Drain fittings

Old 01-25-21, 06:09 PM
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Drain fittings

Installing new kitchen sink. I bought this P trap kit.Keeney 400PVCK PVC P-Trap Pipe Kit with Reducing Washer ... https://www.amazon.com/dp/B005J3WVNC/ref=cm_sw_r_sms_api_glc_fabc_qE3dGbJ4HHPKF?_encoding=UTF8&psc=1

The pipe coming from the wall is quite long since the old sink was catty corner and this one is now perpendicular. I know I have to cut the pipe shorter, but how short? Also the wall tube (marked letter A) can slide all the way into the existing piping. How far into the pipe should the wall tube go into the adapter (marked B) then into the existing pipe? Does it matter how deep the wall tube is inserted into the pipe coming out from the wall? Thanks.

Old 01-25-21, 07:03 PM
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At a minimum, it needs to go into B far enough that the compression ring seals and so that it does not slip out. And it does not really matter how far past B it extends, with the exception that you do not ever want to to be so long that it jams itself into a tee or elbow, since that could obstruct the flow.

A good rule of thumb would be to be sure that A will extend fully into B. It does not "need" to be longer.
Old 01-26-21, 05:34 AM
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Piece your drain together and hold it up next to the pipe coming from the wall to see how much you need to cut off. When in doubt leave it longer because you can always cut it shorter if needed.

I like to leave pipe A at lease a couple inches longer than the distance to fitting B. This leaves adjustment in case you cut something wrong. You can always make it shorter if needed.
Old 01-26-21, 05:44 AM
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Thank you. What's a good length from the finished cabinet to cut the pipe coming out of the wall? The countertop isn't in yet so I can easily cut it now from overhead (it gives me more leverage than when the counters are installed).
Old 01-26-21, 07:12 AM
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Wait for the counter top and sink is installed then measure and cut. It may be a bit harder but you'll be sure of exactly how short to cut it.
And like stated before, make it slightly longer than needed but not so long that it hits the elbow.
jay060 voted this post useful.
Old 01-26-21, 10:42 AM
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The counter is 24", and the sink drain is centered approximately half of that. I usually rough out my drain to about 8" from the back of the cabinet. I usually also offset it 3-4" off center or so to the left or right as it makes the trap easier to assemble and adjust, but isn't necessary.

As others have suggested, I don't install the slip adapter until the sink is in and the trap is almost in. It's a pain to cut once the sink is in, but certainly doable.

Don't forget about caulking or adding a eustachian on the pipe where it goes through the cabinet.

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