I pulled apart one of our heads... about 2 years after we bought the boat... it had been running fine but it had finally clogged and I thought I would do a full job and change the piston ring and yada yada... anyway, I pull out the joker valve.... and its been put in backwards!!!
If you are woindering how they got it in backwards they siliconed it in! backwards!
I dunno how it had worked but we'd never had a problem with it.
Must have been first day at work for some Sunsail maintenance
guy who had lied on his CV