Castair WV99

The Castair WV99 is an air-operated automatic drain valve designed for piston air compressors in the 1-10 HP range. It mounts directly on the tank drain port and uses a small pilot air signal to open and expel accumulated condensate on a timed cycle. No electricity, no manual draining, no forgetting. If your shop has a compressor that sees regular use, the water that collects in the tank overnight is the thing quietly rusting it from the inside out. The WV99 deals with that automatically. What It Does and Why It Matters Every piston air compressor generates condensate. Ambient air contains moisture, and when that air is compressed and cooled in the tank, water drops out. In a shop running tools regularly — air ratchets, impact guns, spray guns, blow guns — that moisture accumulates fast. Left unchecked, it: Rusts the tank from the inside, shortening its service life Sends water downstream into your air lines, tools, and painting equipment Forces you to manually drain the tank — a task that gets skipped The WV99 eliminates the manual step. It is an air-operated valve: a small pulse of compressed air triggers it to open, expel water, and close. Castair lists it specifically for 1-10 HP compressors, which covers most garage and light commercial units — the 5 HP commercial series units like the C513HA8 and C516VA8, the garage series G-models, and portable units. How Air-Operated Drain Valves Work An air-operated drain valve uses the compressor's own output air as the trigger. A timer or pilot signal sends a brief pulse to the valve, which opens the drain port long enough to expel water, then closes. No solenoid, no 120V wiring. This makes it simpler to install and eliminates one more electrical component to fail. The WV99 is the valve only — no timer, no pilot circuit included. It requires a compatible pilot or timer signal to operate. Castair sells complementary components in the same automatic drain family: WV99 — Air-operated valve only, 1-10 HP (this part) ADVS — Air-operated valve only (alternate model, also for 1-10 HP) ADVSM — Air-operated valve with installation kit, 1-10 HP IVS04 — Strainer with shut-off, all models (recommended upstream of any auto drain) SDV03S — Electronic drain with strainer, 115V, all HP ranges SDV03M — Electronic drain with installation kit, all HP ranges PC14 — Petcock 1/4", manual drain, all models AFD1 — Watts bowl float drain, for filter housings AFD3 — THB bowl float drain, for filter housings BPS — Replacement screen for IVS04 strainer Installation Considerations The WV99 threads into the tank's bottom drain port. Before installing any automatic drain valve, Castair recommends adding the IVS04 strainer with shut-off upstream. The strainer catches any tank scale or debris that could plug the valve seat — a plugged drain valve is worse than no drain valve at all, because it gives you false confidence while doing nothing. For a complete, ready-to-run installation, look at the ADVSM — same valve with the mounting hardware and fittings included. The WV99 alone is the right choice if you already have the installation hardware or are replacing an existing valve. What's in the Box 1x Castair WV99 air-operated automatic drain valve Installation hardware, strainer, and pilot/timer components are sold separately. Contact us to spec out the complete installation for your compressor model. When Does a Shop Need This vs. Stepping Up or Down The WV99 is rated for 1-10 HP compressors. That covers: Castair Garage Series: G15115VP30, G212P50, G3516VS75 Castair Commercial Series (5 HP units): C513HA8, C516VA8, C518VA8, C518HA8, C518VC1, C518HC1 Castair portable and contractor units in the same HP range If you have a 10 HP or larger commercial or industrial compressor — the Castair C2 (7.5-10 HP), C3 (10-15 HP), or duplex units — move up to the SDV03S or SDV03M electronic drain, which handles larger CFM volumes and all HP ranges. The air-operated WV99 is sized for smaller displacement pumps where a simpler, non-electric solution makes sense. If you're on a tight budget and don't mind a manual routine, the PC14 petcock is the lowest-cost option. But a petcock only works if someone actually opens it every day. In a busy shop, that doesn't happen. The WV99 removes the human variable. Castair Automatic Drain Product Line — At a Glance WV99 — Air-operated valve only, 1-10 HP ADVS — Air-operated valve only, 1-10 HP (alternate) ADVSM — Air-operated with install kit, 1-10 HP IVS04 — Strainer with shut-off, all models (add this upstream) SDV03S — Electronic drain with strainer, 115V, all HP SDV03M — Electronic drain with install kit, all HP PC14 — Manual petcock, 1/4", all models Technical Specifications Part Number: WV99 Type: Air-operated automatic drain valve (valve only, no timer included) HP Range: 1-10 HP piston compressors Operation: Pilot air-actuated Application: Tank drain, drip legs, filter housings Manufacturer: Castair Note: Manufacturer specifications for thread size, port dimensions, and maximum PSI rating are not published on Castair's website — contact us for complete specs before ordering if your installation has specific requirements Why Buy From Air Compressor Factory Direct? We have stocked and sold Castair compressors and service parts since 2016. The WV99 is one of those parts that's easy to find the wrong version of — there are multiple auto drain configurations in the Castair lineup, and picking the wrong valve for your HP range or installation type wastes time and money. Call us before you order if you have questions about which drain valve is right for your specific unit. We'll look it up by model number and tell you exactly what you need. Free shipping on all orders. Free tech support before and after the sale. If the WV99 arrives and it's not the right fit, we'll get you to the right part. Call 866-217-0063 for quick answers and help!