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Where the upturned membrane meets the shower curb, I install prefabricated dam corners, available from the membrane manufacturer. I apply two 1/8-inch beads (spaced 1/2 inch apart) of sealant to the pan membrane, then use a trowel to bed the dam corners into the sealant. I try to place all fasteners in the top inch of the upturned edges. If a fastener has to be used below the 1-inch line, I seal it with a small CPE patch bedded in rubber sealant.

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Dam corners (top left) are applied at the curb juncture. Rubber sealant is applied to the pan membrane and the curb framing (top right), the dam corner is pressed into the sealant (bottom left), and the pan membrane is folded tight against the framing and stapled in place (bottom right). With the membrane pan in place, I carefully cut around the bolt heads protruding from the drain, and press the membrane over all four bolts. Finally, I snug down the bolts and cut a hole in the membrane to open the pan to the drain.

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To fit the membrane around the clamping drain, first cut small holes for the flange bolts (top ) and push the membrane over the protruding bolts. Then slice the membrane around the inside diameter of the drain (middle) before bolting the clamp ring in place (bottom).

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Testing the shower pan. I plug the drain with an expansion-type stopper and fill the pan with water up to the top of the curb. Local codes may only require a few hours testing, but I prefer to let the water sit at least overnight. Sunken tubs with whirlpool jets should be tested with all pumps running.