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Plumbingaka: shutoff valveaka: ball valveaka: gate valveaka: isolation valve

Valve

In Plain English

A device in a pipe that controls whether water or gas flows through — used to shut off, regulate, or redirect flow.

Definition

A mechanical device that controls the flow of liquid or gas in a piping system by opening, closing, or partially obstructing a passageway. Common plumbing valve types include ball valves, gate valves, globe valves, check valves, and pressure reducing valves, each suited to specific applications. Proper valve placement allows isolation of individual fixtures and sections for repair.

Why It Matters in Bidding

Valves are a high-count, high-variation item in plumbing and mechanical takeoffs, and their type, size, and material drive both material cost and the labor to install and access them. Estimators must read specs carefully because a spec change from bronze to forged steel or from gate to ball valves can shift cost significantly. Missed isolation valves also create costly retrofit change orders and code compliance issues.

Example

Estimating a multifamily plumbing rough-in, the estimator counts a shutoff valve at each unit's water entry plus zone isolation valves per riser, pricing 220 quarter-turn ball valves and noting access-panel coordination with the GC.

Related Terms

Main Shutoff ValveBackflow PreventerPressure RegulatorGas Piping

Frequently Asked Questions

They work riser by riser and fixture by fixture, marking each isolation, control, and backflow valve against the plumbing plans and risers diagram, then cross-check against the spec section for required types and ratings. Counting by system rather than by sheet reduces double-counting and catches code-required valves that drawings sometimes omit.
Material and pressure class drive price and labor. A bronze ball valve, a cast-iron gate valve, and a stainless pressure-reducing valve at the same size can differ by several multiples in cost. Spec-required actuators, end connections, and access requirements add further. Estimators must price the exact specified valve, not a generic equivalent.
Yes. Concealed valves typically need access panels or accessible ceilings, which means coordination with drywall, ceiling, and GC scopes. If the bid prices the valve but not the access provision, the cost surfaces later as a change order. Good estimators flag valve access during the bid so responsibility is clearly assigned.

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