# Pex tubing water amount??

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Larry4, Dec 3, 2008.

1. ### Larry4New Member

Joined:
Dec 2, 2007
Does anyone know how many feet of 1/2" pex does it take to hold 1 gallon of water?? kinda crazy question but cant fig it out..

Thanks

Lar

2. ### seaneysNew Member

Joined:
May 8, 2007
Location:
Chicago Suburbs
Well, a quick scan if sites indicates the ID is 0.475 inches...

The volume would be Vpex = Lpex * Pi * (0.457)**2 / 4...

I do not recall the number of cubic inches in a galllon off hand.

Stee

Joined:
Dec 12, 2005
Occupation:
Geologist
Location:
Knoxville, Tennessee
1 cubic inch is about 0.004 gallons. To answer the original question, it would take about 118 feet of 1/2 inch pex to hold 1 gallon of water.

Last edited: Dec 3, 2008
5. ### 99kRadon Contractor and Water Treatment

Joined:
Aug 16, 2008
Occupation:
Contractor of Radon Reduction, Testing, and Water
Location:
Fairfield Co.,Connecticut
a=3.14*.24*.24
a=.181 sq in

1 gal= 231 cu in

231/.181 = 1276 inches or 106 ft of pipe

Joined:
Dec 12, 2005
Occupation:
Geologist
Location:
Knoxville, Tennessee
Made me check my math. Using an ID of 0.457 inches, 106 feet of pipe would hold about .9 gallons. Try recalculating without rounding the pipe radius or pi and you'll get something closer to 118 feet.

larrygman - out of curiosity, why to you ask?

Last edited: Dec 3, 2008
7. ### 99kRadon Contractor and Water Treatment

Joined:
Aug 16, 2008
Occupation:
Contractor of Radon Reduction, Testing, and Water
Location:
Fairfield Co.,Connecticut
Hey Sam, the numbers are close enough for me I used a pipe I.D. of .475 (rounded to .48 ) which was given ... I did not actually measure it.

Joined:
Dec 12, 2005
Occupation:
Geologist
Location:
Knoxville, Tennessee
Everybody's a winner...

So I got to work and pulled a spec sheet for Zurn pex. The i.d. for 1/2" pex is given as .475 inches (118 feet) with a fluid capacity of 0.0092 gal/ft (108 feet).

I suppose the correct answer is that if you need something to measure a gallon of water with, don't use small diameter pex tubing

I think I'll be better off when things pick up a bit and I stop spending time on such trivial matters...

9. ### 99kRadon Contractor and Water Treatment

Joined:
Aug 16, 2008
Occupation:
Contractor of Radon Reduction, Testing, and Water
Location:
Fairfield Co.,Connecticut
Yes, this is a sure sign that both of us have too much time on our hands

10. ### Larry4New Member

Joined:
Dec 2, 2007
Thanks for all the info. I was asking because I am installing a pex floor system in an addition. I wanted to check the amount of water in the tubing to make sure I have plenty of capacity in the storage tank. This is my third and largest job of this kind. The others have worked out fantastic. I have installed them with a water heater where the customer doesnt have a boiler. Of course all the bells still have to go on pump, expansion tank, relay kit on and on. but in the end they are working great.

Thanks ,

Lar