Service Sink (Mop Sink)
A deep floor or wall basin for filling and emptying mop buckets, counted each.
Quick Answer
A service sink, also called a mop sink or mop basin, is a deep fixture set in a janitor closet or utility room for filling mop buckets and disposing of dirty water. Plumbing codes call for one in many occupancies, and estimators count it each, with its faucet, drain and trap.
The Full Picture
A service sink is a deep basin used by custodial staff to fill mop buckets, rinse mops and dump dirty water, so it is kept out of sinks used for hand washing. The common forms are a floor-mounted mop basin (also called a mop sink or mop basin) and a wall-hung service sink with a trap standard, often called a slop sink. Floor basins are commonly square, around two to three feet on each side, set in a janitor closet, and made of molded stone, terrazzo, or fiberglass. Wall-hung types are cast iron or vitreous china. The fixture schedule names the type, size and material.
Plumbing codes generally call for a service sink or equivalent in many building types so that cleaning staff have somewhere other than a lavatory to dispose of wastewater. The International Plumbing Code lists the requirement in its fixture table by occupancy, and local adoption and amendments apply. The engineer shows required service sinks on the plans and in the fixture schedule, so the estimator counts what is drawn, and in many buildings the janitor closet on each floor or wing gets one. The ADA Standards chapter 6 covers lavatories and sinks, and the design team decides how accessibility requirements apply to a given service sink.
On plans, a service sink appears in the janitor closet or custodial room on the floor plan, tagged with a fixture mark, and in the plumbing fixture schedule and riser diagram. The schedule gives the basin type and size, the faucet, the drain, and the trap size, and the spec sets the material and any accessories. A janitor closet is small and easy to overlook when scanning a plan, and one is often placed on each floor, so counting should be by floor rather than by building.
The takeoff unit is each, by type. A complete installation commonly includes the basin, a service faucet with a hose connection and a vacuum breaker, a drain, a trap and trap arm, and accessories such as a hose and bracket, a mop hanger and a wall guard. Supply stops, hot and cold rough-in, and the waste and vent connection are carried with the plumbing piping. Common mistakes include pricing a standard sink instead of the specified service basin, missing the accessories, counting only the closets on typical floors and missing ones in basements, loading docks and trash rooms, and leaving out floor drains or wall protection that the janitor closet requires.
Real Examples
Common Misconceptions
People assume: A service sink is just a large kitchen sink.
Actually: It is a different fixture, with a deep basin, a floor or wall mounting, a service faucet and often a trap standard. It is priced under its own schedule tag.
People assume: Every building needs a service sink on every floor.
Actually: Requirements vary with occupancy and the adopted code, and the design shows how many are needed. The estimator counts what is on the plans and the fixture schedule.
People assume: The basin is the whole cost.
Actually: The faucet, drain, trap, accessories and rough-in are separate lines. In a small closet the accessories and wall protection can matter.
Does MeltPlan Solve This?
Partially — adjacentService sink counts by floor and room are taken from the plumbing plans and fixture schedule, and MeltPlan's takeoff service covers that counting work: AI pulls quantities from plans and US-based experienced estimators review and adjust them. Matching each count to the schedule and the spec's accessories stays with your estimator.
Get fixture counts taken off from your plumbing plans →Frequently Asked Questions
What is a service sink?
A deep basin used by custodial staff to fill mop buckets and dump dirty water. It is usually in a janitor closet, and it is also called a mop sink or mop basin.
Is a service sink the same as a mop sink?
Yes, in everyday use. A mop sink is typically a floor-mounted basin, and a service sink can also be a wall-hung type, but the terms are used interchangeably on plans.
How is a service sink counted in a takeoff?
Each, by type, from the fixture schedule and the plan tags. The faucet, trap, drain and accessories are counted or priced with it.
Do codes require a service sink?
Many occupancies call for one under the adopted plumbing code, with the count set by the design. Check the local code and the plans.
What is usually included with a service sink?
A basin, a service faucet with a vacuum breaker, a drain and trap, and often a hose, bracket, mop hanger and wall guards, depending on the spec.