My filter pumps valves were leaking limiting the vaccum and slowing down filtering. So I dismantled the heads,
The heads are made of dicast material and valves are metal flaps. Both have been painted incuding the valve seats and flaps ???. All four valves
where very leaky.
I removed the corrsion and paint from the valve seats by lightly lapping them. I also retensioned the flaps.
The valves leak much less now so the pump is producing a better vaccum.
This was a free pump slavaged from a autoclave. I would not recommend buying one for filtering unless it was very cheap.