As part of shocking the pool, I pulled the light housing out - as it was shorted and had some water in it.
To my surprise the Pentair bulb housing has model numbers "Series" 7885xxx, 7845xxx, and 7895xxx. It says to use with 7821xx, 7822xx, 7823xx, 7906700, 79208900.
The big surprise is - that it says use with fresh water only - and I just converted to a salt system...Arggh. I inherited the pool when I bought the house last year - with little information form the owner.
I'm pretty sure I can find a replacement gasket, and get the unit re-installed.
Does the pool need to be drained to replace the housing with a newer salt friendly model - why does it really matter as long as the ph & alkalinity are maintained?