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Every day when I have a shower, the drain starts out plugged. The water from my shower will slowly fill the tub. After about a minute or 2 the drain will unblock itself and the water will all drain out normally. The tub will stay unblocked for the rest of the shower, but will return for my next shower. This has happened for every shower that I've had for the past month or so.

Why is this happening? Is something wrong with the plumbing?

  • It sounds more like the VENT is plugged (or missing) than the drain itself. – jwh20 Jan 2 at 18:54
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    I can't see a vent holding back an entire tub of water (and why is it a temporary problem?). Strabbi, try to determine if the tub drains slowly at first or not at all. Shut the water off before it lets loose and see what's happening. Could be a helpful clue. – isherwood Jan 2 at 19:09
  • @jwh20 There's a lot of misinformation out there, but blocked vents do not cause slow drains. Before you quote the inverted soda bottle analogy, note that there is no such thing as a plumbing fixture with only one way in/out like a soda bottle - every plumbing fixture ever made is open to the air on top. Air does not need to "switch places" with water coming down the pipe - if the air doesn't have anywhere to go, the water doesn't, either. Vents are there to prevent P-trap siphoning, not to make the drain run faster. – Nuclear Wang Jan 2 at 19:58
  • The pressure on the drainage system depends only on the elevation of the water in the tub -- a cylinder of water right on top of the drain exerts the same pressure as the entire tub filled to the same depth. It could be interesting to make a water column around the drain and pour water into it manually. Absent the sounds of running and splashing water, one could listen to and observe the drainage. A piece of large-diameter pipe, a cylindrical food container with the ends cut off, etc could contain the water in a column so that a gallon or less of water is needed. – Greg Hill Jan 2 at 20:01
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    turn the shower off for 30 seconds, then turn back on ... does the symptom repeat? – jsotola Jan 3 at 3:28

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