[Wet Thumb Forum]-tubing size

[chbak014]

how do i know what size tube i have? is the size the diameter of the tube or is it the circumfrence?
-charley

http://www.geocities.com/charleybak/aquarium.index.html

http://www.pbase.com/chbak014

[chbak014]

how do i know what size tube i have? is the size the diameter of the tube or is it the circumfrence?
-charley

http://www.geocities.com/charleybak/aquarium.index.html

http://www.pbase.com/chbak014

[Doomer]

Tubing is usually measured by inside and outside diameter. Inside diameter being the most critical. Most tubing I've seen has the size printed on it.

[gsmollin]

Unfortunately, if they don't say, then you don't know for sure. Pipe is alwyas an ID measurment. So, 1/2 inch copper pipe is an ID measurment. Tubing is OD measurement, so 1/4 inch copper tubing has an OD of 1/4 inch. The flexible aquarium hoses can fall into either camp, so beware. In most cases, it is very wise to ask, if, for instance, all you hear is "1/8" for the size.

[Rex Grigg]

Hmm... I always thought that tubing was a ID and pipe was OD. If you buy 4" PVC pipe it's 4" OD, because you can get both Schedule 40 and Schedule 80 in 4" and they have the same OD but the S80 has a wall thickness almost twice that of the S40. I could be wrong though. Would not be the first time.

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[deltaboy]

What is the specific question? Are you replacing a specific tube from a product? For example are u trying to replace your fluval 404 tubes but are not sure the size? Please be include this info...it might ring some bells.

[gsmollin]

Well, you bring up a good point, and it serves to reinforce my recommendation to ask the questions. For instance, here is a specification for schedule 40 and 80 PVC pipe:
http://www.harvel.com/PVCpipe4080spec.html
If you study it, you will see that 40 and 80 were designed to be mixable in a water system. Actually, neither one of them follows the ID specifcation all that closely. You certainly couldn't say what the ID and OD of 4 inch pipe is unless you look at the spec.

Nevertheless, traditionally pipes have been specified as IDs. You can see that in steel and copper pipes, for instance. Tubing is OD specified, mainly so that compression fittings, which fit the outside of the tubing, will fit.

Flexible hoses don't really fall into either category in a convincing manner. Many are used in compression fittings, where ODs are the sealing surface, and others are used on barbs where the ID is the sealing surface. You really have to do your homework, and make sure the sealing surfaces of the tube or hose or pipe have proper fit.

[Doomer]

Yes, do your homework.

Last time I went into Home Depot with plumbing questions all I could find were brain-dead zombies who didn't have a clue. I was mainly looking for a barbed T and 2 guys had no idea what I was talking about. I finally found it on my own in the lawn sprinkler section.