THB Auto Moisture / Water Float Bowl Drain Valve 1/2" NPT Inlet Compressed Air

THB D704NA Automatic Float Bowl Drain Assembly – 1/2" NPT | 175 PSI Max Working Pressure

Keep your compressed air system operating efficiently with this universal THB D704NA Automatic Float Bowl Drain Assembly. Designed to automatically remove accumulated condensate from compressed air systems, this heavy-duty drain helps prevent water buildup without requiring manual draining.

Unlike standard float drains, the D704NA features a durable all-aluminum enclosed bowl housing that protects the internal float mechanism while incorporating a built-in pre-screen filter. This screen helps prevent debris and contaminants from entering the float valve, reducing seal contamination and extending the service life of the internal drain.

The clear sight glass allows you to easily monitor condensate levels, while the integrated pressure relief valve provides a safe and convenient way to relieve system pressure before servicing or cleaning the unit.

Features

• Genuine THB D704NA Automatic Float Bowl Drain Assembly
• Heavy-duty all-aluminum housing for long service life
• Built-in pre-screen filter helps protect the internal float valve from debris
• Clear sight glass for quick condensate level inspection
• Integrated pressure relief valve for safe maintenance
• Automatic operation—no electrical power required
• Replaceable THB D-51 internal float drain eliminates the need to replace the complete assembly
• 1/2" NPT top connection for universal installation
• Maximum operating pressure: 175 PSI
• Accepts a 3/8" ID drain hose on the outlet nipple for directing condensate to a suitable drain location

Universal Compressed Air Applications

The THB D704NA is designed for use anywhere condensate collects within a compressed air system, including:

• Compressed air moisture filters
• Air receiver/storage tanks
• Air line drip legs and moisture collection drops
• Refrigerated compressed air dryers
• Aftercoolers
• General compressed air equipment
• Other industrial pneumatic applications

Simply install the drain vertically beneath the point where moisture accumulates. As condensate collects inside the bowl, the internal float automatically opens the drain valve once approximately 3 ounces of liquid have accumulated, then closes after the bowl has emptied.

Serviceable Design

Inside the bowl is the replaceable THB D-51 automatic float drain valve. Because only the internal float assembly typically wears over time, the D-51 can be replaced independently, saving the cost of replacing the entire bowl assembly.

In most compressed air systems, float drain valves should be inspected regularly and commonly require replacement every 1–2 years, depending on system contamination, oil carryover, and condensate quality.

Specifications

• Model: THB D704NA
• Internal Float Valve: THB D-51 (Replaceable)
• Connection: 1/2" NPT Female (Note: 1/2" NPT measures about 3/4" in diameter for reference)
• Maximum Working Pressure: 175 PSI
• Overall Height: 7.4"
• Overall Diameter: 3.2"
• Housing Material: Aluminum
• Sight Glass: Clear inspection window
• Drain Outlet: Fits 3/8" ID hose
• Operation: Automatic mechanical float drain (no electricity required)

The THB D704NA provides a reliable, maintenance-friendly solution for automatically removing condensate from virtually any compressed air system while protecting the internal drain mechanism from contamination and reducing routine maintenance.