If the main stop cock valve in your property is leaking it should take very little time to remedy. It is highly likely that these valves will fail to work at some point in their lives, as they are really not operated much for years so debris will build up on the inside. It might be that there is no choice to replace the valve. But, you may want to try a repair first to see if it can be saved. A Lewisham Plumber is a qualified professional. For information, the stopcock in most properties is the main isolator for the water supply into your property and are normally found under sinks or stairs. For the valve to leak it means that water is getting past the gland nut. The first thing to do is to try and re-tighten the gland nut by turning clockwise action. When the nut is tightened it pressurises the packing inside giving a seal, but this makes the valve really stiff to turn. Lewisham Plumbers can repair leaks on all types of valve. The best remedy for this is to re-pack the valve gland. The material is available at all plumbing outlets. You should only attempt this job if you are confident. Here is a guide to re-packing: Shut off the valve to be repacked. Undo the gland nut by turning anti-clockwise until it comes away from its housing so it can be slipped further along the spindle. There may be some water but this will drain away. Having taken off the gland nut, wrap some PTFE tape around the spindle and push it into the void that the packing gland nut screws. Use a small screwdriver to poke it down. Replace the nut and tighten enough to squeeze the new material in the gland. Open up the valve and tighten the gland nut until any water that is still coming through stops. “