3" ABS - Simplest question ever.

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Unique Handle

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In a nutshell, I can't seem to insert 3" ABS pipe "all the way" into a straight-through coupling.

The coupling fits perfectly on the existing 1960s-era 3" ABS. The 3" pipes I just bought from Home Depot (and another length from Rona), however, fit in about 3/4" of the way (i.e. about halfway) before it binds ... tight. I had to use a chain-wrench to get it off.

I twist, I push, I'm a big guy. I've done quite a bit of DIY plumbing over the years and never came across a problem like this. Is there such a thing as a lubricant for test fitting?

Any advice would be appreciated, especially from my wife who has little patience for toilets sitting in the hall.
 

Geniescience

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it won't dry fit. That is the simple answer. Only after you get the right liquids on it will the two pieces fit together, and then it's too late to test it out, since you have to hold them in place and let them glue themselves together.

i don't know why so many people talk about dry fitting.

david
 

Kordts

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Plastic pipe and fittings are "interference fit" They don't bottom out without the solvent cement(glue.)
 

Gary Swart

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The so-called "glues" that joins ABS and PVC are not really glues at all. They are chemical solvents that actually melt the outer surfaces of the pipe and fitting. This allows the pieces to slip together easily as long as the pieces are joined fairly quickly. The melted surfaces then join together. The process closely resembles welding except it is done with chemical reactions rather that high heat. Note: ABS and PVC do not use the same solvents, but the processes are the same. Fortunately, you do not have to cut ABS or PVC to absolutely perfect lengths. There is usually some slack to allow a slight length adjustment so perfection is not required.
 

Verdeboy

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Dry Fitting

I think the problem lies with the instructions on the PVC/ABS Cement can. It says to dry fit first. Then it goes on to say when dry fitting, the pipe will only go 1/4 to 3/4 of the way into the fitting. But people seem to not read that part.
 

Gary Swart

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I lay no claim to being an expert, but when I am working with ABS or PVC, I use a felt marking pen to mark the pipe for cutting. I either lay a piece of pipe between the fittings or measure from the middle of each fitting then mark the pipe. Marking pen marks are easier to see than pencil, especially on black ABS. I do the same with copper pipe. You rarely have to be so finite that even 1/8" more or less will make any difference.
 
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