When we bought our O'day 35, the hoses were all permeated. That's a nasty smell! Going against popular opinion, I decided to remove the whole works and replace it with a porta pottie. That was two years ago and every now and then, I still get a whiff of that smell, especially when we return to the boat and it has been cooped up for a few days. Perhaps someday I'll go back to a traditional marine head/holding tank, but for now, I like the porta pot. One of the biggest reasons for going this rout came from Peggy, "The Head Mistress". I don't have the exact figures but as I recall, a 5 gallon porta pot is roughly equivalent to a 13 gallon holding tank (which is what we had on board) when you factor in the amount of water that needs to be used in order to push the waste from the bowl, to the tank in order to keep the hoses free of the waste that permeates them. Most people don't use enough water to keep the hoses free and clean because they think they'll fill up the tank too quickly and will have to pump out more often. That may be true, but the waste is now sitting in the hoses and not in the tank where it should be.
My location of the tank was under the v berth and the space is plenty large enough for a larger tank but the opening to get the tank in is narrow so I'd have to cut the opening larger to get it in, more work than I wanted.
Probably more info than you wanted on such a nasty subject, but it's worth considering.
I bought a porta pot that can be plumbed in to have a traditional pumpout but I haven't done that yet. We cruise in more wilderness areas without pumpouts available everywhere so I like the idea of just taking the tank off the boat and unloading it (in the proper manner) without having to find a marina with pumpout facilities.
