Gate valve in the airing cupboard for the CW isn't closing fully. I was going to remove the old valve and replace it with a ball lever valve, but if I remove the old one and cut the pipe just above the old olives, there may not be enough pipe to fit the replacement. So, is it perfectly fine to install the new valve above the old gate vslve, leaving the gate valve in situ. I could just remove the knob from the gate valve to decommission it. Would be a safer option for the install.