Our watermaker has over 3,500 hours since new in 2000. We love it. Although it was still working last week the CAT pump  had started to leak and needs servicing .  ( One of the longest jobs ever to take the pump out )

The pump is now with CAT pump agents in the UK.  They mention that on stripping the pump down 

" it has been de-rated as two of the plungers have been blanked off leaving only one remaining "

I know nothing about CAT pumps---does this discovery make sense?   

I have asked the same question of Dessalator but I thought I might get a quicker answer from this email, plus maybe adding to the general knowledge of other owners.

Ian and Judy, Pen Azen, SM 302, Kilada, Greece