will affect the choice of a valve. Sodium hypochlorite can decompose over time, which results in the formation of crystalline salts, and as it decomposes, one of the decomposition by-products is oxygen gas. Because they are the most common type of plastic valve, True Union Ball Valves are often used in sodium hypochlorite service. When the valve is operated, the ball turns and liquid is trapped in the cavity between the ball and the valve body. The trapped sodium hypochlorite starts to decompose and crystals begin to form.