In a new building, plumbing is installed in stages. First comes planning and permits, then underground work beneath the foundation, then rough-in plumbing inside the walls and floors, followed by pressure testing and inspections. After the walls are closed up, plumbers return to install fixtures, the water heater, and final connections, and the system is inspected one last time before anyone moves in.
Most people never think about plumbing until something goes wrong. But if you’re building a home, a shop, or a commercial space, you’ll quickly learn that plumbing is one of the first trades on site and one of the last to leave.
That’s because plumbing has to happen in a specific order. Pipes go in before the concrete is poured and again before the drywall goes up, and fixtures only come at the very end. Skip a step or do it out of sequence and you can end up tearing open finished walls.
At Capital One Plumbing in Beaumont, CA, we work with builders, contractors, and property owners on new construction projects. This guide walks through the whole process in plain English, so you know what’s happening and why.
Step 1: Planning and Design
Every good plumbing system starts on paper, long before anyone picks up a wrench.
Plumbers and designers review the building plans to figure out:
- Where kitchens, bathrooms, laundry rooms, and utility spaces will go
- How many fixtures the building needs (sinks, toilets, showers, tubs, hose bibs)
- Where the water supply will enter the building
- Where wastewater will exit to the sewer or septic system
- Where the water heater and any gas lines will go
- Whether the building needs fire sprinklers or other specialty systems
Good planning saves money. Stacking bathrooms above one another or placing them back to back, for example, can shorten pipe runs and simplify the work. A plumber who’s consulted early can often spot problems on the drawings, long before they turn into expensive changes on site.
Step 2: Permits and Code Requirements
Plumbing in new construction is regulated, and for good reason. Pipes carry the water you drink and the waste you want safely removed, so mistakes can affect health and safety.
In California, plumbing work must follow the California Plumbing Code along with building and energy standards, and your local building department typically requires permits and inspections. In Beaumont, that generally means working with the City of Beaumont or Riverside County, depending on the property’s location. Requirements can change, so your contractor should confirm the current rules before work begins.
Some things that are regularly addressed in new California construction include:
- Water-efficient fixtures: State green building standards set limits on how much water toilets, faucets, and showerheads can use.
- Lead-free materials: Pipes, fittings, and fixtures that carry drinking water must meet strict lead-free requirements.
- Fire sprinklers: New homes in California generally need residential fire sprinkler systems, which are often tied into the plumbing plan.
- Backflow prevention: Devices that stop contaminated water from flowing backward into clean water lines are required in many situations.
A licensed plumber pulls permits, follows the code, and schedules the inspections so the project keeps moving.
Step 3: Underground Plumbing (Before the Foundation Is Poured)
If the building sits on a concrete slab, the first physical plumbing work happens below the floor. This is called underground or “under-slab” plumbing, and it has to be finished before concrete goes down.
During this stage, plumbers:
- Dig trenches where needed
- Install the main drain lines that carry wastewater out of the building
- Place drain pipes, floor drains, and the connections (called stub-outs) that will later feed toilets, tubs, showers, and sinks
- Set the sleeves and penetrations where pipes will pass through the foundation
- Install any underground water supply lines
The pipes used for drain lines are usually plastic, such as ABS or PVC, depending on code and local practice. Each line needs the correct slope so gravity can do its job, and getting that wrong is one of the costliest mistakes in plumbing. Once the slab is poured, those pipes are locked in place.
Inspection and testing: Before the trenches are covered, the underground plumbing is tested, often with water or air pressure, and inspected. Only after it passes can the concrete crew move in.
If the building has a crawl space or basement instead of a slab, similar work happens in those areas.
Step 4: Rough-In Plumbing (Inside the Walls and Floors)
Once the framing goes up and the walls, floors, and ceilings are open, plumbers return for the rough-in. This is the stage where the hidden “skeleton” of the plumbing system is installed.
