The cost--and the issues--involved
It's possible to put a "real" head on just about any boat of any size...it all depends upon how much storage space you're willing to give up, and how much privacy you can do without. Unless it's necessary to create access to space for a holding tank, there shouldn't be any need for any structural work. Parts needed: the toilet, a 3/4" intake thru-hull and seacock, a holding tank, some hose, a vent thru-hull, and deck pumpout fitting. Cost depends upon which toilet, what size holding tank, and whether you do the work yourself, but I'd figure on a minum of $300 for parts alone. 25' is right at the "tipover point" for choosing between a portapotty or a head and holding tank. The "pumpable" portapotties hold 5.5 gallons, and use so little flush water that they offer the equivilant number of flushes to a "real" head and about a 12-15 gallon holding tank... Since the total cost is only a little over $100--vs at least $300--there's nothing to be gained--in fact, you lose capacity--by installing a head and only a 5-6 gallon tank...and since storage space is in such short supply on boats smaller than 25', it really doesn't make much since to fill it up with a tank large enough to give you any appreciable added capacity. It's also important to remember that a "real" head becomes another piece of equipment that has to be maintained...added expense. So our advice is: under 25'...pumpable portapotty. Over 25', head & holding tank...at 25' it depends upon how much you need a "real" head to feel like you own a "real" boat.
