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Author:
nicholas123 (FL)
I am installing a new horizontal drain pipe from my bathroom sink to the vertical stack. I was concerned about the smooth bumps inside the new 1-1/2" sch. 40 pvc pipe I bought...see below.
[i93.photobucket.com]
But then I became less concerned when I looked at the groove created by the coupling...see below. This was from an old job.
[i93.photobucket.com]
Thought I should use a no-stop coupling to minimize the groove even though it would be less strong...no interference fit. But, as you read on, the groove may not be a problem.
So, I looked at my old drain pipe. see below. Picture looking into trap adapter...
[i93.photobucket.com]
I cut this old drain pipe in half. The bottom of the pipe, where the water flows, and is likely to clog, is on the right. Original installer didn't cut pipe square so large gap between adapter and pipe end. May not be a problem because tubular drain pipe slips in and probably over this gap. See below.
[i93.photobucket.com]
And a closer look at bottom half...
[i93.photobucket.com]
I was really concerned about adding the new coupling in the first photo in my drain line. I thought the groove would cause clogging. But if you look at the old pipe that came out, it had big grooves too and I can't remember it ever clogging in the past 30 years. Makes the bumps inside the new pipe look insignificant. Anybody know why these grooves don't cause clogging. Or, maybe they do and I've been lucky in the past 30 years. P.S. This old drain line was not even sloped right...it was sloped uphill to the stack.
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Author:
North Carolina Plumber (NC)
The grooves stay full of water in the bottom and the solids float across them ?
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Author:
bernabeu (SC)
the grooves 'should' not be there at all
the pipe ends 'theoretically' would be chamfered to 45 degrees and fully inserted leaving a smooth integral bore
however
nothing, including actual plumbing installations, is perfect
merely
as in your case
'good enough'
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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638
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Author:
nicholas123 (FL)
I learn something everyday...
I agree a 'smooth integral bore" would be the ultimate goal, but probably not realistic if you look closely at each connection point.
In order to close the gap, that is, minimize the groove...
Between the elbow and pipe, a huge chamfer would be needed.
Between the adapter and pipe, no chamfer is needed.
Between the coupling and pipes, a huge chamfer would be needed, not to conform to the fitting stop, but to bridge over the stop.
If you study these pictures closely, you will see what I am saying. The 'stop' in each type of fitting is different.
But even if you got the chamfer just right, so there is no groove, if the inside diameters are different between the fitting and pipe, you will still have a bump.
Bottom line, it is unreasonable to try to eliminate the grooves and bumps inside the drain lines. Just do your best. Try not to leave any jagged edges that can catch hair, etc.
I agree, water probably carries light crap over the groove. Heavy stuff, like sand, probably fills the gap over time.
I hope my anal retentiveness has benefited somebody. At least I can sleep better now knowing the truth.
P.S. I use to work at a paper mill, I vaguely remember having to cotton swab the inside of welded pipe to make sure there weren't any places for paper fibers to catch.
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Author:
bernabeu (SC)
EXACTLY the same principle
==============================================
"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638
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Author:
packy (MA)
the grooves you showed will do no harm..
look inside of cast iron pipe. it is no where near smooth.
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