During rough-in, plumbers:
- Run water supply lines (hot and cold) to every fixture location
- Install drain, waste, and vent (DWV) pipes that carry wastewater out and let air into the system so it drains smoothly
- Set tub and shower valves and install shower pans or tub bodies where required
- Mount boxes for washing machine connections
- Run gas lines for appliances like stoves, dryers, and water heaters (often by a plumber licensed for that work)
- Frame in or position pipes for the water heater and any future connections
What Pipes Are Used?
Common materials in new construction include:
- PEX: A flexible plastic pipe widely used for water supply because it’s durable, resists corrosion, and is quicker to install, with fewer fittings than rigid pipe.
- Copper: Long trusted for its durability and longevity, though it’s more expensive and more labor-intensive.
- CPVC: Rigid plastic pipe used in some water supply applications.
- ABS and PVC: Common for drains, waste, and vent lines.
- Cast iron: Sometimes used for drain lines where quieter operation is desired, such as in multi-story buildings.
The right choice depends on the type of building, the local code, your budget, and your water conditions.
Why Venting Matters
Vent pipes usually run up through the roof. They don’t carry water. They let air flow so that drains empty smoothly and sewer gases don’t back up into the building. A poorly vented system can cause gurgling drains, slow flow, and unpleasant smells.
Step 5: Pressure Testing and Rough-In Inspection
Before anyone closes up the walls, the system gets tested and inspected. This is one of the most important steps in the whole process.
- Water supply lines are usually pressurized and checked for leaks.
- Drain and vent systems are tested to confirm that connections are tight and working as designed.
- Gas lines are tested separately for safety.
A building inspector then reviews the work to make sure it meets code. If something fails, it’s fixed and re-inspected, and this is the best possible time to discover a problem, when the pipes are still easy to reach.
Only after the rough-in passes can insulation and drywall go up.
Step 6: Insulation, Drywall, and Other Trades
Now the building starts to look like a building. Insulation goes in, drywall closes the walls, and other trades such as electrical, HVAC, flooring, and cabinetry do their work.
Plumbers aren’t idle during this time. They coordinate with the other trades, because pipes, ducts, and wires all compete for space inside the walls. Good communication on site prevents conflicts, like a vent pipe colliding with a duct or a drain line running where a beam needs to go.
Step 7: Finish Plumbing (Trim-Out)
When the walls are painted, cabinets are in, and floors are nearly finished, the plumbers come back for the “trim-out” or finish stage. This is the part most people picture when they think of plumbing.
During the finish stage, plumbers install:
- Toilets
- Sinks and faucets
- Showerheads, tub spouts, and trim
- Kitchen fixtures, garbage disposals, and dishwasher connections
- The water heater, whether tank or tankless
- Hose bibs and exterior fixtures
- Washing machine connections
- Water softeners, filtration systems, or recirculation pumps, if included
Each fixture is connected, sealed, and tested for leaks, and handles, drains, and supply stops are checked for proper operation.
Step 8: Connecting to Water and Sewer
At some point in the project, the building has to be tied into the public utilities, or to a well or septic system if it’s in a rural area.
- Water service line: Connects the building to the water main or well. In the Beaumont area, the local water provider typically sets requirements for meters, connections, and backflow protection.
- Sewer lateral or septic system: Connects wastewater lines to the municipal sewer or to a septic system, depending on the property.
- Gas service: Connects to the utility’s gas line for buildings using natural gas or propane.
This stage often involves coordination with the utility company and the building department, so timing matters.
Step 9: Final Inspection and Testing
Once everything is installed, the building gets a final plumbing inspection. Inspectors typically check that:
- Fixtures are installed correctly and working properly
- Water pressure and temperature are within acceptable ranges
- The water heater is installed safely, with proper venting, seismic strapping (where required), and relief valves
- Drains flow freely and there are no leaks
- Required backflow devices and shutoff valves are in place
When the system passes, it’s signed off, and the building can move forward to occupancy.
Step 10: Walkthrough and Homeowner Orientation
A good plumber doesn’t just disappear after the final inspection. A walkthrough helps you understand your new system, including:
- Where the main water shutoff valve is, and how to turn it off in an emergency
- Where the water heater shutoff and gas valves are
- How to care for fixtures and prevent clogs
- Where to find warranty and product information
- What routine maintenance to keep in mind
Knowing where your main shutoff is can save you thousands of dollars if a pipe ever fails.
