Condensate Management

Vacuum Drain

Liquid out of your vacuum system, with suction running and the vacuum never broken.

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A stainless steel vacuum drain with its chamber, valves, gauges and control block on a mounting frame

Product overview

Empty vacuum vessels without breaking the vacuum

Our vacuum drain removes liquid from vessels running below atmospheric pressure: vacuum filter bowls, liquid separators, knockout pots, vacuum receivers and pipework low points. It discharges water, condensate, coolant or aspirated process fluid while your vacuum system keeps running.

At 100 mbar absolute, the atmosphere outside the vessel is 913 mbar higher than inside it, so an open valve simply draws air in and holds the liquid back. Draining by gravity alone would need a sealed water column of about 9.3 m. The vacuum drain uses an airlock instead, and at no point is there an open path between your vacuum system and atmosphere.

A float triggers each cycle, so the drain runs as often or as rarely as the inflow needs. In medical and laboratory systems the discharge can be piped to a sealed collection container, keeping potentially infectious fluid contained.

A stainless steel vacuum drain with its chamber, valves, gauges and control block on a mounting frame
  • 913 mbarPressure difference at 100 mbar absolute
  • About 9.3 mWater column that gravity draining would need
  • Under 20 msFor a 100 m³/h pump to clear a cycle's air at 200 mbar
  • About 0.03 %Added gas load, one cycle a minute at 200 mbar

Benefits

The problems it solves

Liquid cannot leave a vessel under vacuum by gravity, and most vacuum processes draw liquid in. Here is what that does to a system, and how the drain deals with it.

  • Stopping to drain by hand

    The problem

    Manual draining means isolating the vessel, breaking vacuum, emptying it and re-evacuating it, so dependent processes stop.

    How it solves it

    Filters, separators and receivers empty without stopping suction at your points of use.

  • Pumps damaged by liquid

    The problem

    Water emulsifies the oil in oil-sealed pumps and corrodes dry pump rotors, and a liquid slug overloads any positive displacement pump.

    How it solves it

    Liquid is removed at the filters and separators before it can reach your pump.

  • Flooded filter elements

    The problem

    A bowl that fills until liquid reaches the element wets the medium, cutting suction at the points of use.

    How it solves it

    Bowls stay empty and elements stay dry, holding pressure drop at its design value.

  • Air leaks at the drain

    The problem

    Every air leak into a vacuum system uses pump displacement that would otherwise hold the vacuum.

    How it solves it

    Each cycle admits only the air trapped in a small chamber, so the vacuum at the vessel does not fall measurably.

  • Liquid that turns back to vapour

    The problem

    Liquid left standing under vacuum evaporates back into the gas stream: each kilogram becomes about 28 m³ of vapour at 50 mbar and 33 °C.

    How it solves it

    Liquid leaves the system as liquid, so your pump does not have to evacuate its vapour.

  • Infectious discharge

    The problem

    Liquid from bacteria filters in medical and laboratory vacuum is potentially infectious.

    How it solves it

    A single piped discharge feeds a sealed collection container, keeping contaminated liquid away from your staff and plant room.

Where it’s used

Wherever vacuum draws in liquid

Most processes that use vacuum draw in liquid or vapour with the air. The drain sits wherever that liquid collects, upstream of the pump.

  • Hospital beds lined up along a bright corridor

    Hospitals

    Central medical vacuum plant with duplex bacteria filters and drainage flasks upstream of the pumps, as described in HTM 02-01.

  • Dental handpieces and instruments on a dental unit

    Dental practices and clinics

    Dental suction draws saliva, water spray and blood with the air, a continuous liquid load at the separator.

  • Test tubes of coloured chemicals in a laboratory rack

    Laboratories

    House vacuum for filtration, rotary evaporators, vacuum ovens and desiccators, all releasing solvent or water vapour into the line.

  • Wine bottles moving along a bottling line

    Food packaging and dairy

    Vacuum packaging of meat, fish and cheese draws moisture and brine into the pipework, and milking installations collect milk and wash water.

  • Blue plastic bottle caps in a moulded tray

    Plastics extrusion

    Vacuum calibration tanks for pipe and profile draw water spray into their vacuum lines continuously.

  • Yellow tablets spilling from a medicine bottle

    Pharmaceutical and chemical processing

    Vacuum drying, distillation, evaporation and degassing release vapour that condenses in cooler pipework and filters.

Also CNC machining and woodworking, printing and paper converting, electronics assembly, vacuum conveying and lifting, and composites manufacturing.

How it works

An airlock for liquid

The drain never opens your vacuum system to atmosphere. A small chamber takes the liquid at system vacuum, is sealed off and vented, and lets the liquid run out under its own weight.

How a vacuum drain works: liquid runs by gravity from a vacuum filter into a chamber held at system vacuum; when a float senses the chamber is full, the inlet valve and equalisation line close, a vent lets atmospheric air in, and the outlet valve opens so the liquid drains under its own weight; the outlet and vent then close, the pump returns the chamber to vacuum and the inlet reopens. The chamber is never open to the vacuum system and atmosphere at the same time. From processTo vacuum pump Vacuum filteror separator Inlet valveEqualisation line VentAtmosphere Outlet valveTundish or container Chamber 100 mbar absChamber 100 mbar abs Chamber at atmospheric 0.1 L → 1.0 L at 100 mbar 12345Air and vapour to the pumpCollected liquidAir displaced or admittedValve openValve closedYour equipment

  1. 1. CollectThe chamber sits at system vacuum, so liquid runs into it by gravity and lifts the float, while the air it displaces returns through the equalisation line.

  2. 2. IsolateAt the upper trip point, the inlet valve and equalisation line close. The full chamber is sealed from your vacuum system, and new liquid waits above the closed inlet valve.

  3. 3. VentThe vent opens and atmospheric air enters the small air space. The chamber reaches atmospheric pressure within a fraction of a second.

  4. 4. DischargeThe outlet valve opens and the liquid drains under its own weight to the tundish or collection container, with vent air taking its place.

  5. 5. ResetAt the lower trip point, the outlet valve and vent close, the pump draws the chamber back to system vacuum and the inlet valve reopens. A 0.1 L chamber at 100 mbar admits 1.0 L of air at system pressure.

Figures for a system at 100 mbar absolute.

Get the full details

Our brochure covers it in detail, and our questionnaire tells us what we need to recommend the right one for your plant.

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