General requirements: materials, protection and workmanship

On the fourth floor, the framing crew had cut a notch through a steel stud track to let Maya's copper branch pass. The notch was rough, the copper sat against a sharp edge, and there was no sleeve. Luis pointed at it without saying anything. Maya knew the answer before he asked the question: the pipe was not protected, it could wear through where it rubbed, and the inspector would write it up. She cut a grommet, protected the pipe and filed the edge. Luis nodded. "That one isn't in the drainage section or the water section," he said. "It's in the general rules. People forget them because they apply everywhere."

This lesson covers the general requirements of the plumbing code: rules that apply to every system, not just to drainage, venting or water supply. They deal with materials, the protection of pipes from damage, freezing and corrosion, support, structural safety when cutting and notching, workmanship, and how new work connects to existing systems. Many failed inspections come from these rules, because they are easy to overlook while concentrating on sizes and slopes.

Where the general rules live

In the IPC, the general requirements are in Chapter 3, General Regulations. It covers the general rules that apply to the whole plumbing system: connections to sewer and water, protection of pipes and components, trenching and backfilling, structural safety, rodent-proofing, workmanship, materials evaluation and listing, inspections and tests, and more. Ohio keeps Chapter 3 with some changes.

Luis's rule of thumb: before you finish a piece of work, ask the general questions. Is the material allowed for this use? Is it supported correctly? Is it protected from damage, freezing and corrosion? Did anyone cut the structure to make room for it, and was that allowed? Can it be tested and serviced? Is the workmanship neat? If any answer is no, the work is not finished.

Materials: allowed for this use

The code controls materials in two ways. It requires that materials meet the referenced standards, as Lesson 1 explained, and it says which materials are permitted for which uses. A pipe that is perfectly good for one job can be forbidden for another.

• Drainage materials differ from water supply materials. A drainage pipe is not rated for pressure, and a water pipe must be suitable for drinking water.
• Some materials are limited by location: below ground, above ground, inside the building, in a return air plenum or in a high-rise.
• Some materials are limited by temperature: hot water, water heater relief discharge or commercial dishwasher waste.
• Products in contact with drinking water must be certified for that use and must meet lead-free limits.

The IPC lists approved materials for each system in tables, such as tables of materials for building drains, building sewers, water distribution and vents. Ohio keeps those tables with some changes. The building code adds conditions where combustible pipe passes through fire-resistance-rated assemblies or is installed in plenums.

Maya made a habit of checking the material tables whenever she saw a material she did not usually work with, and of checking the marking on every length of pipe before it went into the wall.

Protection from physical damage

Pipes inside walls and floors can be damaged by nails, screws, wear and later work. The code requires protection where pipes are close to the face of framing or pass through members that could cut them.

Where a pipe passes through a hole or notch in a wood stud or joist within a stated distance of the face, the IPC requires a steel shield plate of a minimum thickness on the face of the member, extending beyond the pipe. Where pipes pass through steel framing, they must be protected from abrasion, typically with a grommet or sleeve. Pipes exposed where they could be struck by vehicles or equipment must be protected or located out of harm's way.

• Pipes passing through concrete or masonry walls and floors need sleeves or other protection so the structure's movement does not crush or shear them, and so the pipe can expand.
• Pipes must not be embedded in materials that attack them, and copper and steel must be protected where they are in contact with corrosive soil, concrete or dissimilar metals.
• Plastic pipe must be protected from long exposure to sunlight unless it is rated for it.

Protection from freezing

Water pipes that freeze can split and flood a building, and drains that freeze stop working. The code requires piping to be protected from freezing, whether by location, insulation, heat or depth of burial.

The IPC requires water service piping to be installed below the recorded frost penetration depth or insulated, and building sewers to be protected from freezing. Columbus's local frost depth is around 32 to 36 inches, and the city's standards set the minimum cover for water services. Inside the building, water pipes must not be placed in exterior walls, attics or crawl spaces where they could freeze unless they are protected. In practice, that means placing them on the warm side of the insulation.

At Kingsway Tower, Maya's water branches to the ground-floor commercial space ran near the north wall, over an unheated loading bay. The engineer had shown them insulated and placed above the insulated ceiling, inside the heated space. Maya checked that the ceiling insulation was installed below the pipes, not above them, before the drywall went up.

