HELP! Blocked sink - acid has made it worse!!!

[scampadoodle]

Our bathroom sink keeps getting blocked & up until now we've managed to clear it eventually - once we had to remove loads of gunk from the down pipe outside. However this time, despite lots of plunging & pouring sulphuric acid-unblockers down, it refuses to unblock. A plumber looked at it yesterday, checked the outside pipe (which was clear), & said there must be a blockage under the floor & to keep using the acid. I poured some more down this afternoon & now the sink is completely blocked (it always drained away before, eventually). HEEELLLPPP!!!

You can buy a sort of pump/plunger to unblock sings. It looks like a giant syringe with a rubber cup on the end and shoots a jet of water down the plug hole. It works a treat - I think it cost about £10 in Wickes

oh gawd, we had the same problem with our kitchen sink. Unfortunately ended up getting dyno-rod in to sort it out and took them 2 days to unblock it! they told me the stuff you can buy (Mr Muscle and all that) is all pretty useless. I guess they would say that, but seems to be pretty ineffective to me, so perhaps try fortyplus's suggestion first.

What product were you using scamp?

There's a really strong one that is only available in plumbers merchants called 'One-Shot' that is really good and eats through just about anything that could end up down the drain. It is about £5.00 a pot and extremely caustic so wear rubber gloves and eye protection if you use it.

yes, we've been using One shot & equivalent really strong stuff. The latest is something the plumber gave me which looks & smells lethal. We've now managed to unblock it, by using the acid and the plunger, but it blocks up again at the slightest thing so I'm just going to use the acid every week.
Thanks for all your advice!