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Nominal Ball Valves and why you need to know what that means


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This is Eric from FlexPVC.com

We've learned 99.9% of all aquarium people are very specific on their tanks. They go to a lot of expense and effort to get them just perfect. But there is a common mistake amost everyone has in their system: Nominal Ball Valves. Aka, MIP (Molded In Place) ball valves.

Why is it a mistake? What does Nominal mean?

Nominal means "in name only." For example a 1/2" pipe is not 1/2". Just like at the lumber store a "4x2" is not a 4" x 2". Those are nominal names. A 1/2" Sch 40 pipe is almost 5/8" ID (inside diameter) and almost 7/8th OD (outside diameter.) So why do they call it 1/2"? Just tradition. It's about 1/2", but the tolerance is the OD not the ID. Confusing, I know.

Just like a 4x2 (lumber) is 3.5" x 1.75".

So what does this have to do with Nominal Ball Valves? Well they are worse. A 1/2" Nominal Ball valves is WAY LESS than 1/2" ID. It's about 7/16". A 2" Nominal Ball valve is about 1.5" ID. If you don't believe me, go look at some.

I made a video showing this and put in on youtube along with a solution:

(basically if you want a full flow ball valve, you buy the next larger size and use reducer bushings to take it back down to the size of the pipe you want to us.)

I hope you found this informative. :-) And now you may know why your 1000gph pump really isn't putting out 1000gph... (well actually that's a whole 'nother post.... )


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