Troubleshooting Groco Type K

[ToddandCelia]

My recently installed Groco Type K was working great...I changed and reseated the deck fitting for the holding tank pumpout. Everything was fine until I pumped out the tank later in the week and now the pump handle seems to have air pushing back against it? After/during pumping out bowl, I am hearing and seeing air bubles in system and bowl and pump handle seems to slowly get pushed down on its own. Should be no clogs and I didn't mess with any other hoses or fittings...

What just happened and what do I need to address? Any leads are appreciated!

[a64pilot]

Two possibilities as I see it, the Joker valve and or the intake valve, Pardon me for not knowing what it's called but a pump must have both an intake and an exhaust valve to function.
I'm going to bet that pumping out the tank put a vacuum on the flapper intake valve and un-seated it, I have the exact same thing on my boat and it started this weekend when I put a new pump unit on the head. I do not have the same brand head, but assume operating principles are the same.

Or you have a clogged vent, vent is easiest to check, I would start there

[RainDog]

Grocco has excellent and friendly support. I would call them. That said, my instinct would be to rebuild the pump. Sounds like the there is air leaking into the pump and breaking the vacuum.

[Ocean Girl]

Vent clogged? Could you by any chance, over filled the tank? Does sound like a vacuum situation, which would point at the tank and it's fitting, vent & outlets. Lord I don't envy you. Relieve the pressure, don't force pump, bad things can happen. Good luck!!