Plumbing During a Renovation: What to Plan Before the Walls Are Open

A renovation is the best opportunity you will have to deal with the plumbing behind your walls and under your floors. Once the new tile and cabinets are in, fixing old pipes means tearing them out again. Planning the plumbing early saves money and headaches.

Evaluate what you have

Before finalizing a design, find out what kind of piping is in the building:

• Galvanized steel water lines corrode from the inside, reduce water pressure, and often leak at joints. Many older homes in Queens, Brooklyn, and across Long Island still have them.
• Lead water lines may be present in older buildings, sometimes including the service line.
• Cast iron drains can crack or corrode, especially horizontal runs.
• Old copper may be in good shape, or it may have pinhole leaks.
• Plastic piping such as PEX or PVC is common in newer work.

If walls are being opened anyway, replacing old supply and drain lines in that area is usually worthwhile.

Moving fixtures: what it really involves

Relocating a sink, toilet, shower, or appliance is one of the biggest drivers of plumbing scope:

• Drains need slope. Waste lines must slope continuously toward the main drain. Moving a toilet or shower far from the stack can require raising the floor or opening ceilings below.
• Venting. Every fixture needs proper venting so drains flow and sewer gases stay out. New locations may need new vent lines.
• Toilets need a large drain and are the hardest fixture to move.
• Structure. Joists and beams limit where pipes can run. Cutting or notching framing must follow code limits.
• In apartment buildings, connections to building risers may limit where fixtures can go, and the co-op or condo board will have its own requirements.

Keeping wet areas near existing plumbing is usually the most cost-effective approach.

Water pressure and supply

If you are adding bathrooms or upgrading to a large shower system, make sure the water supply can handle it. That may mean larger supply piping within the home or, in some cases, a larger service line. Consider where the water heater is and how long it takes for hot water to reach new fixtures; a recirculation system may help.

Shutoff valves and access

• Install accessible shutoff valves for every fixture.
• Consider adding shutoffs for each bathroom or zone so one area can be serviced without shutting off the whole building.
• Plan access panels for shower valves, whirlpool pumps, and cleanouts.

Gas lines

If the renovation includes a gas range, dryer, or new heating equipment, plan the gas piping at the same time. New gas piping requires testing and approval by the building department and, in NYC, DOB Gas Authorization before the utility turns on gas.

Drains and waterproofing

• Bathrooms on upper floors need a properly installed shower pan or waterproofing membrane.
• Consider floor drains in laundry areas.
• Basement bathrooms below the sewer level may need an ejector pump.
• In areas prone to backups, a backwater valve may be worth discussing.

Permits

In New York City, most plumbing work beyond simple fixture replacement requires a Licensed Master Plumber to file with DOB; minor work may qualify for a Limited Alteration Application. Co-op and condo buildings also require board approval and often insurance certificates. On Long Island, town or village building departments issue permits for plumbing alterations, and many require plans for bathroom and kitchen remodels. Check requirements before work starts so inspections can happen while walls are open.

Don't forget the hidden items

• Asbestos pipe insulation is sometimes found in older buildings. Do not disturb it; have suspect materials tested first. See our guide to asbestos and renovations.
• Insulate pipes in exterior walls to prevent freezing.
• Take photos of open walls before they are closed up. They are useful for future work.

A good plan sets up the whole project

Plumbing affects layout, budget, and schedule more than most people expect. Settling plumbing decisions before finishes are ordered keeps a renovation on track, whether it is a Manhattan apartment, a Brooklyn brownstone, or a home in Nassau or Suffolk.

This article is general information for property owners, not legal or engineering advice. Rules and procedures change; confirm current requirements with the agency or utility involved.