Air Cushion versus Diaphram Tank Sizing

Al Roethlisberger

Quick question: If I have a 30 Gallon traditional air-cushion expansion tank, what is the formula to size an equivalent appropriate diaphragm tank?

Second question: Most specs for the diaphragm based tanks cite total volume and acceptance volume, which volume value is the one that I need to use the output of the question above to indicate the right size?

Thanks!
Al

Brad White_202

That is not a quick question, no fair!

Hi Al!

Truth be told, we rely on Taco Net to do our selections. OK secret is out But do give it a try!

Second question, it is the acceptance volume you seek. The entire tank in a diaphragm configuration is not usable for expansion.

Al Roethlisberger

Taco Net requires more info than I have


Heh, well I downloaded the Taco Net software, but unfortunately it asks for more info to calculate the recommended tank size than I have at hand, such as total system volume.

So since I already have the 30G "air cushion" tank "answer", does anyone know a conversion formula to "go backwards" and give me the correct acceptance volume for a bladder tank?

Thanks,
Al

Brad White_202

Al

e-mail me off-line tomorrow. I can send you a spreadsheet I developed to figure out volumes. Just enter linear feet by pipe size. I use this all the time.

In the meantime, I suggest that you try plugging in hypothetical numbers to see what sizing does.

If it is any help, my last two single family home piping systems held between 45 and 50 gallons, all told. At least that is a range, for what it is worth.