Most common causes:
- Worn seats or seals. PTFE seats degrade over time, especially with abrasive fluids or high cycle frequency. A scratched seat no longer seals properly.
- Internal debris. Rust, sand, or scale can get trapped between the ball and seat, preventing full closure.
- Incorrect installation. Over- or under-tightening, impact during assembly, misaligned fittings.
- Corrosion or chemical attack. Material not compatible with the fluid or installation environment.
- Thermal stress. Extreme temperatures deform seats; freezing can crack the valve body.
Where is the leak coming from?
Near the handle → stem or O-ring.
From the body or fittings → threads or bolts.
Valve closed but fluid passing through → damaged internal seats.
How to fix it
Slightly tighten the packing nut for stem leaks. Operate the valve several times to dislodge debris. If the problem persists, replace seats and seals with an original kit. For non-repairable valves, full replacement is the fastest solution.
Prevention is better than repair
Operate the valve periodically, check for moisture signs, and always choose materials compatible with the fluid. A small ignored drip can turn into a costly failure.