Support and hangers

Pipes must be supported so that they keep their slope, do not sag, are not strained at joints and can expand and contract. PLB-110 covered hangers in detail. The code sets the minimum: supports at maximum intervals for each material and size, at changes of direction and at the base of stacks, and hangers of material that will not damage the pipe.

• Plastic pipe needs closer support than metal pipe, especially when carrying hot water.
• Vertical stacks need support at their base and at intervals, such as at each floor, so that their weight does not rest on the fittings below.
• Hangers must not cause galvanic corrosion; copper pipe needs copper-coated or isolated hangers.
• Supports must allow thermal expansion in long runs, especially for hot water and plastic pipe.

The program below checks a run of pipe against maximum support spacing, using simplified practice values. Always use the support intervals in the adopted code and the manufacturer's instructions.

# Check hanger spacing on horizontal runs (practice values only, feet)
max_spacing = {"copper up to 1 in": 6, "copper 1-1/4 in and up": 10,
               "PVC drain": 4, "PEX": 32 / 12, "cast iron": 10}
runs = [("copper up to 1 in", 30, 5), ("PVC drain", 24, 5), ("PEX", 13, 4), ("cast iron", 40, 4)]

for material, length, hangers in runs:
    needed = int(-(-length // max_spacing[material])) + 1  # one at each end plus intermediate
    status = "ok" if hangers >= needed else f"add {needed - hangers}"
    print(f"{material:22s} {length:3d} ft, {hangers} hangers, need {needed}: {status}")

copper up to 1 in       30 ft, 5 hangers, need 6: add 1
PVC drain               24 ft, 5 hangers, need 7: add 2
PEX                     13 ft, 4 hangers, need 6: add 2
cast iron               40 ft, 4 hangers, need 5: add 1

Structural safety: cutting and notching

Plumbing often has to pass through structure: joists, studs, beams and slabs. The code protects the structure by limiting how much can be cut, and where. In wood framing, the building code sets limits on the size and location of holes and notches in joists and studs. In steel and concrete, cuts and cores need the structural engineer's approval.

The building codes set limits for notches and holes in wood joists, rafters and studs, such as maximum hole sizes relative to the member's depth and minimum distances from the edges, and the IPC's structural safety section requires that plumbing work not weaken the structure beyond what the building code allows. In larger buildings such as Kingsway Tower, any coring of concrete slabs, cutting of post-tensioned slabs or penetration of steel beams requires the structural engineer's review. Coring a post-tensioned slab without scanning first can cut a tendon, which is dangerous and very expensive to repair.

Engineered products such as I-joists and trusses have their own rules for holes, set by the manufacturer. They often allow larger holes in the web but forbid any cut in the flanges. Never cut a truss or the flange of an I-joist without written approval.

Fire separations and fire stopping

Where a pipe passes through a fire separation or fire-resistance-rated assembly, the opening must be sealed so that fire and smoke cannot pass through. This is a building code requirement that plumbers deal with every day. The fire stop must be a tested system suitable for the pipe material, size and assembly, installed exactly as tested. Plastic pipe needs fire stops that close the opening as the pipe melts, often with intumescent material that expands in heat.

On Kingsway Tower, Northbridge used tested firestop systems for every pipe through the concrete floors and the rated corridor walls. Maya learned to check the system's listing against the pipe material, size and annular space before installing, and to label each penetration so the inspector could check it. A fire stop that is not installed to its tested system is not a fire stop in the code's eyes.

Connections, workmanship and existing systems

The general rules also cover how work is done.

• Workmanship: work must be done in a workmanlike manner, with pipes cut square, reamed, joined according to the manufacturer's instructions and installed straight and level or at the required slope.
• Prohibited joints and fittings: certain fittings and joining methods are forbidden because they obstruct flow or fail, such as fittings that reduce the flow area in the direction of flow in drains.
• Connections to the public systems: the building's drain and water service must connect to the public sewer and water main where they are available, according to the utility's rules.
• Existing systems: additions and alterations must meet the current code for the new work, without making the existing system less safe. Existing work that met the code when installed generally may remain unless it is unsafe.
• Rodent-proofing and sealing: openings where pipes pass through exterior walls and floors must be sealed.
• Toilet facilities for workers: during construction, sanitary facilities must be provided for workers.

Luis's view of workmanship was simple: an inspector who sees neat, square, well-supported work trusts the plumber and looks less hard for problems. An inspector who sees sloppy work starts looking everywhere. Neat work is not just pride; it is time saved.