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Wet vs dry leak detectors

November 1, 2021


From government labs to classified defense operations, today's manufacturing world involves many advanced processes. Some of these require that their systems be pressurized or depressurized to exact specifications in order for them to succeed - and when they do, leak detection systems become essential.

There are several leak detector configurations and testing modes, but to choose the right one, it's important to know the difference between the two primary types: wet and dry. We'll take a look at both and help you decide which works best for your application.

What is a leak detector?

As their name implies, leak detectors are used to measure fluid or gas leakage in either pressurized or evacuated systems or find the exact location of a leak in a component.

The fundamentals of leak detection involve many details, but in its most basic form, leak detectors are a form of non-destructive testing (NDT) that measures the amount of air escaping from a machine or industrial process. It works by detecting the partial pressure of helium inside the suction tubing of a vacuum pump. The type of leak detector (Wet or Dry) you should use depends heavily upon the application.


There are many applications that require a pressurized or vacuum system, which means that leak detectors are used in a wide variety of industries today. Some of the most common leak detector applications include:

  • Medical device manufacturing
  • Laboratories and pharmaceutical manufacturing
  • Manufacturing processes
  • Aerospace
  • R&D
  • Semiconductors
  • Food-grade materials
  • Particle accelerators
  • Defense
  • Optics

In general, any environment that requires pressurization or depressurization will need a leak detector to make sure its system remains stable.

Wet or dry?

While other factors must certainly be considered, the application should be the chief parameter when choosing a leak detection system. Wet systems employ oil within their vacuum pump, so some small amount of oil vapors may be emitted during their use. Dry leak detectors use no oil, and therefore are emissions-free. If your application requires that no oil vapors be emitted, it is very likely that you should use a dry leak detector.

Although it's often the primary determining factor, the application isn't the only thing you should consider when choosing a leak detecting system. Here are some other differences between the two. 


Unless a Wet leak detector is used very infrequently, maintenance is recommended once a year. Typical yearly maintenance includes oil and filter changes and cleaning. Signs of needing maintenance include oil color, oil smell, and high background levels. The newer leak detectors include maintenance counters which automatically alert the operator when it’s time for maintenance.  

Because no oil is used in the vacuum pump, dry leak detection systems do not need to be maintained as often. Most dry leak detectors only need the vacuum pump maintained every two years, with rotary lobe vacuum pump models lasting up to four years in between maintenance cycles.


Wet and Dry leak detectors are both very robust and reliable devices, and you can reasonably expect both to last up to 10 years in clean applications. Dry systems are a little easier to maintain without the necessary oil changes and disposal. Both Wet and Dry leak detectors include air cooling filters to protect the electronics that must be maintained based on usage.


Matching their toughness, wet and dry leak detectors are both designed with simplicity in mind. Employing the same software, they function nearly identically, with the only difference being the helium leak rate tightness of the dry vacuum pump models. Both systems also are capable of all four testing methods: external vacuum, internal vacuum, over-pressure vacuum, and sniff test.


Because they are designed relatively similarly, there is little difference between the price of a wet and dry leak detector. Dry systems cost 3–5% more than their wet counterparts, but the savings from less maintenance has the potential to offset some of the added expense.

Leybold: leading the way in leak detection

As with any device, customer service is also an essential part of choosing a provider. Leybold not only uses its industry expertise to engineer some of the most high-performing leak detection systems the market has to offer, but we take your satisfaction seriously, too. Our remote service system enables our team of experts to deliver the support you need, and our models are built to endure the environments in which they must perform.

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