Most blocked drains are a straightforward clear. The ones worth paying attention to are the ones that come back.
There are two kinds of blocked drain. The first is a one-off — something went down that should not have, it caught, and clearing it is the end of the story.
The second keeps happening, because something in the pipe is catching debris every time: roots, scale, a sagging section holding water, or a hard layer of cooled grease. Clearing that one without looking at why just books you the same call again in a few months.
So on a repeat blockage or a main line we put a camera down afterwards. It costs a little more on the day and it is the difference between a fix and a subscription.
If the basin and the tub are both sluggish, the problem is not in either of them — it is in the branch or the main they share.
Run an upstairs sink and listen to the downstairs one. Gurgling means air is being displaced past a partial blockage further down.
A drain that blocks every few months is telling you something is still in there. That is a camera job, not another clear.
Blocked drains rarely travel alone. Here is what else we handle.
Cleared properly, with an honest answer about whether it will come back.