A story about backpressure

The other day, I noticed our bathroom sink was slow to drain: although the stopper was fully open, standing water was just trickling down. I peek inside the drain and saw some hair sticking out - aha!

It's easy enough to dissemble the stopper (with the help of this instructional guide), and quickly I am rewarded with a surprisingly large wad of soapy hair.

Triumphant, I reassemble the stopper and run the tap full-blast. Water flies down the drain... until suddenly, it doesn't. I shut off the tap, and the water level sits high and unmoving. Oops.

It turns out the hair-filled stopper was a distraction from the true problem: a bigger bottleneck in flow rate farther down in the system. Seeing the sink slowly fill up with water was actually useful backpressure: a signal that told me to stop pouring water into a pipe that couldn't handle so much, so fast.

But anyways, I would prefer an unclogged sink, so I find my wrench and take apart the P-trap. Nothing obviously blocked there. My landlord, or perhaps the previous tenant, helpfully left a drain snake in the cabinet under the sink, so I dig into the next section of pipe. This yields some disgusting chunks of biofilm-y semi-solids, and I'm confident enough to try again.

Once again, I run the tap full-blast. This time, water flies down the drain for long enough that I felt bad about wasting it. What a relief.

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Thanks to Yee Aun for moral support. Thanks to the landlord and/or previous tenant for leaving a drain snake - unlike my previous landlord John, who insisted on pouring not one, but two jugs of Drano into our kitchen sink (after I already bought a hand-crank snake and failed to clear it!), and made us wait multiple days with no usable sink before calling a real plumber with a longer, powered snake.