Connecting two slightly different-sized CPVC pipes

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Old 09-23-18, 04:39 PM
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Connecting two slightly different-sized CPVC pipes

Hey everybody. I just needed some general guidance to see whether my idea would work.

Today, I heard a rush of water under my bathroom sink. I checked and, where the U-bend connects to the main pipe, the connection is not sealed. It was presumably sealed before this time since there's been no leaking water. Here's the dillemma. The piping on the U-bend (from circa 2013) is slightly larger (1cm or so, just enough so that they don't fit snugly) than the main drain pipe (circa early 1990s). Both are CPVC. The U-bend fits slightly over the main pipe with the main pipe going inside of the U-bend just slightly, similar to how a CPVC connector would but not quite as deep.

Theoretically, I would assume the best option would be to replumb the entire area. But, given the main drain size being slightly different, it's going to need to be played with no matter what unless I replumb the entire area under the house, so I would prefer to simply find the best way to seal the pipes together since they are above the floor/not inside of a wall (the vanity cabinet houses/hides the pipes - easy access and out of sight).

So: how would you recommend sealing the two pipes together since a traditional CPVC connector would not really work in this scenario. Here's my idea: use bathroom caulk or plumber's putty (please tell me which is best) to create a primary seal between the two pipes. Apply a coating of Oatey outside of the caulk/putty after it's set. Apply a layer of gauze around the connection and apply another layer or two of Oatey to set the gauze.

Is this practical in your opinions?

Thanks!
 
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Old 09-23-18, 04:54 PM
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I am confused. You say CPVC pipes but your description sounds more like the drain line. Where are you located? That might help understanding your terminology.
 
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Old 09-23-18, 05:17 PM
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Tennessee- The drain line from the sink that goes into the main waste drain/sewer is the same material as the rest of the piping under the sink, CPVC (or at least what we refer to as CPVC). The loose connection is right under the sink where the U-bend (CPVC) connects to the straight, up-and-down drain line pipe (also CPVC) that connects at some point under the house to the main sewer/waste line. The entire house is piped with CPVC except for the gas stack and a few main pipes in the front yard near the city connection that are ABS.
 
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Old 09-23-18, 05:32 PM
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Sounds like you could use a shielded Fernco rubber coupler.
 
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Old 09-23-18, 05:59 PM
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It's very odd to see CPVC as a drain line. I didn't even know they made larger than 1" CPVC.

I like XSleeper's suggestion of a rubber coupling, they can adjust to different sized pipes pretty easily.

Though maybe a picture might help us give you a better solution.
 
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Old 09-23-18, 06:12 PM
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Thank you - sounds like a good idea since the pipes are just barely different sizes and need a sem-flexible connector. What kind of glue would you recommend for a rubber-to-CPVC connection? I've always used the red all-purpose Oatey, but some people don't seem too fond of it just from things I've read lately as I learn more about DIYing.

EDIT: Didn't see Zorfdt's reply

I'm just basing it on what's immediately visible right under the sink. From what I remember years back when I went under the house, the drain pipe widens (still CPVC though) under the floor where the sink is. This is just the initial connection right under the sink. I've seen CPVC up to 6" around here fairly often, at least in homes I've lived in/family members' homes. Around here, metal piping is very rare in anything built after 1950.
 
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Old 09-23-18, 08:04 PM
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You don't use glue with rubber ferncos. I believe that around here cpvc drain pipe was pretty common in the 70s, but pvc schedule 40 took over in the 80s, and yes, the two sizes don't match up.
 
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Old 09-24-18, 04:53 AM
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Are you certain you don't have white plastic trap and lines. The pipes are different sizes and one pipe slips into another and is sealed with a plastic slip washer and nut.
 
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