How To Install A Bathtub | Delta Classic 400
Installing a new bathtub is one of the most impactful upgrades you can make to a bathroom. This complete guide walks through the full installation of the Delta Classic 400 bathtub — from preparing the rough-in to connecting the drain and finishing the surround — so you can get it done right the first time.
Why Choose the Delta Classic 400?
The Delta Classic 400 is a popular alcove bathtub known for its durable acrylic construction, classic styling, and straightforward installation. It's designed with the DIY installer in mind, with a standard 60" x 30" footprint that fits most alcove rough-ins and clear installation instructions from Delta.
Key Features
- 🛁 Standard 60" x 30" alcove fit — compatible with most existing rough-ins
- 💪 Durable acrylic with fiberglass reinforcement
- 🔧 Drain located on left or right end (specify at purchase)
- 🏠 Designed to pair with Delta Classic 400 surround panels
- ✅ Backed by Delta's limited lifetime warranty
What You Will Need
Tools & Materials
- 🛁 Delta Classic 400 bathtub
- 🪵 Mortar bed mix or adjustable bathtub support legs
- 🔩 Drain assembly and overflow plate kit
- 🔧 PVC cement and primer (for drain connections)
- 📏 4-foot level, tape measure, and pencil
- 🔨 Hammer and nails or drill and screws
- 🧴 Silicone caulk and caulk gun
- 🧤 Work gloves and safety glasses
Step-by-Step Installation
Step 1: Prepare the Alcove
Before the tub goes in, confirm that the three walls of the alcove are plumb and the floor is level. Check that the rough drain in the floor aligns with the bathtub's drain location. Install blocking between studs at the tub flange height — this gives you a solid nailing surface to secure the tub.
Step 2: Dry-Fit the Tub
Slide the tub into the alcove without adhesive or mortar to confirm it fits correctly. Check that the drain lines up with the floor drain rough-in and that the tub is level side-to-side and end-to-end. Mark the tub flange position on the studs with a pencil.
Step 3: Set the Mortar Bed
Mix a dry-pack mortar and spread it evenly across the floor of the alcove where the tub will sit. This mortar bed supports the bottom of the tub and prevents flexing and cracking over time. Some installers use adjustable support legs instead — follow the tub manufacturer's recommendation.
Step 4: Set the Tub and Check Level
Carefully lower the tub into the alcove onto the mortar bed. Press it down evenly and immediately check level in all directions. Make any adjustments before the mortar begins to set. Do not stand in the tub during this step.
Step 5: Connect the Drain Assembly
Install the drain body through the tub floor, connecting it to the floor drain rough-in with PVC fittings, cement, and primer. Install the overflow plate and linkage on the end wall of the tub. Test all connections for leaks before closing up the walls.
Step 6: Secure the Tub Flange
Once the mortar has cured and the tub is confirmed level, nail or screw the tub flange to the wall studs through the pre-drilled holes. Do not overtighten — snug is sufficient. The flange holds the top edge of the tub firmly against the wall framing.
Step 7: Install Backer Board and Surround
Install cement backer board or the Delta Classic 400 surround panels over the tub flange and up the walls. Follow the surround installation guide for adhesive application and panel alignment. Keep a 1/8" gap between the bottom of the panels and the tub rim for the caulk joint.
Step 8: Caulk All Seams
Apply a continuous bead of 100% silicone caulk along the joint where the tub meets the walls, and at all panel seams and corners. Smooth the caulk with a wet finger or caulk tool. Allow to cure fully (24–48 hours) before exposing to water.
Pro Installation Tips
Get the Best Results
- 🧹 Clean the alcove floor thoroughly before spreading mortar
- 📐 Double-check level at every step — a tub that isn't level will drain poorly and look off
- 💧 Always pressure-test drain connections before closing up walls
- 🔒 Use 100% silicone caulk (not latex) for the tub-to-wall joint — it's fully waterproof and flexible
- 🏊 Fill the tub with water before caulking — this compresses the tub at its maximum weight, preventing the caulk from pulling away later
- 📅 Wait the full mortar and caulk cure time before first use
Install Your Delta Classic 400 With Confidence
A properly installed bathtub will last for decades with minimal maintenance. Watch the full video for a hands-on walkthrough of every step, helpful close-up shots of the drain and flange connections, and pro tips that make the job go smoothly from start to finish.