Schedule 40 versus 80 pvc for dive light rig

[heehee62]

It doesn't matter if I get schedule 40 versus schedule 80 pvc for my DIY lighting rig does it?

I'm thinking about getting furniture grade schedule 40 pvc as it comes in different colors(no threads though). Thanks.

 

[Dsix36]

It depends on how deep you plan to take it. I would venture a guess that schedule 40 will be fine for your application.

 

[heehee62]

It depends on how deep you plan to take it. I would venture a guess that schedule 40 will be fine for your application.

135 ft max

 

[Dsix36]

135 ft max

Schedule 40 will be plenty good enough for you. It will handle much deeper if needed.

 

[Akimbo]

I suggest testing it yourself on the end of a rope. Schedule 40 PVC's tolerance to withstand external pressure goes down as the diameter increases. There is no rating for external pressure like there is for internal pressure. You do want a pretty good safety margin with PVC. It doesn't have great impact resistance and an implosion can be very dangerous.

 

[Tom Winters]

Ah geez... he's using what - a foot of pipe? Get the schedule 80. It's gray so you won't have to color it. 2.5" diameter 5' long with shipping might run ya $20.
If you do use schedule 40, go for the furniture grade and get some dye stain from eBay to color it. They use this stuff in the petroleum industry to color code piping and it won't come off.
I sure don't what depth you'd have to dive a schedule 40 canister to implode it, but I'll bet by the time you did get to the depth, you'd be long past the point of caring.
Have fun with that.

 

[Dsix36]

I know for a fact that a piece of 3" schedule 40, 12" long, with both ends capped; will not implode at 484'. I think that might be as deep as I would want to take it though.

Akimbo is absolutely correct in the rating being for internal pressure and that the bigger the pipe is the less external pressure it can withstand. I have always just used the internal pressure rating to figure the depth rating of my projects, but 6" pvc is the largest that I have ever used for scuba.

 

[Akimbo]

With the exception of the theoretical “perfect” sphere, external pressure ratings are less than internal pressure for a given vessel — usually by several times. You can improve external pressure ratings on a cylinder by adding ribs, which is what is done on submarines.

Calculating internal pressure ratings are pretty straight forward and are dominated by geometry and material tensile rating. Calculating external ratings is far more complex and failures usually begin as deformation and rapidly cascade from there.

 

[AngloFish]

I can't say for sure the stuff I'm using is schedule 40 or not, but it's standard black 2" plumbing pipe. ABS cement to seal the end caps and so far I've been using them for about a year to make my rig neutral.
Has worked like a charm so far, typical depths are 90-130. Total cost for the pipe was $8.

 

[Akimbo]

Black plumbing pipe is ABS, white plumbing pipe is PVC, gray plastic electrical conduit is PVC. Nearly everything you can get at a home improvement store is Schedule 40.