Sewage treatment is the responsibility of  all boaters, please take this seriously.  One gallon on untreated waste can pollute as much as 10,000 gallons of treated waste.  Even small  amounts of untreated waste creates a real strain on the BOD (biological oxygen demand) in the environment, not to mention the bacterial problems.

Be responsible!  You have three options:

Option 1:
Pump out the holding tanks each time you get gas or when they are full. "Big Dog"  presently has two holding tanks which can be pumped out at most gas stations on the water.  Onboard tanks will hold about 100 flushes before needing a  pumpout.  Professional pumpout  is the best, cheapest, and most environmentally friendly way to get rid of your waste.   On many lakes and reservoirs, this is your ONLY option.

Option 2:
If you dock has a sewer hook up,  or if your dock has bathrooms, then you can pump your own boat into a rolling waste caddy, then wheel it over to the toilet and dispose of your waste into the municipal sewage system (i.e. the flush toilets on your dock).   The rolling tank along with the pumping mechanism is about $400.  Here is one place to get it:

                       Waste Caddy

Option 3:
Unless you are located in an EPA zero discharge zone, then you can treat your waste with a type-1 EPA approved sewage treatment system.  Once your waste has been treated then it can be discharged.  This system will connect to the existing toilet and is compatible with the existing onboard plumbing.  It costs from $600 to $900 and is suitable for fresh or saltwater.  Here's one place to get it:

                      Lectra/San and Opti/San waste treatment systems