In my bath/shower I've had a new mixer tap fitted that has a bar valve (when the tap is running you lift the valve to make the water come out of the shower head. When you turn the tap off, the valve falls back down so that the water will come out of the tap again.)
My valve is a sticky and sometimes it's very hard to lift it. When I do lift it, it won't fall back down on its own and can be difficult to push down.
Is it safe to lubricate it?