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A leak or a leak is a hole or a leakage in a product or in technical systems through which solids , liquids or gases undesirably enter or exit can. A leak can lead to the failure of an entire technical system. The leak rate is a measure of the size of a leak .

Relationship between hole size and leakage rate

In the technical sense, tightness only means "free of leakages according to the technical area of ​​application". On closer inspection, the requirements placed on technical systems are very different.

The following rough estimates apply to the relationship between the hole size and the associated leakage rate:

Hole diameter Leak rate in
mbar × l / s
General leakage description
(∆p = 10 5  Pa)
Gas leak description
(∆p = 10 5  Pa)
≈ 1 mm 10 2 water is leaking out
≈ 300 µm 10 1
≈ 100 µm 10 0 Dripping faucet ≈ 1 cm³ gas loss per second
≈ 30 µm 10 −1 ≈ 1 cm³ gas loss in 10 seconds
≈ 10 µm 10 −2 waterproof (does not drip) ≈ 1 cm³ gas loss in 100 seconds
≈ 3 μm 10 −3 vapor-proof (sweating) ≈ 1 cm³ gas loss in 15 minutes
(approx. 1 gas bubble per second)
≈ 1 μm 10 −4 bacteria-proof ≈ 1 cm³ gas loss in 3 hours
≈ 300 nm 10 −5 petrol and oil tight ≈ 1 cm³ gas loss per day
≈ 100 nm 10 −6 virus-proof ≈ 1 cm³ gas loss in 10 days
≈ 30 nm 10 −7 gastight ≈ 1 cm³ gas loss in 100 days
≈ 10 nm 10 −8 virus-proof (secured) ≈ 1 cm³ gas loss in 3 years
≈ 3 nm 10 −9 gastight (secured) ≈ 1 cm³ gas loss in 30 years
≈ 1 nm 10 -10 absolutely tight (technical) ≈ 1 cm³ gas loss in 300 years
≈ 0.3 nm 10 −11 ≈ 1 cm³ gas loss in 3000 years

Types of leaks

Leakages are divided into the following groups according to the type of characteristic :

  • Hole leakage (clearly visible)
  • Turbulent leakage (whistling gas leakage)
  • Laminar leakage (leakage in detachable or non-detachable connections such as in flanges, weld seams, etc.)
  • Molecular leakage (also pore leakage; leakage caused by the finest pores or damage in the polycrystalline structure of a material)
  • Virtual leakage (apparent leakage caused by the evaporation of liquids or by outgassing)
  • Cold / warm leaks (reversible leaks that only occur under extreme temperature loads)
  • Valve leakage or flap leakage (leakage with preferred flow direction)
  • Lambda leakage (leakage that occurs when helium is liquefied)

The material-specific gas permeability ( permeation ) of a material is not a leak in the classic sense .

Ship leak

Leaked and sagged museum ship Seute Deern in Bremerhaven

A leak (hole) in a ship leads to the penetration of water into the ship's interior ( leakage water ). In the event of a leak below the water line, the water penetrates through the water pressure acting from the outside. If the ship is heeled , a leak can also lead to water ingress above the waterline by submerging below the water level. Water can penetrate through open or smashed hatches or windows or through leaks on the ship's side ("water ingress"). Heavy rain and waves can also cause greater water ingress, depending on the location of the leak.

The penetrating water can affect the stability of the ship or cause it to sink .

Leakage current

The leakage flow (the amount of inflowing water per unit of time) is measured in liters / minute or cubic meters / hour.

The following are decisive for the leakage current:

Diameter of the leak
Depth of the leak below the surface of the water
Shape of the leak (constriction number)

The leakage current is greater, the deeper the leak is below the water level, the greater the leakage diameter and the greater the number of constrictions (the more rounded the inlet in the longitudinal section and the rounder and smoother the hole cross section; maximum 1). The buoyancy of the ship and the leakage current can be used to calculate how long a ship will theoretically continue to swim (if it does not capsize beforehand).


Causes can be:

Grounding or running aground
Collision with floating debris, other ships, whales, port facilities, etc.
Stress cracks
after a mast or rudder break
to the stuffing box, stern tube, sea cock, rudder trunk etc.
defective hoses and valves (toilet)

Leak control

With small leaks the penetrated water can with a bilge pump pumped or with a Lenz bucket or bailer be scooped out. It is crucial that the inflow volume is as small as possible than the pump output. Even if the pumping power is smaller, it delays the net leakage current and increases the time available for leak detection and sealing. An effective measure is to heel the ship so that the leak is as high as possible, ideally above the water level. In the case of small leaks, it is also effective to immediately seal the hole with a body part by pressing against it.

Inside, large ships are divided into watertight chambers by locks. If the locks of the damaged chamber are closed, the ship can still be maneuverable even with the chamber flooded.

The aim of any leak control is to close the leak as permanently as possible, for example by pressing a plate against it and wedging it with wooden or metal supports. The Fizzical had to serve to test various methods of leak control under realistic conditions.

Leak on the dinghy

If a rubber dinghy leaks, only air escapes from one chamber for the time being. It only sinks when the remaining buoyancy of all chambers and the hollow space they still span is less than the dead weight of the boat plus cargo.

Leak in pneumatic tires

Leaks in pneumatic tires (with or without inner tube) can behave very differently. A stuck foreign body can seal the leak at rest or for a certain distance. Small leaks can close almost completely if the pressure has dropped sufficiently. A leak can be glued from the inside with a special sealing liquid or, in the case of tubular tires, repaired with a patch on the tube .

Leak size

The Hazardous Incident Ordinance defines defined and undefined leak sizes.

Defined leak sizes

Emissions via the following defined leak sizes:

Undefined leak sizes

See also

In the sense that under a leak one generally sees an unwanted escape of something, which one cannot get hold of again, there is also the term memory leak in computer science .

If data and information, for example about people, companies, products etc. are passed on in an unauthorized manner or if such information is stolen, this is often described with the term data leak .


  • Max Wutz: Theory and Practice of Vacuum Technology. 3rd, revised and expanded edition. Edited and edited by Wilhelm Walcher and Hermann Adam. Vieweg, Braunschweig a. a. 1986, ISBN 3-528-14884-5 .

Web links

Wiktionary: leak  - explanations of meanings, word origins, synonyms, translations