Securing double wall pipe with sheet metal screws.

[Ditchmonkey]

I had some help getting my Fireview installed and now I'm thinking the guy didn't do a great job:

1. He didn't pre-drill any of the holes. I discovered later that 2 of the 3 screws in the DSP adapter did not completely pierce the adapter, and when we were installing the connector the adapter moved a little and the 2 screws pulled out.

2. He only used screws at the telescoping joint, not at either end of the telescoping pipe. This seems to not comply with any of the instructions I have seen.

So I am assuming I need to add some screws at the connector joints. Do I use 1/2 inch sheet metal screws at all joints? Do I ever need to worry about piercing too deeply into the pipe I'm screwing into? Pre-drill with 3/32 bit? At the top of the connector where it attaches to the adapter at the ceiling support, do I put the screws right through the tapered section?

 

[chemical_man]

1. Maybe they were self-tapping screws? Doesn't sound too secure. Make it as safe as you can/want it to be. Hard to say "go through" without seeing what you're referring to, that being said screws should not come out! Google search shows a piece with a crimped edge, I would have screws through the crimp, the adapter should be solid on the piece it is on.

2. Yeah, that's not enough. I have 3 at every pipe connection and 1 at my telescopic joint (so, my telescopic section has 7 screws). Duravent supplied the screws with the equipment, so I used them. They are 1/2 inch screws, I drilled pilot holes. As long as 3/32 is smaller than the outside diameter of your screws, should be OK. Start small and you can always go bigger if you need to (generally can't make a large hole smaller!).

 

[Highbeam]

I've never predrilled. The proper screws are designed to drill their own holes.

Also, depending on the install, it is not wrong to omit screws at the ends of the telescoping piece. My example was two inspected installations where I specifically asked about this. A single telescoping section is the only piece of pipe and it is locked extended by the screws on the slip. The top can't be screwed because there in nothing to screw to on the older duravent ceiling box and the bottom shoves into the stove and only the inner wall of the double wall pipe is against the stove collar. You can't screw into the stove collar without modifying the outer wall or crushing it.

 

[Ditchmonkey]

The screws were self-tapping. I'm wondering if the thin walled DSP adapter isn't a good spot to use self-tapping screws as it is prone to bending before the screw pierces it.

The Selkirk connector pipe instructions specify 3 screws at every joint. I'm just unclear as to where exactly to put the screws (as Highbeam illustrates in his post).