What are condensate drains used for in industrial installations?
Condensate drains — also known as drain valves or auto drain valves — remove the condensate that naturally builds up in compressed air systems, discharging accumulated water and oil from filter bowls, air dryers and receiver tanks without operator intervention. Left untreated, this condensate can corrode piping, damage downstream components and contaminate the process, so reliably removing it is a basic requirement for any compressed air installation.
A condensate drain provides an automatic way to remove this accumulated moisture from compressed air equipment. SMC’s float-operated drain valves use mechanical operation to discharge condensate without requiring an electrical power supply.
In automated systems, automatic condensate drains reduce the manual checks and bowl-emptying rounds that condensate would otherwise require, supporting more efficient day-to-day industrial maintenance.
SMC’s range covers float-operated valves that discharge automatically with no electric power at all, together with heavy-duty options designed for higher condensate discharge requirements. Explore our digital catalogue to find the drain valve or condensate drain that best suits your application and keeps your compressed air system clean and reliable.
Why choose SMC drain valves?
SMC offers a focused range of robust auto drain valves designed to keep condensate under control without adding complexity to your system.
Our condensate drain solutions combine:
- Fully automatic float operation, with no electric power required
- Tool-free bowl mounting and removal on selected options
- A manual drain cock for on-demand discharge on selected drain valves
- Bowl materials suited to demanding environments, including polycarbonate, nylon and metal options
- Heavy-duty options for higher condensate discharge requirements
- Maintenance options that allow servicing without changing existing piping.
Selected drain valves require only 30 mm of space underneath for maintenance and allow the bowl to be removed without tools. Other heavy-duty options have been designed so maintenance can be carried out without changing the existing piping.
Whether you need a compact condensate drain for a compressed air installation or a heavy-duty drain valve for a more demanding application, SMC provides reliable condensate management without requiring electrical power for its float-operated options.
SMC condensate drain and drain valve range
SMC’s auto drain valves are designed to discharge condensate automatically as it accumulates, protecting your compressed air system without operator intervention.
The range includes:
Both are a standard part of many air treatment set-ups, working alongside filters, regulators and air dryers to keep the system properly drained.
Typical applications for SMC auto drain valves include:
- Automatic condensate discharge from filter and filter-regulator bowls
- Draining air dryers and receiver tanks
- High-flow lines where manual draining would be impractical
- Applications with higher condensate discharge requirements
- Retrofitting or maintaining condensate drainage with minimal piping changes, depending on the selected option
- Systems where avoiding electrical wiring for drainage is a priority.
Key features of SMC auto drain valves include:
- Float-operated automatic discharge, with no electric power required
- One-touch bowl mounting and removal on selected drain valve options
- Manual drain cock for on-demand discharge on selected drain valves
- Operating pressure ranges suited to different compressed air applications
- Bowl guard and bowl materials suited to demanding environments
- Heavy-duty condensate drain options for higher discharge requirements.
How SMC drain valves improve your industrial process
SMC’s auto drain valves bring clear advantages to industrial operations.
- Less manual intervention: Automatic float operation reduces the need for scheduled manual draining when the condensate drain is operating within its specified conditions
- No wasted compressed air: Float operation only opens when condensate is present, helping avoid continuous air loss from a drain left cracked open, supporting your energy efficiency goals
- Reduced corrosion risk: Regular condensate discharge protects piping, valves and downstream components
- Simple retrofitting: Selected condensate drain options can be maintained without changing existing piping
- No power supply needed: Fully mechanical, float-operated models run without electrical wiring or controls
- Built for demanding duty: Heavy-duty condensate drains are available for applications with higher condensate discharge requirements, forming part of SMC’s high durability solutions.
How to select the right condensate drain
Choosing the right condensate drain depends on several key factors:
- Condensate volume: Consider whether the application requires standard drainage or a heavy-duty option for higher condensate volumes.
- Discharge capacity: Selected SMC drain valves can provide up to 100 cm³ per cycle, while heavy-duty options can discharge up to 400 cc/min at 0.7 MPa when draining water. These capacities are specified using different measurement formats and should not be treated as a direct like-for-like comparison.
- Mounting: Consider whether the condensate drain needs to fit into the existing installation with minimal changes. Selected SMC options are designed for simplified maintenance, including tool-free bowl removal or maintenance without changing existing piping, depending on the product type.
- Bowl material: Polycarbonate, nylon and metal options are available depending on the operating environment. Where substances that may affect resin materials are present, we recommend using a metal bowl when material compatibility is in doubt.
- Operating pressure and flow: Match the condensate drain valve to the pressure conditions of the compressed air system. SMC options cover different operating pressure ranges, including 0.1 to 1.0 MPa for selected normally open drains, 0.15 to 1.0 MPa for selected normally closed drains and up to 1.6 MPa for heavy-duty options.
- Compressor capacity: Some normally open float-operated drains require a compressor discharge flow of 400 l/min (ANR) or more. Where compressor capacity is lower, SMC recommends a normally closed option to help avoid continuous air discharge during start-up. Heavy-duty options require an air compressor discharge flow higher than 50 l/min (ANR).
- Maintenance access: Consider the available installation space and how the drain will be serviced. Selected products require only 30 mm of clearance underneath, while heavy-duty options are designed for maintenance without modifying existing piping.
To make selection easier when specifying a full air-preparation line, use our Airline Equipment Configurator, available within the Engineering Tools section of our website.
Need help selecting the right condensate drain?
If you’re unsure which drain valve best fits your application, contact our technical specialists to get help to evaluate your operating pressure, compressor capacity, condensate requirements, installation conditions and maintenance needs and recommend the appropriate solution.
Frequently Asked Questions about drain valves
What is a condensate drain in a compressed air system?
A condensate drain removes liquid that accumulates inside compressed air equipment. An automatic condensate drain uses a mechanism such as a float to discharge this condensate automatically rather than relying on an operator to open the drain manually. SMC’s float-operated drains do not require electrical power for automatic discharge.
What’s the difference between an auto drain valve and a manual drain valve?
A manual drain valve has to be opened by an operator to release condensate, which depends on regular checks being carried out. An auto drain valve discharges condensate automatically as it accumulates. Selected SMC condensate drains also include manual discharge for on-demand draining when required.
Do SMC auto drain valves need an electrical power supply?
No. The float-operated condensate drains in this range discharge automatically without electric power or electrical wiring.
How much condensate can SMC condensate drains discharge?
Depending on the type, selected SMC condensate drains can provide up to 100 cm³ per cycle, while heavy-duty options can discharge up to 400 cc/min at 0.7 MPa when draining water. These values are specified using different measurement formats and should not be treated as a direct capacity comparison.
Do auto drain valves waste compressed air when they operate?
SMC heavy-duty float-operated drains provide automatic discharge without wasting air. Correct operating pressure and compressor capacity must still be respected for proper operation.
For normally open float-operated drains, correct selection is important because insufficient compressor capacity can cause continuous air discharge from the drain during start-up.
