Determine size of pipe (for a new bathroom sink)?

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Old 09-12-08, 08:26 AM
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Determine size of pipe (for a new bathroom sink)?


I'm installing a new bathroom vanity/sink in one of the bathrooms in our home (just moved in, first home) and looking for some advice.

When I remove the old vanity/sink, I'm also going to be removing the old plumbing (p-trap, etc. as it looks like it's seen better days...). All I'll be left with is the drain pipe (about 1/2" sticking out of the wall) and the two water pipes/flex lines (hot & cold) to attach to the new sink.

Basically, I'm wondering how I determine the diameter of the old drain pipe (which, as I mentioned above, is sticking out about 1/2" above the wall)?

Oh, and the piping used that comes out of the sink (drain), the p-trap, etc. basically, all the pipe from the sink drain pipe to the last pipe BEFORE the drain pipe (in the wall) is that typically a "standard size" (my region is North America, Canada specifically) or will this vary? I only ask as I'll be hitting the plumbing store after work and if I don't have to make a second trip to buy all the pipe, all the better. 8)

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Old 09-12-08, 02:00 PM
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Standard bathroom drainage size is 1 1/4 inch.The pipe sticking out of the wall is usually 1 1/2 inch.If it is metal and threaded,there is an adapting nut that will reduce it to the 1 1/4.If you go to a real hardware store or plumbing supply they will know what you need as this is all plumbing 101 basic plumbing knowledge.

Take your old peices with you to show them what you need and arm yourself with all the description and info you can.

Pipe size is determined by the inside diameter of the pipe.If your pipe in the wall is plastic and has a threaded adapter glued on take the nut with you.If it's plain plastic get the inside diameter.
Old 09-12-08, 02:06 PM
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Thanks! I'll post the results!
Old 01-04-14, 07:47 AM
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How did it go? (Or have you been wandering around the plumbing store for five years? )
Old 01-04-14, 11:19 AM
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