Loose bathroom sink handle

[Laprairie]

Looking for some DIY help. One of the handles of my bathroom sink is loose. When I turn it open and shut, it does not shut off, instead the join between valve between the handle and the lower pipe turns and become loose. Also I am not familiar with the T-shaped join, I asked my local hardware store owner and he's never seen it before.

Also, I'm having trouble taking off the handle. There is no access for an Allen key and it also doesn't seem to pop off easily, I also tried to turn the base counterclockwise but it doesn't seem to budge. Do I need to take off the handle to fix this problem?

Any advice would be appreciated.

 

[Twowaxhack]

It’s made by “ Phister “

The tee comes off by pulling the grey ring evening down and it’ll slide off. It’s a pushfit fitting similar to a sharkbite fitting.

 

[GReynolds929]

Basin wrench will tighten the handle mounting nut under the counter. Handle comes off by turning the bell counter clockwise.

 

[Laprairie]

Thanks! Now that I know what the brand is, I looked it up and it appears that the handle becoming stuck to the base is a common issue, which is why the handle is not coming off easily.