If your Travel Berkey, Big Berkey or Royal Berkey water filtration system water filter is slow to filter water, takes too long to filter water, leaks water between the top and bottom tanks, only filters a little bit of water then stops until the bottom tank is empty or pushes water out of the top of the site glass, this may be the solution to your problem.
The Berkey I use:

The Site Glass accessory on my Berkey: