Nominal Ball Valves and why you need to know what that means - Aquarium Forum
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post #1 of 6 (permalink) Old 07-21-2015, 06:44 PM Thread Starter
 
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Nominal Ball Valves and why you need to know what that means

Hello,

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". A 4x2 is not a 4x2. 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 putting in on youtube along with a solution:

https://www.youtube.com/watch?v=BZjCyGqDOwo

(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 use.)

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.... )

HTH

Eric
Flexpvc.com
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Last edited by FlexPVC; 07-22-2015 at 02:13 AM.
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post #2 of 6 (permalink) Old 07-23-2015, 10:32 AM
 
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Re: Nominal Ball Valves and why you need to know what that means

Good info. Thanks.

I'm OK using the nominal ones now because even with all my valves open my pump isn't strong enough to fill all tanks at the same time. But I'll keep it in mind if I ever expand and need a larger pump.
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post #3 of 6 (permalink) Old 07-23-2015, 11:04 AM
 
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Re: Nominal Ball Valves and why you need to know what that means

This is very helpful. Thanks for posting!
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post #4 of 6 (permalink) Old 07-28-2015, 06:23 AM Thread Starter
 
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Re: Nominal Ball Valves and why you need to know what that means

I did a table/chart to show the % loss of cross sectional area by using nominal ball valves. I think you'll be surprised by the effect:

#1 FlexPVC®.com Tech Article - Loss of flow due to the use of Nominal Ball Valves and why you need to know.
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post #5 of 6 (permalink) Old 08-24-2015, 02:13 AM
 
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Not that it changes the point that you're making but just so you know, a 2x4 is 3-1/2"x1-1/2" not 3-1/2"x1-3/4".
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