The drain never had the fall it needed
Waste moves because the pipe drops as it runs. Where the fall is too shallow, water gets away and solids do not. They settle, they build, and the pipe narrows until the day it closes.
This is the cause behind most washrooms that block on a schedule, and it usually dates to how the run was laid rather than to anything anyone did since. It is common in buildings where a washroom was added to a floor that was not planned for one. The fix is to relay that section with the right fall, which is a bigger job than a clearing, and the only one that ends the cycle.
Something is going down that should not
In a public or staff washroom, the drain receives whatever the building puts in it. Paper towels, sanitary waste, cleaning rags and food waste from a nearby kitchen all reach pipes that were sized for none of them.
The clue is where it blocks. A single cubicle blocking repeatedly points at what is being put into that cubicle. A whole block backing up at once points further down the line. Before paying for the same clearing again, it is worth putting bins in the cubicles and seeing whether the blockages stop.
Scale and grease have closed the pipe from the inside
Lahore water is hard, and hard water leaves deposits. Over years those deposits narrow a pipe until its real diameter is a fraction of what is printed on it. Add grease from a kitchen line and the narrowing accelerates.
A pipe in this condition blocks easily and blocks often, and the clearing that worked last year buys less time each time it is done.
The blockage is not in your section at all
In a multi-tenant building, a ground floor washroom backing up is often carrying what the floors above sent down. The blockage sits in the shared stack, and the tenant paying to clear their own branch is paying to fix nothing.
The tell is simultaneity. If several tenants report slow drains in the same week, the shared line is the place to look, and the building management rather than each tenant separately should be handling it.
What to check before calling anyone
Note whether it is one fixture or the whole block, because that single fact narrows the cause more than anything else. Check whether the blockage follows a pattern, such as always on a Monday, which points at weekend usage or at something being poured down before the building closes. Look for damp on the wall or the ceiling below, since water appearing there means the problem is already past the drain.
Do not keep pouring drain chemicals into a line that blocks repeatedly. They do little against scale, they damage older pipes, and they make the eventual repair a harder and less pleasant job for whoever opens it.
Why the repair often needs more than a plumber
Getting to a buried or boxed-in run means opening a wall, a floor or a ceiling. The pipe work is the short part; making the space usable again is masonry, plaster and paint, and sometimes a door or a panel put back.
We handle the civil and carpentry side as well, so the washroom is closed and finished on one order rather than left open while a second contractor is arranged. For a building where that washroom has to reopen tomorrow, this is usually the part that decides how long it stays out of service.
This is work we do. Plumber & Plumbing Services in Lahore covers the scope, and a site visit comes before any quote.