Sulphuric Acid

Hi all,
I have a 32mm waste pipe which is vitually blocked with soft deposits (I cut it to move the sink). The pipe goes under the floor and I dont want to replace it if I dont have to. Can anyone recommend the best substance for clearing it once the new sink is connected? There wasn't a problem before with emptying the sink but I'm keen to avoid one in the future. I've used sulphuric acid on external drains and that worked well. Thanks

caustic soda is very good, but do read instructions first, if not it will BLOCK the pipe

I quite often go out to pubs and use sulphuric acid based drain cleaner
its very good I use one big shot to get it clear then the customer uses another litre over the course of a week to clean it.

It saves a lot of disruption.

Make sure the trap is clean first and stand back coz it takes no prisoners.

thanks guys