Tools and Supplies Needed Before You Start
Gather the following before beginning: adjustable wrench or channel-lock pliers, flathead screwdriver, measuring tape, bucket or towel for residual water, and a GFCI outlet within 4 feet of the toilet. Confirm your toilet bowl shape (elongated or round) matches the Bia model purchased. Verify the water shutoff valve behind or below the toilet is operational -- turn it clockwise to test.
Step 1 -- Remove the Existing Toilet Seat
Lift the hinge caps at the rear of the existing toilet seat. Use a flathead screwdriver to hold the bolt nut underneath the bowl rim while turning the top bolt counterclockwise. Lift the seat and hinge plate off. Clean the area around the bolt holes with a damp cloth before proceeding. Note the bolt hole spacing -- standard is 5.5 inches center to center, which the Moen Bia mounting plate accommodates.
Step 2 -- Install the T-Adapter at the Shutoff Valve
Turn the toilet shutoff valve clockwise until water stops. Flush the toilet to clear tank pressure. Place the bucket under the supply line connection at the bottom of the tank. Unscrew the existing supply line from the fill valve shank. Thread the included Moen T-adapter onto the fill valve shank hand tight, then snug with an adjustable wrench -- one quarter turn past hand tight is sufficient. Do not overtighten brass fittings. Reconnect the existing supply hose to the bottom port of the T-adapter. Connect the Moen bidet supply hose (included) to the side port of the T-adapter.
Step 3 -- Mount the Bidet Seat Plate and Attach the Seat
Slide the mounting plate over the toilet bolt holes and insert the bolts through the plate and bowl rim. Thread the provided nuts from underneath and tighten by hand, then snug with a wrench. Do not overtighten -- toilet porcelain cracks under excess torque. Slide the Moen Bia seat onto the mounting plate from the rear until it clicks into the locking position. Tug the seat forward firmly to confirm it is seated -- the seat should not slide.
Step 4 -- First-Use Leak Check and Function Test
Connect the bidet supply hose to the inlet port on the left side of the Bia seat. Open the shutoff valve slowly and inspect all connection points for drips -- T-adapter, supply hose ends, and seat inlet. Plug the Bia power cord into the nearest GFCI outlet. The seat will enter a 30-second startup cycle. After startup, sit on the seat to activate the occupancy sensor and test each function: posterior wash at the lowest pressure setting first, then increase to confirm pressure adjustment, then test seat heat and dryer. Run a nozzle self-clean cycle to verify water flows through and retracts cleanly.