Sometimes a little water will continue to flow after a gate valve is closed as fully as possible. In some cases the plumbing repairs inside the property can be performed with a little bit of water flowing through the system. But there is an other option as well. If there is a slight flow of water the easiest solution is to jump the valve.
Jumping a valve simply means to leave the defective valve in place and simply install a brand new valve after it. If legal for your area and for your type of water service line the preferred valve to use is a ball type valve. A full port ball valve allows for full flow of water, is rated higher than most gate valves, is longer lasting, and is not prone to break.
If you choose to install a second main control valve it is a good idea to remove the handle on the original valve or label it as a reminder so it is not used in the future. The last thing you would want to do is to use an old defective valve in the future and have it break in the closed position.