Holding tank vent through hull fitting 2013R29

[LET IT BE]

I suspect I have a blockage in the holding tank vent. And have 4 questions so far!
1 is there a mesh filter in the through hull fitting.
2 if so can it be accessed from outside ( like unscrewing the centre Chrome "cap " )
3 is there a check valve in the vent system to prevent flushing with water from outside
4 what is the make of the trough hull fitting and where are they available

I have tried to flush water through using one of the "ears" that attach to a hose from an outboard flush system and it did not seem to be going in to the tank but spraying out around the edge of the ear. And I did have the pump out cap off.

Any other suggestions before I start pulling out the fridge etc and working from the inside?

 

[Capt’nKarl]

I had a similar issue with the vent on our fresh water tank. First yes, there is a mess filter on the vent tube. When I filled the water tank nothing came out of the vent. Here’s what’s i did. I posted this a couple of weeks ago. I bought regular rubber toilet plunger and took the wooden handle off. On the rubber part I drillled a 1-2 mm hole so it would fit the air compressor fitting. The water tank was empty. I placed a small piece of tissue paper over the fill opening. I put the rubber plunger up against the hull covering the vent opening. I used the air compressor fitting you use to blow away debris and put the end into the rubber plunger and pressed. Within two seconds I heard a slight “pop” and the tissue paper covering the fill opening started to flutter. I then filled the water tank and water came out the vent. Problem solved. I think you could do the same thing with the black water vent.
Capt’nKarl

 

[LET IT BE]

I think I’m going to be taking my “air pig”
And a toilet plunger up to the boat!