Key takeaways
Kitchen drains clog with grease and food; bathroom drains clog with hair and soap scum, so the fix differs by room.
For a kitchen sink, start with hot water and dish soap or a plunger; for a bathroom drain, pull the hair out with a drain snake.
Treat caustic soda as a last resort: it is corrosive, can damage older or plastic pipes, and should never be mixed with other products.
If several drains back up at once, or one keeps blocking soon after you clear it, the blockage is in the shared waste pipe and needs a plumber.
Where is it blocking? The quick check
First, notice how many drains are affected, because that tells you where the blockage sits. If only one sink or floor drain is slow, the clog is usually local, in that drain or the U-bend just below it, which is the kind you can often clear yourself. If several drains run slow or gurgle at the same time, the blockage is further along the shared waste pipe that serves the whole house, and that points to a plumber. Call it the Two-Drain Test: one affected drain is worth trying yourself, two or more at once means the main line.
A blocked kitchen sink: grease and food
Kitchen drains block with cooking grease and food that cool and harden inside the pipe. Start with hot water and a squeeze of dish soap, left a few minutes, then flushed through. If it is still slow, half a cup of baking soda followed by white vinegar, left fifteen minutes and rinsed, breaks down softer build-up. A plunger is the next step: fill the sink to cover the cup, seal the plug hole, and pump firmly. Keep the water hot, not boiling, since boiling water can soften plastic pipe.
A blocked bathroom drain: hair and soap
In the bathroom, the usual cause is hair, which collects in the drain and mixes with soap scum into a soft, stubborn clog. A plunger can help, but the reliable fix is to pull the hair out. A drain snake (the flexible wire sold as งูเหล็ก), or a wire coat hanger straightened out with a small hook bent into the end, pushes in and twists to drag the clump back up. On a basin, the stopper usually lifts or unscrews so you can clear the hair wrapped around it. Pulling it out by hand works better than pouring anything in, because liquid just runs past a solid clog.
What should you pour down a blocked drain?
Different blockages respond to different things. Here is what each option is good for, and where it falls short:
Method | Best for | The catch |
Hot water and dish soap | Kitchen grease, light build-up | Safe, but will not shift a solid clog |
Baking soda and vinegar | Smell and soft grease | Mild; a maintenance flush, not a fix |
Plunger | Most sink and floor-drain clogs | Needs a firm seal; messy with standing water |
Drain snake | Hair and deeper clogs | Best on solids; takes a little effort |
Caustic soda | Stubborn grease, last resort | Corrosive to skin, eyes, and older or plastic pipes |
Caustic soda is what many reach for first, and it does cut grease, but it is corrosive and hard on older or plastic pipes with repeated use. Use it as a last resort, with gloves and eye protection, and never with another product.
When it is a plumber’s job, not a DIY one
A few signs tell you to stop and call a professional. If several drains back up together, if a drain clogs again soon after you clear it, or if you notice a stale smell and gurgling across more than one fixture, the blockage is in the main waste pipe, beyond the reach of a plunger or a shop-bought drain cleaner. A plumber can locate it and clear it with a powered drain auger.
As a rough guide, a simple drain clearance in Bangkok tends to start around ฿700, and more involved jobs can run to about ฿2,500, with any parts charged on top. On gigit you set the price, not the platform: choose your own budget for the task, or leave it open to offers. Identity-verified plumbers near you then send their offers, and you only pay once the job is done. If the problem turns out to be the toilet rather than a drain, see how to unclog a blocked toilet.
When a drain is beyond a home fix, post a plumbing task on gigit: set your own budget or leave it open to offers, then choose from the offers local gigit heroes send.