Bar drainage and waste connection

Takes away everything the bar puts down — drip trays, backflush, ice melt, wash-up, treatment discharge and the floor — reliably enough that nobody has to think about it during service.

Gravity, a water seal and air. Every fixture drains by fall, so a run needs continuous slope from the fixture to the stack; a run that flattens, or that was set level to clear an obstruction the joiner discovered late, holds water and solids and becomes the place that blocks. A trap holds a water seal that keeps sewer gas out of the room, and a trap that dries out — a floor gully that only sees ice melt, a drain used once a week — stops being a seal and becomes a vent. Venting matters for the same reason: a discharge that fills the pipe pulls a vacuum behind it and can siphon a trap dry, which is why the traps that fail are often the ones nobody uses rather than the ones that work hardest. And where a drain serves equipment connected to the potable supply, the connection is normally made with a deliberate physical break so that waste can never be drawn back into the water, which in most jurisdictions is a code requirement rather than a supplier's choice. What a BAR adds to all of this is an unusual loading. Milk proteins and fats from steam-wand purges and jug rinsing, sugar and syrup, coffee grounds and fines, and in some installations a continuous treatment discharge running whether anyone is working or not. That mixture congeals on cool pipe walls in a way a domestic kitchen's waste does not, and it does it out of sight. Slope, pipe sizes, venting, trap type, grease interception and backflow protection are all a licensed plumber's design and are governed by the local authority — this site states none of them, and nothing here should be read as a dimension.

• Design drainage at the same time as the water supply and before the joinery is fabricated, because every decision in this category has a drain on the other side of it. Reverse osmosis sends concentrate to drain continuously, a regenerating softener discharges brine on every cycle, drip trays and backflush discharge at every clean, and the ice well discharges all day. Adding a drain after the cabinetry is built is one of the most expensive changes on the whole fit-out.
• List every discharge in the bar before anyone sizes anything. Espresso machine drain and drip tray, steam-wand purge, group backflush, ice well and ice machine, wash-up sink, hand basin, boiler tray, treatment discharge, floor. A plumber can only design for what they are told exists, and the ones that get left off the list are always the continuous ones nobody thinks of as fixtures.
• Decide plumbed or hand-emptied per fixture, honestly, and decide it against how fast that fixture actually fills. A hand-emptied tray costs nothing to install and costs a recurring task forever; a plumbed one is the exact reverse and commits the equipment position permanently. Neither is right in general and both are right somewhere.
• Tell the plumber what a bar actually discharges, because it is not what a domestic kitchen discharges. Milk proteins and fats, sugar and syrup, coffee grounds and fines, all of it warm, congealing on cool pipe walls out of sight. Then put a hot flush of the equipment drain line into the closing routine, so the design assumption and the operating routine agree with each other.
• Protect the potable supply, and treat that as a professional's decision rather than a supplier's default. Any equipment drain downstream of a treated water supply raises a backflow question, and the physical break that answers it belongs to a licensed plumber and the local authority. This is life-safety adjacent and it is not a detail to be resolved on site by whoever arrives first.
• Keep every trap wet, and name the ones that will not stay wet on their own. A floor gully that only receives ice melt in summer dries through a quiet winter and becomes a smell that nobody can locate, and the fix is a jug of water in the closing checklist rather than an investigation.
• Put the drain where the mess is, not where the plumbing was convenient. The knock box, the ice well, the wash-up and the espresso lane generate almost all of it, and a drain sited for the builder's ease guarantees that liquid is carried across the bar by hand for the life of the venue — which is also how floors get wet.
• Make cleaning access physically possible before you sign off the design. A removable grate somebody can actually lift, a rodding point that is not behind a fixed cabinet, and a run that can be flushed without dismantling anything. A drain that cannot be reached is a drain that is cleaned only after it has already blocked, during service.
• Confirm every dimension and requirement with a licensed plumber and let the local authority govern: falls, pipe sizes, venting, trap type, interception and backflow protection. This site deliberately states none of them, and any figure that appears in a supplier's drawing is a proposal to be checked rather than a specification to be trusted.