Need help with bulkhead size.

[Bao]

Hello all,
I just picked up a 1" bulkhead from skipton and was informed that I need to drill a hole with the diameter of 1-3/4". isn't 1-3/4" way way too big for this small bulkhead? I measure the outside wall of the bulkhead (the smaller end) and it is only 1-3/8". The bigger end of the bulkhead is only 2". I read everywhere, it is recommended that I need to drill a hole with diameter of 1-3/4" for a 1" bulkhead. But when I actually measure the bulkhead, it just doesn't make sense to me.
thanks,
Bao

 

[maxfischer]

1-7/8"

 

[JohnK]

Hello all,
I just picked up a 1" bulkhead from skipton and was informed that I need to drill a hole with the diameter of 1-3/4". isn't 1-3/4" way way too big for this small bulkhead? I measure the outside wall of the bulkhead (the smaller end) and it is only 1-3/8". The bigger end of the bulkhead is only 2". I read everywhere, it is recommended that I need to drill a hole with diameter of 1-3/4" for a 1" bulkhead. But when I actually measure the bulkhead, it just doesn't make sense to me.
thanks,
Bao

Sounds like you've got a 3/4" bulkhead.

 

[stingythingy45]

^^^

Yup,better measure the inside diameter.

 

[Bao]

No it is a 1" bulkhead. The diameter of the inside of it is 1".

 

[JohnK]

There's the confusion. Whoever decided how PVC is sized was not concerned with reason Regular schedule 40 PVC is sized by the inside diameter, ie 1" PVC is about 1.02 inside diameter. BUT it gets confusing when you consider that there is also heavy duty schedule 80 PVC which has a smaller ID, but the same OD. Hence 1" PVC is always the same outside diameter (which is not 1"), but the inside diameter will be smaller with schedule 80, so with schedule 80 PVC neither the ID or the OD is anywhere near 1"

FWIW,
1" schedule 40 PVC (this is the normal PVC you get at HD/Lowes) is aproximately 1.31 outside diameter. 3/4" PVC is actually 1.05" outside diameter.

You've got a 3/4" bulkhead. The inside of a 1" bulkhead will be about 1.32" Confusing and annoying, huh

 

[JohnK]

Oh yea, there's one more layer of insanity...

Bulkheads are either regular or "heavy duty schedule 80". With bulkheads, the inside diameter will stay the same size (1.35ish " ) but the schedule 80 ones need a larger hole drilled in the tank.

IIRC regular would be a 1 3/4" hole, and sch 80 would be a 1 7/8" hole. (I'm not %100 positive on the size for the sch 80 bulkheads, I know standard bulkheads do fit in a 1 3/4" hole).

Last I checked skiptons only carries the regular ones. Regular ones come in black, blue and clear. The sch 80 ones are usually dark grey colored.