Levelling Compound in Drain !

[Spinny]

So our flooring contractor has managed to pour floor levelling compound down one of our drains !

We have a rain water drain that is completely blocked at the u-bend.

Other parts of the drain had deposits.

 

Is there any way we might be able to unblock the rain water drain ? Some kind of solvent or acid ?

 

Plumber cleared some from the vertical part of the drain using a very long drill bit, but clearly won't go around a bend.

 

Drain pipe is clay. Levelling compound is Bostik C530 which has fibre reinforcement.

Edited 8 hours ago by Spinny