A Problem You’ve Already Faced
- The receiver loses pressure in standby — the gauge drops visibly over 10–20 minutes with no air demand: the valve is not sealing in the closed position.
- The compressor strains and starts hard — the worn valve lets air back from the receiver into the block, forcing the motor to start against back-pressure.
- Hissing from under the pressure switch immediately after stopping — the М10×1.0 unloading port is not sealing: air escapes past the unloading line.
- Bought a “similar” valve — it didn’t fit — ordered 1/2″×16 mm instead of 19 mm, or 3/4″ instead of 1/2″.
Replacing the valve in time eliminates hard starting, stops receiver pressure loss and extends motor and piston group service life.
Technical Specifications
| Parameter | Value |
|---|---|
| Thread into receiver | 1/2″ male (BSP, ≈21 mm) |
| Block discharge tube inlet | 19 mm (compression or barbed fitting) |
| Unloading port | М10×1.0 (for pressure switch) |
| Body material | High-quality brass |
| Maximum pressure | 10 bar |
| Power compatibility | 2.2–3 kW |
| Construction | Serviceable |
Compatible Compressors
| Model | Block | Power | Compatibility |
|---|---|---|---|
| Remeza СБ4/С-50 LB30 | LB30 | 2.2 kW | ✅ |
| Remeza СБ4/С-100 LB30A | LB30A | 2.2 kW | ✅ |
| MZB V-0.25/8 | — | 2.2 kW | ✅ |
| MZB FL-40 | — | 1.5 kW | ✅ |
| Equivalents up to 3 kW with 1/2″ thread | — | up to 3 kW | ✅ verify dimensions |
💡 Expert tip: when replacing the valve, inspect the 19 mm discharge tube at the same time — cracks or worn seals will immediately cancel the new valve’s seal. Tightening torque for 1/2″ into the receiver: 25–35 N·m. Apply 2–3 wraps of PTFE tape to the thread — G (parallel BSP) thread does not self-seal.
How to Diagnose a Faulty Valve
- Stop the compressor with the receiver at working pressure.
- After 10–15 minutes check the gauge — a drop of more than 0.5 bar with no air demand indicates a faulty valve or worn tube connections.
- Apply soapy solution to the threaded joint and the tube barb — bubbles show the exact leak point.
Expert Opinion
“The check valve is a wear item you replace on symptom, not on schedule. Two main symptoms: the compressor starts with difficulty and the receiver slowly loses pressure in standby. If either is present — start with the valve: it is the cheapest and fastest diagnosis. On LB30/LB30A blocks the replacement takes 15 minutes.”
Vitali Bolucevschi, Chief Engineer at Acvatron SRL, 15 years in the industry
FAQ
❓ What is the difference between the 1/2″×19 mm and 1/2″×1/2″ valve?
The 1/2″×19 mm valve has a 1/2″ male thread on one end (screws into the receiver) and a 19 mm barbed tail on the other for the block discharge tube. The 1/2″×1/2″ valve has threads on both ends — used when both sides connect via threaded fittings with no barbed tail.
❓ Can a 1/2″×16 mm valve be fitted instead of 1/2″×19 mm?
No — the tail diameter must match the inside diameter of the discharge tube. A 19 mm tube will not stay on a 16 mm tail — it will leak under pressure. Measure the tube ID with a calliper before ordering.
❓ Is PTFE tape required when fitting?
Yes. The 1/2″ BSP thread is parallel (G) — it does not self-seal. Apply 2–3 wraps of PTFE tape in the thread direction before fitting. Tightening torque: 25–35 N·m — do not over-tighten, the body is brass.
