Brass check valves allow fluid flow in one direction only. They prevent the flow of fluid in the other direction. Brass check valves can be used in a wide range of applications to prevent the back flow in systems. Brass is strong and durable, and for many applications it offers a cost-effective alternative to stainless steels. Brass has excellent properties for water, oil, air and fuels etc., but is not resistant to seawater, purified or chlorinated water.