ABS gluing questions

[DavidTu]

I had to replace a fitting in a tight space and found that to insert the new fitting there was not a lot of clearance to get my glue swab between the (existing pipe) and the replacement fitting hub... I did my best to spread around the cement and think I got it pretty well covered. I was not able to do a full 1/4 rotation after bottoming the pipe. In another instance, it seemed like I was able to rotate a joint slightly after having let it set-up for 15 secs or more.

So... my questions are:

1. how sensitive is the ABS cement joint regarding both pipe and hub being completely covered w/ cement?
2. if a joint still can move even slightly (ie. has play in it) after 15 secs or so does that imply too much cement was used and does the joint need to be redone b/c the movement damaged the set-up?
3. if a joint is bad is that something that will show itself during the water test and/or pressure test or do these problems tend to sit dormant for long periods before starting to leak?

 

[hj]

1. If both pipe and fitting are not completely covered, (and at least one must/should be), and if there are any gaps, they had better nto be at the same place on both the pipe and fitting.
2. It depends on which way it can move, and the size of pipe.
3. If it does not show up during a pressure test, it is unlikely to EVER have any greater pressure, and thus should not leak or fail.

 

[Sponsor]

 

[DavidTu]

Thanks HJ...

Re:
#1 So it sounds like applying cement to both parts is designed to assure absolute full coverage? If one were to only coat one part w/ cement... but was done thoroughly and liberally--hypothetically speaking--would that usually suffice for a good joint? In real-life situations are there ever occasions to only coat one part?

#2 The joint was still able to rotate a bit. I was suspecting there was too much cement applied... but concerned that the movement would disengage the joint... sort of like cause a cold soldering joint. In practice, is it likely that movement after 15-30 secs just means there is extra work-time and the joint should seal well or more likely that it will be a "cold joint"?

#3 Whew! So it sounds like pressure test (rather than just a standing water test) is necessary to really test the joints?

 

[Gary Swart]

David, the thing you need to understand about ABS and PVC "glue" is that these are not glue as we usually think of glue. These are solvents that melt the top surfaces of both the pipe and fitting so that when the pieces are slipped together, the two surfaces mix together and form a welded joint. Although ABS and PVC are different materials and their solvents are different as well, the process is the same. Proper procedure is, as you know, to coat both surfaces with "glue" and rotate upon assemble. In reality this may well be a bit of overkill. The idea is to have full coverage of the interior of the joint. Coating both surfaces alone will do that. Rotating the joint will further insure that this is done. Is it all really necessary? I doubt it. Good practice? Yes, vital to a good joint? Probably not. Too much "glue"? Wasteful and messy, but not harmful. Once a joint is slid together, it should be rotated immediately then left alone. Don't continue to try to rotate it or otherwise move it, that can break the "weld" before it has fully set. Trust HJ's advice, he's about as knowledgeable as anyone on this forum.

 

[DavidTu]

Once a joint is slid together, it should be rotated immediately then left alone. Don't continue to try to rotate it or otherwise move it, that can break the "weld" before it has fully set.

Well... hate to admit it but I guess I may have rotated it after having left it alone... should I assume it's a bad joint or assume it will show itself in the leak test? Btw... hope to hear regarding the effectiveness of a water leak test vs. the pressure test (ie. is the latter the "only way to go"?)
Thanks for your help Gary & HJ.

 

[Shacko]

Normally drainage is tested with a stand pipe 10ft. above the highest joint and it's all filled with water, let it sit for a time, check for leaks and drain it out.

Pressure tests (air) are usually limited to 5lb. psi. you have to cap off all the lines and fill it with air, these are harder to do because an air leak is harder to find. You don't use a lot of pressure in plastic type pipe because it won't take a lot of air before it splits.

 

[hj]

A standing water test, if done correctly, IS a pressure test.