How to Install a Shower Pan and Drain
Step-by-step visual guide to setting a pre-formed acrylic or fiberglass shower base, assembling the drain fitting, and bedding the pan level in mortar.
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🧰 Required Tools & Equipment
- ✓ 4-foot spirit level
- ✓ Tongue-and-groove pliers (Channel locks)
- ✓ Cordless drill with mixing paddle
- ✓ Notched trowel
- ✓ Tape measure
- ✓ Utility knife
📦 Materials & Supplies
- ✓ Shower pan base
- ✓ Shower drain assembly (no-caulk/compression style)
- ✓ Mortar mix or sand/topping mix (50 lb bag)
- ✓ 100% silicone sealant
- ✓ 1-1/4 inch corrosion-resistant screws
- ✓ Plastic sheet / roofing felt
⚠️ Safety Checkpoints & Warnings
- • Wear an N95 respirator and safety glasses while mixing dry mortar mix to avoid silica dust inhalation.
- • Ensure subfloor is completely rigid with zero bounce or deflection before setting base.
- • Verify the drain pipe stub is clean, de-burred, and cut to the exact manufacturer-specified height.
📋 Step-by-Step Guide (6 Steps)
Dry-Fit Base and Check Drain Alignment
Sweep the subfloor clean of all drywall dust, grit, and fasteners. Set the shower pan base flat onto the subfloor to ensure the 2-inch drain pipe penetrates dead-center through the pan hole. Place a 4-foot level across the thresholds and sidewalls to verify the floor is flat, then trace the top flange onto the wall studs.
- • Shower pan sits completely flat against subfloor with drain pipe centered in opening
- • Pencil line visible on studs matching the exact height of the top flange
- • Skipping dry-fit and realizing drain pipe is misaligned after spreading wet mortar
Install Drain Assembly onto Shower Pan
Apply a heavy 3/8-inch continuous bead of 100% silicone sealant under the top lip of the drain body flange. Insert the drain body through the top of the pan drain hole. From the underside of the pan, slide on the rubber gasket followed by the friction washer, then thread the large locknut on by hand and tighten firmly with pliers.
- • Silicone squeezing out uniformly 360 degrees around the drain flange inside the pan
- • Locknut fully seated and tight against underside friction washer
- • Placing rubber gasket on the top side of the shower pan instead of underneath
Lay Moisture Barrier and Mix Mortar Bed
Staple a sheet of roofing felt or plastic sheeting over the subfloor to prevent the wood from drawing moisture out of the mortar. In a 5-gallon bucket, mix mortar with water using a mixing paddle until it reaches a stiff peanut-butter consistency that holds its shape without slumping.
- • Subfloor covered with smooth moisture barrier around drain opening
- • Mortar holds peaked ridges in bucket without running or pooling water
- • Mixing mortar too wet (soupy), which causes it to shrink and lose support under the base
Spread Mortar Bed onto Subfloor
Dump the mixed mortar onto the moisture barrier in mounds 1.5 to 2 inches thick. Use a notched trowel to spread the mortar evenly across the footprint of the base where the pan feet and bottom will contact. Keep the mortar at least 2 inches clear of the drain hole opening so it does not foul the pipe connection.
- • Uniform 1.5-inch to 2-inch thick mortar mounds across the base area
- • Clear 2-inch margin around PVC drain pipe stub
- • Spreading mortar right up against the drain pipe, preventing rubber compression seal installation
Set Base and Level in All Directions
Lower the shower pan onto the wet mortar bed, guiding the drain body over the drain pipe. Step into the pan wearing clean shoes and shift your weight gently to bed the pan ribs into the mortar until the perimeter flange hits your pencil marks. Check your level across the front threshold, back wall, and both side rims.
- • Level bubble centered on all four rim edges of the base
- • Base perimeter flange rests firmly against subfloor/stud pencil reference marks
- • Checking level inside the sloped pan basin rather than on the flat perimeter thresholds
Fasten Flange and Connect Compression Drain
Pre-drill pilot holes through the shower pan mounting flange into each wall stud, then drive corrosion-resistant screws through the flange until snug (do not over-tighten). Slide the rubber compression donut gasket down around the 2-inch PVC pipe into the drain body, followed by the threaded brass/plastic locking ring. Tighten the ring securely with the provided tool or pliers, then snap on the strainer grate.
- • Screw heads flush against mounting flange without cracking the acrylic lip
- • Compression rubber gasket fully driven and compressed around pipe inside drain body
- • Strainer grate snapped flush into drain opening
- • Driving screws directly through flange without pilot holes, causing the acrylic flange to crack
Credit: inspired by an original tutorial by The Excellent Laborer — watch the original on YouTube.
Don’t have everything?
- No Drill mixing paddle? Hand mixing trowel in a shallow tub or wheelbarrow
- No 4-foot spirit level? 2-foot spirit level placed on a straight 2x4 board