Plaster in PVC pipe - ideas to remove

[Scott-Texas]

Following a plaster job, I was left with a plaster blockage in the bottom of the spa drain pipe. Looking for ideas on how to remove. It is where the two drains meet and then form a tee, leading back to the pump. It is hard to get at as it is about 1 foot in from the drain basket, and then at 90 degrees where the second pipe carries water away. I used a small camera in the pipe to take a picture. Acid has not worked. Scraping it with a metal hook has not worked. It is pretty solid and attached to the PVC (I.e. not a chunk that's just stuck). Running out of ideas. Thanks!

 

[Pool_Medic]

A dremel with grout removal tool will work.

 

[Scott-Texas]

A dremel with grout removal tool will work.

Was thinking dremel, but wasn't sure how I'd get at the spot. It is about 12 inches in from the pipe opening and then at a 90 degree turn into the tee opening. Wondered about an extension attachment, but not sure it could be positioned or maneuvered down the pipe.