I have to do abet of work to do on a house that has lead coming in to a gate valve then an iso valve. The owner doesn't want to replace in mdpe. From boundary stop tap at the moment. So to isolate the houses water supply I have the iso valve or the boundary stop tap in the road. As the gate valve goes no were near turning off mains pressure. Which would you suggest turning of the iso valve and hope it doesn't leak out of the slotted part or the boundary stop tap. Key require to access. I will try upload a picture of under the sink its not the worlds best plumbing by any stretch of the imagination. Probably the worse layout I've seen in my limited experience.