Raritan offers over 200 sizes and shapes of only the best quality, extra thick-walled, 3/8” (.9cm) minimum thickness, seamless polyethylene holding and water tanks. Polyethylene is the only choice for sewage holding tanks because urine is highly corrosive. Polyethylene tanks won’t corrode, leak, shrink, bulge or crack under the weight of sewage and also won’t permeate with sewage odor. Installation diagrams have not been included because “one size fits all” installations don’t fit all boats. Raritan will help you select the best tank location for your boat, the right size tank, and the best way to install it. Then we will expedite your tank order. All fittings are installed at the factory when your tank is made, in the locations, number and sizes you need—eliminating the need for “fitting relocation kits”.