How to Install a New Bathtub or Shower Plumbing
Installing a new bathtub or shower is one of the most valuable upgrades you can make in a home renovation. Whether you are completing a full bathroom remodel or simply replacing an old unit, proper plumbing installation ensures long lasting performance, leak free operation, and safe water flow. While some parts of bathtub and shower installation can be handled by confident DIYers, the plumbing components require skill, precision, and a solid understanding of building codes.
This guide walks you through the full process of installing plumbing for a new bathtub or shower. We cover preparation, rough in plumbing, drain and supply line installation, venting, water testing, fixture setup, and final inspections. You will also learn when it is wise to bring in licensed plumbers such as the experts at Advanced Heat, AC, & Plumbing for professional installation and peace of mind.
Understanding the Plumbing Requirements for a Tub or Shower
Before installing a bathtub or shower, you must understand what plumbing components are involved. These systems require correctly placed drain lines, hot and cold supply lines, venting, and waterproofing. Mistakes in any of these areas can lead to leaks, mold growth, weak water pressure, or slow draining.
Key plumbing components include
- Water supply lines
- Drain and overflow assembly
- P trap
- Main drain line
- Vent pipe
- Shower valve or tub filler
- Pressure balancing valve
- Shutoff valves
The complexity of the project depends on whether you are replacing a unit in the same location or moving the plumbing to a new spot. If you are relocating pipes, professional support is strongly recommended, and a consultation through licensed plumbing services helps you understand the structural and code implications.
Step 1: Prepare the Bathroom for Installation
Preparation is critical for a safe and efficient bathtub or shower installation.
Shut off the water
Turn off the water supply at the main line or the bathroom’s shutoff valves.
Remove the old tub or shower
Carefully dismantle the old unit by removing the faucet trim, drain, and wall surround. Cut away any old caulking and detach the drain assembly. If the unit is large, you may need to cut it into smaller pieces.
Inspect the framing
Once the unit is removed, inspect the studs and subfloor for signs of rot, mold, or water damage. Repair any structural issues before installing new plumbing.
Measure the space
Accurate measurements ensure your new bathtub or shower pan fits properly. Check the width, depth, and drain location.
Step 2: Install or Adjust the Drain Assembly
The drain assembly is one of the most important components of tub or shower plumbing.
Components of the drain assembly
- P trap
- Drainpipe
- Overflow pipe (for bathtubs)
- Gaskets
- Seals
- Drain flange
Setting the drain location
If the tub or shower is remaining in the same place, simply connect the new drain to the existing P trap. If the location is changing, the P trap and drainpipe must be relocated.
This may require cutting into the floor or adjusting joists. Work like this should be handled by trained plumbers who understand slope requirements and safety codes.
Establishing proper drain slope
Drain pipes must slope at least one quarter inch per foot to ensure proper flow. Incorrect slope leads to standing water, odors, and clogs.
Because correct slope is essential, homeowners often rely on trained specialists from Advanced Heat, AC, & Plumbing’s plumbing repair team when major drain adjustments are needed.
Step 3: Install Water Supply Lines
The next step is connecting the hot and cold water lines to the new bathtub or shower valve.
Modern supply line options
- Copper
- PEX
- CPVC
PEX is popular because it is flexible and easy to run through framing, while copper remains a durable long term material.
Steps for supply line installation
- Run hot and cold lines from the nearest manifold or junction.
- Connect the lines to the mixing valve or tub filler body.
- Secure the pipes firmly to prevent movement.
- Ensure anti scald or pressure balancing valves are installed to protect against temperature fluctuations.
If your remodel includes new water filtration or pressure adjustments, a system evaluation through water analysis and filtration services may be valuable.
Step 4: Install the Shower Valve or Tub Filler
The shower valve controls water flow, temperature, and pressure. Accurate installation ensures safe and comfortable bathing.
Proper valve placement
- Standard height for shower valves: 38 to 48 inches from the floor
- Standard tub filler height: 4 to 6 inches above the tub rim
Types of valves
- Single handle valves
- Pressure balancing valves
- Thermostatic valves
- Diverter valves (for tub/shower combos)
Ensure all valve connections are tightened and sealed appropriately. A leak behind the wall can cause costly damage if unnoticed.
