What makes the Cat 310 pump heads wash out? Has anyone ever figured out why they do that?
Here's my theory: The head washout (manifold) falls into a few categories of general chemical erosion, cavitation and age. The chemical erosion is obviously due to chemical and will take out any brass headed pump. The cavitation issue can be from bad plumbing, hot water and bad pump design. The bad pump design goes to the use of a valve common to many models and as one old man once told me, 'something that is good for everything is good for nothing'.
The washout in the valve area is common is the result of too much restriction and too small surface area for the o-ring seal. The ID of a CAT valve is very small compared to other brands, like Arimitsu (the best in this regard). This small opening will increase the water velocity and cause the pumps to cavitate easier. Cavitation destroys pump heads. Also, the thin o-ring concentrates the vacuum and pressure over a small area, and thereby, does not leave much material to seal against, or erode away before the seal is gone.
These are my thoughts.