you should go to ace hardware, and buy drain opener.

Ace hardware sells many of them. The best one is "i forgot the name"... but i recalled from all the collection, it has plastic bag sealed wrapped the sealed bottle... all drain opener are liqued, stored in sealed bottle. this one lagi best, it has plastic sealed wrapped outside sealed bottle... the bottle is white, the brand written in red / black printing. and it has word "professional grade"... sure will not miss lah..

these things sure real posion so make sure you know what you are doing, protect ur hand, don't let it sprink to ur skin and... it smells acid badly so make sure ventilation is there

PVC melted because you leave it longer than 1 hour without any water. actually i think 15 minutes already overloaded...

have you notice when you pour the acid there is a smoke and smell ? that's when the acid eat up everything inside the pvc... then after the smoke and smell gone, wait for 15 minutes - 1 hour (depends on how big the pvc is) and then you flush it with water.... flush it with plenty of water. i mean reallllllllllllllllllllllyyyyyyyyyyyyyyy plenty of water. This is to disolve acidic texture inside pvc...

The name is Rooto. You can google image the keyword below:
rooto professional drain opener

Hey... i recalled alkaline based clog remover.... try mix with acid based clog remover if still stubborn... sure feel like "nasi goreng meletup"