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Have a partner help you slide your new tub into place. Feed the drain shoe into the hole in the floor, and set the rest of the tub down. Make sure the tub is level one more time before securing it to the wall. Make sure the tub is in full contact with the floor so the ledger boards aren’t supporting the full weight. Use screws or nails that are 2–3 in (5.1–7.6 cm) long to secure the tub flange to the the studs. Work slowly so you don’t accidentally crack your tub. Put 1 nail or screw into each stud to keep it in place. Access your pipes from the hole you cut in the room adjacent to your bathtub. Use a pipe wrench to tighten the drain shoe to the P-trap until it’s completely secure. Squeeze a ring of silicone sealant around the pipe and P-trap for another layer of protection from leaks. If the faucet had a screw, put the faucet back on with a screwdriver and turn it clockwise. If the faucet screwed off by itself, twist it back on by hand and use a pipe wrench to secure the faucet in place completely. Let the sealant on your tub dry for 1 day so it’s completely set. Turn the water valve back on and let it fill the tub. Listen for any dripping noises and watch for any noticeable leaks near your drain or on your pipes. If you find any leaks, use more sealant around the leaking area. Check the drain shoe from the access panel you cut earlier so see if any water is leaking underneath your tub. Cut the pieces of drywall to the sizes of your gaps with a reciprocating saw. Hold the piece of drywall or backerboard against the studs so it covers the flange and there’s a 1⁄4 in (0.64 cm) gap between the board and the tub. Use nails to secure the boards in place.  Drywall or backerboard can be purchased from your local hardware store. Don’t forget to install new drywall on the access panel you cut out from the other room. If you’re using tiles, mix tile mortar in a bucket based on the instructions on the packaging. Stir the mortar with a flat trowel and spread it on the drywall. Press the tiles onto the backerboard and hold it in place for 30 seconds. Use tiles that match the existing ones in your bathroom. Otherwise, you’ll have to retile the entire wall. For a fiberglass surround, set the entire piece in place so it covers the tub flange. Drive screws with an electric screwdriver into the divots along the sides and top of the surround so it’s secured to the studs. Once you’ve secured the tiles to the backerboard, place a thin bead of silicone around the bottom of the of the tiles to fill in the gap. Put the tip of the sealant dispenser into the gap, and pull the line slowly so it applies smoothly. Wipe any excess sealant away with your finger.

Summary:
Slide the new tub in place so the flanges rest on the ledger boards. Screw or nail the tub into the studs. Connect the drain shoe to the pipes. Reattach the faucet. Fill the tub and test for leaks the day after it’s installed. Cover the exposed studs and flange with drywall or cement backerboard. Replace the surround. Seal the gap between the tile and tub with silicone sealant.