Residential vs. Commercial Plumbing in New Buildings
The basic order of work is similar, but the details differ.
| Residential | Commercial | |
|---|---|---|
| Scale | Fewer fixtures, simpler layouts | More fixtures, larger pipes, complex layouts |
| Systems | Standard supply, drain, vent, water heater | May include grease interceptors, backflow assemblies, larger water heaters, specialty systems |
| Code requirements | Residential code | Commercial code, plus accessibility and health requirements |
| Timeline | Typically shorter | Often longer, with more coordination between trades |
Restaurants, salons, medical offices, and retail spaces each have their own plumbing needs, so planning with a plumber who understands your business type matters.
Common Mistakes in New Construction Plumbing (and How to Avoid Them)
- Not involving the plumber early. Waiting until after the design is finished can mean costly changes later.
- Poor coordination between trades. Clashes between pipes, ducts, and framing can cause delays.
- Cutting corners on materials. The cheapest pipe isn’t always the cheapest in the long run.
- Skipping or rushing inspections. Hidden problems become expensive ones once walls are closed.
- Forgetting future needs. Adding a stub-out for a future bathroom or an outdoor kitchen is far cheaper during construction than after.
- Hiring an unlicensed plumber. Unlicensed work can fail inspections, void warranties, and create safety risks.
How to Choose a Plumber for a New Construction Project
When comparing plumbing contractors, look for:
- A valid California contractor license, which you can verify online through the Contractors State License Board (CSLB)
- Insurance and workers’ compensation coverage
- Experience with new construction, not just repairs
- Clear written estimates and scope of work
- References and examples of past projects
- Good communication, because schedules and coordination are everything in construction
- Knowledge of local codes and inspectors
Frequently Asked Questions
How long does it take to install plumbing in a new building?
It depends on the building’s size and complexity. Plumbing happens in phases that are spread over the construction schedule, from underground work at the start to finish work near the end, so there’s no single timeline. Your plumber can give you a schedule for your specific project.
What is plumbing rough-in?
Rough-in is the stage where supply, drain, and vent pipes are installed inside walls, floors, and ceilings before they’re closed up. Fixtures like sinks and toilets are connected later during the finish stage.
What’s the difference between rough-in and finish plumbing?
Rough-in is the hidden piping inside the structure. Finish plumbing, or trim-out, is the installation of visible fixtures, faucets, appliances, and the water heater.
Is PEX or copper better for new construction?
Both can work well. PEX is flexible, corrosion-resistant, and often faster to install. Copper is long-lasting and trusted but typically costs more. The right choice depends on your project, budget, local code, and water quality, so ask your plumber for a recommendation.
Do new buildings need plumbing inspections?
Yes. Plumbing in new construction typically goes through multiple inspections, including underground, rough-in, and final, to confirm compliance with code.
Can I add plumbing after the building is finished?
Yes, but it’s usually more expensive and disruptive than doing it during construction. If you might want a future bathroom, wet bar, or outdoor kitchen, it’s smart to ask about roughing in lines now.
Why does the plumber come back more than once?
Plumbing is done in phases because the work has to be sequenced with other trades. Pipes go in before walls close, and fixtures go in after finishes are complete.
Build It Right from the Ground Up
A well-installed plumbing system is something you rarely notice, and that’s exactly the point. When it’s planned well, built to code, and inspected carefully, it quietly does its job for decades.
At Capital One Plumbing in Beaumont, CA, we work with builders, contractors, and property owners to install new construction plumbing that’s done right from the first trench to the final fixture. If you’re planning a new build, we’d be glad to review your plans and talk through your options.
Contact Capital One Plumbing today to discuss your new construction project.
This article provides general information and isn’t a substitute for professional advice. Code requirements, permitting rules, and inspection procedures vary by location and change over time. Confirm current requirements with your local building department and a licensed contractor.