Originally Posted by uwe
Our 71 Tradewind ( tank above floor) showed full at 12gal ( tank monitor), but could hold quite a bit more than that. Hence, my estimate of 12-15gal.
Interesting. Our '72 had a ten gallon black tank above the floor, and the '75 has a 15 gallon above the floor. My service manual shows 80 pound black water capacity on above -floor models, and 120 pounds below floor, which at 8#/gallon, works out to about ten gallons and 15 gallons respectively. Of course, the best measure is to start pouring in one gallon jugs of water, till the tank is full, and you will have your answer for your particular coach.