Originally Posted by Jetexas
Can someone post a photo
of what these vents look like on the exterior of the boat? Now that the mold
smell has subsided, I'm starting to recognize a holding tank smell in my boat. I'm going to attempt a massive cleaning
Someone did. It's up near the top of the page.
If there's a screen in the vent, remove it, it's not needed. Insects build nests in them and if you overfill the tank, sewage will block them. If there's a filter and it's ever gotten wet from overfilling or trying to cleat the vent line with a hose, replace it, or just do away with it and insert a piece of hose in it's place. They are not really needed and often do more harm than good.
If there's a low spot (a loop) in the vent hose, re-route it to eliminate the low spot. The low spot can collect liquids or condensation
and block the vent.
I wouldn't recommend more than about 30 PSI of air pressure if you try to clear a vent hose with air. Also, you need to disconnect the hose from the holding tank or disconnect the inlet from the head
so you don't pressurize the holding tank. Bad things can happen if you do that. They are not designed to be pressurized. If you have an access plate for cleeaning, removing it will relieve the pressure.