For the 2007 StarCraft S 18RB, the standard fresh water tank capacity is approximately 31 gallons. The W1192 tank you mentioned measures 10" x 20" x 24" and holds 25 gallons, which is slightly smaller but may fit depending on your RV's available space and mounting setup. We recommend verifying your RV's dimensions before purchasing. Our fresh water tanks are not pre-equipped with filling, drain, or water pump fittings because configurations vary widely. To customize the tank to your needs, we offer a Universal Holding Tank Fittings Kit that includes all necessary fittings and sensors to replicate your original setup. You can view compatible tanks and purchase the fittings kit directly on our website.