My bathroom sink was leaking from the pipes underneath it so I replaced all the pipes going into the wall and also replaced the trap. The pipes don't leak anymore but for some reason the sink won't drain, it takes about an hour for a little bit of water to go down, how can I fix this?

What type of lavatory do you have ? A regular bowl or a vessel sink, ( a lavatory with no overflow.)? If a regular bowl then run a snake up into the wall and clear the line. If you have a vessel sink click on back. Tom

It is a regular bowl. The thing is before I replaced the pipes it drained perfectly, it's only been since I replaced the pipes and trap that it has been draining slowly. Would cleaning out the pipe in the wall with a snake fix it?

Would cleaning out the pipe in the wall with a snake fix it?

That would be the advice that I would give. You must have lloosened some crud built up in the pipe walls when you changed out the pipes. Remove the "J" bend from the trap and send a snake up into the wall for about 6 feet. Good luck, Tom