Step 5: Install the Bathtub or Shower Pan
Once the plumbing is set, the tub or shower pan can be installed.
Installation steps
- Dry fit the tub or pan to confirm drain alignment.
- Apply mortar or support bed if required by the manufacturer.
- Level the unit using shims.
- Attach the drain assembly from below or through access panels.
- Screw the tub flange or shower pan into studs.
Proper leveling prevents cracking, leaking, or shifting over time.
Step 6: Connect the Overflow and Drain (for Bathtubs)
If you are installing a bathtub, the overflow drain must be connected before final placement.
Overflow installation tips
- Use the manufacturer’s gaskets to prevent leaks
- Tighten screws carefully, avoiding overtightening
- Ensure overflow tube lines up perfectly with the tub wall
Once installed, connect the overflow pipe to the main drain assembly.
Step 7: Install the Shower Head and Tub Spout
After the walls are prepared, install the final fixtures.
Shower heads
Connect the shower arm to the drop ear elbow anchored inside the wall. Use thread tape to seal the threads.
Tub spouts
Tub spouts attach via slip fit or threaded connections. Ensure the proper spout type is used for your pipe setup.
Step 8: Test the Plumbing System
Before closing walls or installing tile, the plumbing must be tested.
Perform these tests
- Check all connections for leaks
- Test hot and cold water balance
- Run the shower and tub to confirm drainage
- Inspect water pressure
- Perform a tub fill test to check the overflow
If issues arise, a technician trained in full HVAC and plumbing diagnostics can identify and correct them.
Step 9: Waterproof the Shower or Tub Surround
Proper waterproofing is critical to prevent mold, rot, and water damage.
Waterproofing essentials
- Use cement board instead of drywall in wet areas
- Apply waterproof membrane over the walls
- Seal seams, corners, and gaps
- Use high quality caulk around fixtures and corners
Skipping this step can lead to expensive repairs later.
Step 10: Install Tile or Wall Panels
Once waterproofing is complete, install the shower walls, tile, or tub surround. Make sure all plumbing fixtures emerge cleanly from the finished surface.
Step 11: Complete Final Fixture Installation
After tile or wall panels are installed, add the finishing touches.
Final fixtures
- Shower trim kit
- Tub spout escutcheon
- Shower arm flange
- Faucet handles
- Handheld shower brackets
These components complete the look and functionality of your new tub or shower area.
When to Call a Professional Plumber
Installing tub or shower plumbing requires careful planning, knowledge of building codes, and precise workmanship. You should call professionals if:
- You are relocating a tub or shower to a new location
- Your home has old or deteriorated pipes
- You need to cut into load bearing walls or floors
- Your bathroom has poor water pressure or drainage
- You are unsure about venting or slope requirements
- You want guaranteed leak free installation
Expert installation ensures long lasting performance and protects your home from water damage. Commercial scale remodels benefit from skilled specialists through professional plumbing support for larger projects.
FAQs About Installing Bathtub and Shower Plumbing
1. Can I install tub or shower plumbing myself?
Some skilled DIYers can handle basic replacements, but moving plumbing or working behind walls is best left to licensed professionals.
2. How long does installation take?
Replacing a unit in the same spot takes one to two days. Moving plumbing may take several days.
3. Do I need a permit to install a new tub or shower?
Yes. Plumbing work almost always requires permits and inspections.
4. Should I upgrade pipes during installation?
If pipes are old, corroded, or undersized, upgrading them during the remodel is strongly recommended.
5. How do I know if the plumbing is installed correctly?
It should pass both leak tests and a final inspection by a licensed professional.
Conclusion
Installing plumbing for a new bathtub or shower is a complex but rewarding part of a bathroom renovation. From preparing the space and setting the drain assembly to running supply lines and waterproofing the walls, every step must be completed with precision. When done correctly, your new bathroom will offer years of comfort, functionality, and reliability.
For safe, professional installation that meets code and protects your home, trust the licensed experts at Advanced Heat, AC, & Plumbing. Their experienced team can help you with everything from basic fixture replacements to complete plumbing relocations, ensuring your renovation is built on a strong and dependable foundation.
