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-   -   The Twist (http://www.houserepairtalk.com/f33/twist-10199/)

john4153 10-23-2010 05:01 AM

The Twist
 
I am solvent welding ABS and noted that manufacturer installation instructions differ from each other.

One manufacturer instructs one to insert the properly prepared pipe into the hub and then twist 1/4 turn. Another manufacturer instructs one to insert the pipe into the hub with a twisting motion. It specifically cautions against twisting once the pipe is fully inserted.

Which is correct? Since the fittings and pipe all meet the same standards, it does not seem that both could be correct.

Now for a second, but related question. There are certainly going to be times when a full 1/4 twist, or even any twist for that matter is not possible. What can one do to compensate for that factor? More solvent-weld adhesive? Two coats of adhesive? In other words, just how critical is the twist?

I have done small projects before with PVC, but this is my first attempt with ABS, so I read the instructions.

John

Redwood 10-23-2010 08:34 AM

Hi John

The cementing of plastic pipe is actually a solvent welding process.
The cement softens the plastic for a brief period and you join the pipe together, then it hardens again.

The cement is applied to both sides and makes a thin soft layer on each side which is then mixed together with the twisting motion and held in place until it sets again.

Excessive amounts of cement may soften the plastic to deeply and weaken the joint. Excessive twisting may move the joint while it is in the process of hardening causing voids in the solvent welded joint which can fail.


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