How can you tell if a shut-off valve is faulty or leaking?

There are several ways to identify if a shut-off valve is faulty or leaking.
Visible Leaks Around the Valve:External leaks: If you see water or fluid dripping from around the valve stem, handle, or connections, this is a clear sign that the valve may be leaking. Leaks can occur from faulty seals, O-rings, or worn gaskets.Corrosion or stains: Rust, mineral deposits, or water stains around the valve could indicate a slow leak or past leakage.
Difficulty in Turning the Valve:Stiff or hard to operate: If the valve is difficult to turn, it might be due to corrosion, sediment buildup, or damage inside the valve mechanism.Loose handle: A handle that spins without engaging the valve mechanism properly can indicate internal failure or a broken component.
Unexplained Water Pressure Fluctuations:Low water pressure: A valve that is not fully closing could cause reduced flow or low water pressure in the system.Water hammer: If the valve does not close properly or is partially open, it may lead to water hammer (a sudden pressure surge) in pipes, causing banging noises.
Wet or Damp Surrounding Area:Puddles or dampness around the valve: If the area around the valve is consistently wet or damp, even when the valve is supposed to be closed, this suggests a slow leak or a fault in the valve’s seal.
Unusual Sounds:Hissing or dripping sounds: A faint hissing sound when the valve is supposed to be closed can indicate a slow leak through the valve. Similarly, you may hear a dripping sound from the valve’s body if there’s a leak inside.
Inability to Fully Close the Valve:Valve won’t shut off completely: If the valve doesn’t completely stop the flow of water or gas when it’s turned to the "off" position, the valve could be malfunctioning. This could be due to internal wear, sediment buildup, or a damaged seal.Water still flows: A shut-off valve that still allows water to flow even when fully turned off is a clear sign of a fault.
Vibration or Excessive Movement:Movement or shaking: If the valve wobbles or shakes when you try to operate it, it may indicate loose components, corrosion, or that the valve is improperly installed.
Changes in Temperature or Surface Condition:Hot or cold spots on the valve: If a hot water valve feels cooler than usual or a cold water valve feels warm, it may be leaking internally, causing temperature changes due to improper sealing.
Visible Wear or Damage:Cracked or broken body: A cracked or broken valve body will likely leak, so visual inspection is important to check for physical damage.Worn or damaged rubber seals: The rubber washers or seals inside the valve can wear down over time, leading to leakage.
Sudden Water Supply Problems:If there are problems with water supply or pressure that occur suddenly when operating a valve, such as water continuing to flow despite the valve being "off," or sporadic water flow when the valve is on, it could indicate a malfunctioning shut-off valve.