Castair Liquid-Filled Pressure Gauge — 1/4" NPT, 2.5" Dial, 0-300 PSI, Bottom Mount (*GL251430U)
The *GL251430U is a liquid-filled 2.5-inch pressure gauge with a 1/4" NPT bottom-mount connection and a 0-300 PSI range. This is the bottom-mount version of Castair's liquid-filled 2.5" gauge — where the *GL251430B mounts from the back, this gauge mounts from below, making it the right choice when the gauge is installed in-line on a pipe or when the fitting is positioned beneath the gauge body. The glycerin fill keeps the needle stable on a running compressor, dampening pulsation and vibration that would otherwise cause needle bounce and premature wear in a dry gauge.
Why a Liquid-Filled Gauge on a Compressor?
Piston compressors generate pressure pulses on every stroke. Without liquid fill, a gauge needle bounces with those pulses — making the gauge hard to read under load and wearing out the movement's pointer pivot and gear sector in a fraction of the time. Glycerin fill absorbs those pulses, holds the needle steady, and extends gauge service life substantially. On any compressor application with significant vibration or pulsation — and that includes virtually all piston compressors — liquid-fill is the right specification.
Gauge Specifications
- Fill: Liquid-filled (glycerin) — dampens pulsation and mechanical vibration for stable, readable needle position
- Connection: 1/4" NPT — standard thread for Castair compressor pressure ports and tank fittings
- Mount: Bottom mount — pipe enters from the bottom of the gauge body, face reads upward or outward. Use when the gauge is installed on a horizontal pipe run or in-line fitting below the gauge position.
- Dial Size: 2.5 inches — large enough to read at arm's length in a shop environment
- Range: 0-300 PSI — covers the full operating range of Castair compressors (95-175 PSI cut-out) with substantial headroom to the top of the scale
- Frame: Steel frame — durable construction for shop and industrial use
- Part Number: *GL251430U
Castair Gauge Lineup — Choosing the Right Mount and Fill
Castair offers dry and liquid-filled gauges in several sizes and mount configurations. The model number gives you the specs:
Dry Gauges
- G251430B — 1/4" NPT, 2.5" dial, 0-300 PSI, back mount (dry)
- G251430U — 1/4" NPT, 2.5" dial, 0-300 PSI, bottom mount (dry)
- G201420B / G201420U — 1/4" NPT, 2" dial, 0-200 PSI, back/bottom mount (dry)
Liquid-Filled Gauges (Pulsation/Vibration Applications)
- *GL251430B — 1/4" NPT, 2.5" liquid-filled, 0-300 PSI, back mount
- *GL251430U — THIS PRODUCT — 1/4" NPT, 2.5" liquid-filled, 0-300 PSI, bottom mount
Flanged Gauge
- GF251430B — 1/4" NPT, 2.5" flanged dial, 0-300 PSI, bottom mount
Bottom Mount vs. Back Mount — How to Tell Which One You Need
Look at the existing gauge on your compressor. If the pipe enters from below the gauge body, you have a bottom-mount gauge — order the *GL251430U. If the pipe enters from behind the gauge (gauge face is flush with a panel), you need the back-mount version — order the *GL251430B.
Bottom-mount gauges (*GL251430U) are common in in-line pipe installations and on tank fittings where the gauge protrudes upward. Back-mount gauges (*GL251430B) are typical on control panels and manifold plates.
What's in the Box
- 1 x Castair liquid-filled steel frame pressure gauge (*GL251430U)
- 1/4" NPT bottom-mount connection (male threads)
Technical Specifications
- Part Number: *GL251430U
- Connection Size: 1/4" NPT
- Mount: Bottom mount
- Dial Size: 2.5 inches
- Pressure Range: 0-300 PSI
- Fill: Liquid-filled
- Frame: Steel
- Application: Castair piston and rotary screw compressors, air receivers, pressure manifolds
Why Buy From Air Compressor Factory Direct?
We have supplied genuine Castair parts and accessories since 2016. Matching the correct gauge to your compressor requires knowing the mount type, fill type, dial size, and pressure range — get it wrong and you either cannot make it fit or it reads inaccurately. We carry the complete Castair gauge line and can confirm the right part for your specific unit. Free shipping, free tech support at 866-217-0063, full manufacturer warranty.
Call 866-217-0063 for quick answers and help!
