A gate valve for a property usually has to be closed if plumbing repairs or maintenance are needed inside the building. In some instances, particularly if the main control valve is a gate type valve, the valve may not close completely. In many cases a gate valve repair may be needed. But many times other remedies are available.
A gate valve not closing completely is typically due to sediment that has built up inside the body of the valve. The sediment becomes lodged between the gate that lowers, and the inside of the valve body itself. Ball type valves do not suffer from this problem, as they operate on a different principal than a gate that raises and lowers inside of the valve body.
The typical reaction when a gate valve will not close fully is to exert addition force on the handle. Using force to close a valve is absolutely the wrong response. Brute force can cause permanent damage to the valve and a loss of water supply to the building. If sediment or mineral deposits are preventing the gate valve from closing fully, there is a more sensible first step to take than brute force.
If sediment or mineral deposits are preventing a gate from closing completely an attempt should be made to flush out the inside of the valve. The proper way to do this is to open a faucet on a sink inside the house so there is a flow of water. Then gently and repeatedly open and close the valve.
If the handle of the valve does not turn freely then loosen the packing nut just above the valve body and around the stem of the valve. Loosening it just one turn should be fine – just remember to tighten it back up when you are done. Every time you lower the gate some sediment will break free and be flushed away by the water flow. There is absolutely no harm or danger in how many times you do this as long as no excessive force is used.
Routinely opening and closing a gate valve helps it to last longer than if it is left frozen in place for long periods of time. This is called exercising the valve. Experienced building managers make this chore a part of their standard maintenance duties.