PEX or copper in the shower wall
Both materials are widely used when installed to the manufacturer's instructions. The choice comes down to the house and the job.
PEX
- Flexible, so fewer fittings behind the wall
- Resists bursting from a single freeze better than rigid pipe
- Faster to install in tight remodels
- Must be protected from sunlight and sharp edges
Copper
- Long track record in older homes
- Rigid, so it needs more fittings and soldering
- Handles heat and sunlight well
- Pairs naturally with existing copper
If your house already has copper and you are only moving the shower valve, a good plumber can transition to PEX with approved fittings. If the whole run is old galvanized steel, the conversation is about repiping, not just the shower.
Shower valve types at a glance
| Valve type | What it does | Best for |
|---|---|---|
| Pressure-balancing | Keeps temperature steady when a toilet flushes | Most single-handle showers |
| Thermostatic | Holds a set temperature and splits flow | Multi-head and body-spray showers |
| Diverter | Sends water to tub spout or shower head | Tub and shower combinations |
| Transfer or volume-control | Runs several outlets separately | Larger custom showers |
Pick the valve before you pick trim. The rough-in valve sits in the wall, and the trim only covers it.
How a shower plumbing rebuild runs
- 1
Open the wall and plan the layout
Studs get framed for the valve, with a blocked backer for the shower arm.
- 2
Rough in the supply and the drain
The plumber sets the valve at the right depth for your tile, runs PEX or copper, and ties in the drain.
- 3
Pressure test
The supply lines are tested with air or water, then watched for a drop. Do not skip this.
- 4
Rough-in inspection
The inspector sees the pipes before the wall is closed.
- 5
Close the wall and finish
Backer board, waterproofing and tile go on, then the trim.
Closing a wall before inspection is the most expensive mistake in a remodel. Ask your plumber to hold the schedule for the inspector.
Planning a bathroom remodel?
Call the 24/7 line or ask about a plumbing visit before the wall is closed.
Melrose note: permits, fees and inspection days
Melrose Inspectional Services issues plumbing and gas permits. You apply online through the city's permit portal, and the city says staff review can take 2 to 3 weeks depending on volume. The printed permit must be posted at the job site.
Published fees include a $15 administration fee per application, a $30 residential minimum, and $75 for the first four fixtures in a remodel with $10 for each additional fixture. A reinspection costs $50, and work started without a permit is charged triple the fee. Fees can change, so confirm them with the city.
Plumbing inspections run Monday to Thursday, with none on Friday, and are scheduled by phone during a one-hour window at midday on the day you want. Sub-trade permits go only to licensed professionals. Melrose also states that the 10th Edition of the Massachusetts State Building Code took full effect on January 1, 2025. That is the building code, and the plumbing code is a separate set of rules your licensed plumber follows.
Source type: city website
Decide these before demolition
- Valve type and trim. This sets the rough-in depth, so choose before the wall opens.
- Number of shower heads or sprays. More outlets can need larger supply lines.
- Pipe material. Ask for PEX or copper in writing, with the fittings noted.
- Who pulls the permit. Your plumber should handle the permit and the inspection schedule.
- Water heater capacity. A big shower can outrun an undersized tank. Ask about plumbing installation needs up front.
- Access to the shutoff. Know where to shut water off at the start of the job.
Why the rough-in test matters
A shower wall hides its plumbing for decades. If a fitting is weak, the leak will rot framing and ruin tile before anyone sees a wet spot. The pressure test catches that when fixing it takes minutes instead of a demolition.
Ask to watch the test or at least see the gauge. A stable gauge over a set period means the lines hold. A falling gauge means a bad crimp or joint, and that needs fixing before the inspector arrives.
If you are planning bathroom work in another town, check with that town's building office for its permit and inspection steps. We also serve Stoneham and Wakefield.
Waterproofing and the wall behind the valve
Plumbing in a shower wall sits behind a waterproofing layer, and the valve has to line up with it. If the rough-in valve sits too deep or too shallow, the trim does not seat and leaks into the wall. A good plumber measures from the finished wall surface, not the stud.
Valve placement also affects usability. Most people set the valve about waist height so it can be reached without stepping under the spray. The shower arm goes higher and needs solid blocking, because a loose arm pulls on the pipe over time.
Ask about access. A panel on the other side of the wall, such as in a closet or hallway, makes later valve repairs far easier than cutting through tile.
PEX details that matter
PEX connections use crimp rings, clamp rings or push-fit fittings. Each system has its own tool and its own rules. Mixing parts from different systems is a common source of leaks, so ask your plumber which system is going in.
Support matters too. PEX needs clips or straps at regular intervals so it does not sag or rub against framing. Where it passes through studs, protective sleeves or plates stop nails and screws from hitting it later.
Keep a photo record before the wall closes. A picture of the pipe layout helps anyone who drills or repairs in that wall years later.
Hot water and shower performance
A new shower often exposes old problems. Low flow at the head can come from a partly closed shutoff, a clogged cartridge or undersized supply pipe. If the new valve is not the issue, the pipes feeding it may be.
Check the water heater too. A body-spray shower can draw hot water faster than a small tank can supply, and the temperature drops partway through. Talk through the fixtures you plan to run at once before you order parts.
Finally, ask about shutoff stops at the shower. A service stop on each supply makes later cartridge changes far less messy.
Questions we hear
Yes, when installed with approved fittings and tested. PEX is widely used for hot and cold supply lines. Keep it out of direct sunlight and away from sharp edges and heat sources.
Ask Inspectional Services whether your scope needs a permit. Melrose issues plumbing permits through that office. Confirm your scope with the office before starting. Sub-trade permits go to licensed professionals.
Plumbing and gas inspections run Monday to Thursday, with no Friday inspections. They are scheduled by phone in a one-hour window at midday on the day you want, so plan ahead.
The city lists a triple fee for work started without a permit. That is on top of the delay to your schedule. Wait for the permit before you open the wall.
Yes, with approved transition fittings. A mixed system is common in remodels where the existing pipes are copper and the new run is PEX.
A new PEX line may carry a faint plastic taste for a few days. Flush the lines before use. Ask your water supplier if you have specific concerns about water quality.