The Purpose of Drain Valves

Water vapour is a byproduct of operating either a rotary screw or reciprocating air compressor. The vapour condenses into liquid and falls to the bottom of the air tank. A drain valve helps to remove the accumulated water before it causes significant damage to the compressor that requires extensive repairs or replacement.

What Is the Drain Valve?

A condensate drain valve is a small device typically located at the bottom of a compressor’s air receiver. Whether the air compressor drain valve is open or closed determines if water flows out of or remains inside the compressor air tank.
While the reservoir tank is the typical drain valve installation point, it can also help remove moisture from other compressor components and related products. You can use an air compressor valve extension with compressor filters, air dryers, drip legs, air/water separators and virtually anywhere else condensate is an issue.

What is the Purpose of a Drain Valve?

In its natural state, air can hold a substantial amount of water vapour. The function of creating compressed air significantly reduces the vapour-holding capacity. The compression process forces water molecules to clump together and form condensation. The effect is similar to a rainstorm inside the tank.

A drain valve performs the critical function of allowing excess water vapour to escape into the atmosphere. The removal of condensation helps prevent the formation of corrosion that will eventually damage the compressor and shorten its lifespan. By eliminating water from the compressed air system, the drain valve also reduces wear on tools and equipment powered by the compressor unit.

Types of Drain Valves

Examples of the many types of air compressor drain valves include:

Float-operated: This valve allows water to flow into a special housing. When the water inside the tank reaches a predetermined level, a float triggers the drain’s opening and lets the excess water drain out.

Timer-controlled: A timer-controlled valve opens and closes at pre-set intervals. This type of system is ideal for highly regulated operating environments.

Zero-loss: This type of drain valve contains a sensor probe that monitors water accumulation inside the tank. When the water reaches a specified level, the probe delivers an electrical signal to a solenoid. The drain then opens, but the water flow stops before the release of compressed air.

How to Use a Drain Valve?
Each of the drain valve types listed above operates automatically, meaning little or no manual intervention is necessary. The biggest challenge is to choose a model that is compatible with your equipment and meets your operating requirements.

For example, a float-operated unit makes sense if your compressor is not near an electrical source. A timer-controlled version is likely the best option if you operate your compressor on a regular schedule. A zero-loss air compressor drain valve works well if you are concerned about minimizing the loss of compressed air during draining.