The five-foot line: plumbing and site utilities

Most sets draw the line five feet outside the building. Inside it, the pipe belongs to the plumbing package. Outside it, to site utilities. Two proposals arrive, both honour the convention, both are competently priced, and the tie-in to the public main is in neither of them.

That is the characteristic failure of this boundary, and it is worth being precise about why it happens. It is not that somebody forgot an item. It is that the same run of pipe appears on two drawing sets prepared by two designers for two different readers, and the sheets disagree about what happens in the six feet where they overlap. The plumbing sub priced the plumbing set. The site sub priced the civil set. Both did their job.

This guide is for a GC estimator leveling plumbing and site utility packages on building work with a public utility connection. On a campus tie-in or a private system the specific items change, the reading method does not.

What the line actually is

The five-foot convention is a specification habit, not a code rule. Plenty of institutional owners write it down: university and agency Division 22 standards routinely state that the split between Division 22 and Division 33 occurs five feet outside the exterior face of the building, and that plumbing carries potable water, sanitary and storm to that point. When an owner publishes that, both bidders are reading the same line.

The trap is that the plumbing code draws its own line somewhere else. Under the IPC the building drain extends 30 inches beyond the exterior wall and the building sewer begins there. Under the UPC that transition sits at two feet. Neither is five feet. So on a project the code boundary, the specification boundary and the contract boundary are three different things, and only the last one determines who owes you a price.

When the specification says nothing, two reasonable subs can place the line differently, and you will not discover the disagreement by comparing prices. You discover it by comparing what each proposal says it starts and stops at, which is a different exercise.

The items that live in the gap

The tap to the main. Cutting into the public line, the corporation stop, the tapping sleeve and valve. Frequently performed by the utility or by a contractor the utility approves, and just as frequently assumed by both of your bidders to be the other's problem, or the owner's.

The meter, the vault and the domestic backflow assembly. These sit close to the boundary and move across it depending on the designer. The backflow assembly in particular gets priced by the plumbing sub when it is drawn inside a mechanical room and by the site sub when it is drawn in an exterior pit.

The sanitary tie-in. Connecting to a main or coring into an existing manhole, including the invert work and any required traffic control if the manhole is in a street.

The cleanout at the building line. Small, cheap, and a standing argument because it is exactly on the boundary.

Roof drain leaders to the storm system. The leader comes down inside the building as plumbing work, then becomes a site storm run. The transition point is frequently drawn on neither set clearly.

The grease interceptor. Whether it is an in-building unit or an exterior tank changes which package it belongs to, and a late relocation moves it between subs after both have priced.

The fire service lead-in is the same problem with a third party in it, and it is covered in the sprinkler assumptions rather than repeated here.

The excavation question nobody asks

The pipe is one ownership question. The hole it goes in is another, and it is asked far less often.

For underground work inside the building footprint, somebody has to trench, bed, backfill and compact, and somebody has to pay for the compaction testing and the slab patch afterwards. The plumbing sub may carry all of it, some of it, or none of it, depending entirely on local custom and what their proposal says. On a job where the excavation sub mobilizes once and leaves, a plumbing bid that excluded its own trenching creates a remobilization nobody priced.

The related items follow the same pattern: sleeves and blockouts through footings and foundation walls sit between concrete and plumbing, dewatering during underground installation is usually excluded by everyone, and trench safety with a competent person on site is real cost that appears on a proposal only when the bidder is being careful.

Gray zones to read for by name

Rock and unsuitable soils. Almost always excluded or made an allowance. The question is whether the exclusion is priced consistently across both bids and whether your carry matches the geotech.

Tap fees and utility charges. Often an owner cost, often assumed so by both subs, occasionally not an owner cost at all. Confirm against the front end rather than the trade sections.

Permits. The plumbing permit, the utility connection permit and a right of way permit with traffic control are three different things with three different owners.

Testing and disinfection. Hydrostatic and air testing, disinfection and bacteriological clearance on domestic water, video inspection on sanitary. Each is a line somebody carries and each is a line somebody excludes.

Temporary water and sanitary. General conditions on some jobs, a trade line on others.

What to freeze before the bid goes in

Three sentences in the solicitation cost nothing and remove most of this.

State the boundary in words. "The plumbing contractor's scope includes all underground piping to a point five feet outside the building line, including the cleanout at the building line" resolves what a sheet note does not.

Name who carries the connection. The tap, the meter, the backflow assembly and the fees, explicitly assigned, even if the answer is that the owner carries them.

Say who digs inside the building. One sentence, and it prevents the remobilization argument entirely.

Then read the proposals for what they start and stop at rather than for what they include. On this boundary the exclusions are usually honest and the overlap is where the money hides.

Where Piper fits

Piper is the AI operating system for preconstruction. It builds the trade scope from the drawings, specifications, addenda and your company's standards, then reads the proposals you received against that scope rather than only against each other, showing what each one includes, excludes, qualifies or leaves silent, with the clause or sheet behind every finding.

This boundary is a good illustration of why comparing bids to each other is not enough. Two proposals can agree with one another perfectly and still leave the tap unowned, because the gap is not visible in either document alone. It is visible against the project: the civil set, the plumbing set and the front end read together, which is what one shared understanding of the project makes possible.

Piper does not assign the scope, negotiate the boundary or decide what to carry. It makes the unclaimed six feet visible while the price can still move.

Sources

• Institutional Division 22 standards that state the Division 22 to Division 33 split at five feet outside the building, including Cal Poly, Washington State University, the University of Minnesota and Iowa State University
• International Plumbing Code, Chapter 2, definition of building drain (30 inches beyond the exterior wall)
• Uniform Plumbing Code, building drain to building sewer transition at two feet