Fill a kettle and boil it. Pour the entire kettle down the slow drain in one go. Wait 10 minutes. If the water drains faster, the clog was mineral buildup or hardened soap. Repeat once more if needed.
Most slow bathroom sinks have a popup stopper that unscrews. Hair usually wraps around the stem. Pull out what you can grab. Rinse the stopper and put it back. This fixes drains clogged right at the surface about half the time.
You can buy a cheap plastic hair snake at any hardware store for a few dollars. Feed it down the drain, twist it, and pull it back up. It will catch hair and debris. Flush the drain with hot water after.
If boiling water and a snake don't work, the clog is deeper in the line or the pipe is narrowed by mineral buildup. A plumber can use a powered snake and camera to see what's actually blocking the flow.
Slow drains in Seaside homes are almost always hair, soap scum, and mineral deposits bunching up in the trap under your sink or in the main drain line. Every time you shower or brush your teeth, a tiny bit of hair and skin oil goes down the drain. It seems insignificant, but hair tangles on itself and on any rough spot in the pipe. Soap residue hardens and sticks to the pipe walls. In older homes and buildings here, the pipes are often steel or galvanized iron, and our water's minerals coat the inside of the pipe slowly, narrowing the hole the water has to flow through.
The difference between a slow drain and a completely blocked one is time. A slow drain today is a warning. Water backs up a little, maybe drains overnight. A clogged drain is an emergency: water won't drain at all, or it backs up into the shower or tub. When you hear gurgling from the drain when you flush the toilet, that's a sign the blockage is in the main line that serves the whole house. That one needs a plumber with a camera and motorized equipment.
Most people wait too long to deal with slow drains. They use drain cleaners that eat away at the pipes, and when those don't work, the blockage is now compacted deeper and harder to reach. A plumber with a drain camera can see exactly where the clog sits, whether it's hair, mineral buildup, or something else, and clear it in one visit instead of you trying three home remedies.
Describe what you're seeing to a real Seaside plumber: call (831) 555-0140 or send the form. Free, no obligation.