Why are winterizing plugs tapered?

Texas Splash

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Jun 22, 2014
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I wonder if it's because there are many pools, especially older ones, that were plumbed with odd sizes, and the tapered fittings help to accommodate insertion? Just a wild guess unless there's an engineering reason for the shape.

 
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ajw22

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Jul 21, 2013
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Northern NJ
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You are rarely plugging directly into a schedule 40 pipe that has a consistent I.D. You are plugging return fittings glued onto schedule 40 and skimmer holes whose inside diameter can vary. A tapered plug can seal against any manufacturing variances.
 
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Quickstep192

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Jun 30, 2022
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Annapolis MD
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These plugs are generally used to pressure test (at 60 PSI) the same type of PVC pipes that are used in pools, so I’d imagine they’re equally capable of deforming to accommodate variances in ID. By the way, my returns are just the pipe with no fittings or threads. My skimmers are threaded, but I use Gizzmos in those.
 
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