A customer with really nasty well water was asking my help on thier Berkey Filters. I had never experienced water like this so swapped filters with them so that I could examine these. The surface was coated with muddy rust. The middle photo is after being sprayed at an angle with a garden hose. At that point the filter was going to work pretty well, but I then used a new "Scotch Bright" pad and carefully scrubbed it and got what oyu see in photo #3.

Some advise on using the Scotch Brite pad. Use it under running water, Use a new one. If you have used it for other things you might be adding oil to the surface of your filter. The amount of pressure to use I would call light but firm. Start very light and increase slightly if needed. I held it by the base, then held the pad in my other hand and rotated the filter while moving up and down to give the surface plenty of running water to flush away the junk rather then be pressing it back into the filter.

When oyu are satidfied with how clean the filter is re-prime the filter. This will push out any tiny debris you may have pressed into some of the pores.

My advise is to only clean when flow has slowed to the point of it being a problem. On relatively clean water a pair of filter is expected to run more then 6000 gallons on a single set. If nasty water like the customer above no doubt a lot less. what you see was from less then 100 gallons. I am hoping this customer will keep track and keep in touch as this is a great case study of these systems and bad water.