Securing middle section of DVL telescoping piece

[sheneron]

I am finishing up the install of my DVL double wall pipe and the last piece is a telescoping piece and I am wondering how to screw the middle section as there are (obviously) no pre-drilled holes since the height is variable. The provided screws do not appear to be self-tapping, so do I buy 1/2" self-tapping screws and connect the pieces like that?

Also, I have another section of pipe where the pre-drilled holes do not line up due to the rotation of pipe with how I need my 45 angle positioned. Is there any issue to using my own self-tapping screws to attach that section of pipe as well and just not using the pre-drilled holes.

 

[begreen]

If it is secured a top, at each joint, and at the flue collar, then it doesn't need to be secured in there.

 

[sheneron]

If it is secured a top, at each joint, and at the flue collar, then it doesn't need to be secured in there.

Ok. Would there be any issue if I were to put a half inch or 3/8s inch self tapping screw in there? I need to do similar at another joint where the predrilled holes do not line up

 

[begreen]

No harm, as long as it penetrates both sections. A clear hole on the outer sleeve and a pilot hole on the inner will help.

 

[kennyp2339]

I wouldn’t screw the center, you will make it harder to remove the pipe for cleaning and maintenance, after removing the screw the metal has a dimple and it will rub on the other section