The female threads on our valves, follow the same specification as those on all our fittings, by using a BSP parallel thread.
A female BSP parallel thread will accommodate either a male parallel BSP thread ora male tapered BSP thread.
Threaded double union valves are far more flexible than threaded valves without unions. The union allows the valve end to be turned and so facilitates the winding on, or off of the threaded fitting.