A double union ball valve is a fitting that can be installed and used to contol the flow of liquid in a pipeline. Double union ball valves are prefered over single union because they make they make it easy to issue repairs and remove the valve for replacement if need be.

A double union ball valve is named after the fact that it has two unions on it – one on both sides. The unions allow the valve to be uninstalled and removed from the pipeline (unscrewed or pulled depending on the join method, socketed or threaded)
This is important because it allows for the pipeline or valve itself to be serviced or checked to see whether it’s blocked; thereafter it can be easily put back on the pipeline. If these design benefits were not in place one would have to cut the piping to remove or service, pipeline or valve alike. Get a double union valve to make future changes easier and more efficient.