For the last 5 months I've been building a houseboat and am finally to the point where I need to get the blackwater holding tank plumbed. I will be moored 100% of the time with city water hookup, approximately 1 gallon of water per flush, and regular pumpouts (like after every weekend (4-6 people for 3-4 days at a time). The holding tank is 250 gallons and can be drilled any way I want. I would prefer not to use harsh chemicals instead using something like Raritan or Odorlos. my initial plan was to have a 1.5" vent that came out of the top of the tank and up approximately 10' and then turning 90 to the outside.
Will this be enough oxygen for a natural product? Should I add a second vent? If so I would either need to leave the vent about 6" above the holding tank, place it right next to the 1st vent, or have it 90 over then 90 up to run next to the 1st vent.
If you could design the perfect set up what would it be. My next week to work on the boat is March 30-April 10 and the black water tank is #1 on the list.