Pipe Volume

Users who are viewing this thread

tel

New Member
Messages
6
Reaction score
0
Points
0
Can anyone tell me how to work out how much water a lengh of pipe will hold. What I want to know is, how much water will it take to fill 500' of PEX pipe.
Regards
tel
 
R

Rancher

Guest
Since you didn't give me the diameter of the pex pipe, you'll have to make the calculations yourself.

Pi x R squared x lenght (500' or 6,000")

Pi = 3.1415
R = Radius of the pipe, i.e. half the diameter.

So for 3/4" pex

3.1415 x (.375 x .375) x 6,000 = 2650 cubic inches

2650 / 144 = 18.4 cubic feet

18.4 X 7.48 = about 138 gallons (7.48 gal per cubic foot)

Rancher
 
Last edited by a moderator:

Mikey

Aspiring Old Fart, EE, computer & networking geek
Messages
3,024
Reaction score
17
Points
38
Location
Hansville, Washington
Don't forget to subtract the pipe's wall thickness when you compute the radius. PEX complies with SDR 9, so the wall thickness is 1/9 of the diameter. For 3/4" pipe, that's .083", so making this adjustment throughout, and using 1728 cu in per cu ft (thanks, jimmym) I get about 7 gallons.
 
Last edited:

tel

New Member
Messages
6
Reaction score
0
Points
0
Sorry about that.. 1/2 pex, I want to use it for underfloor hotwater heating system.
Thanks
tel
 

Mikey

Aspiring Old Fart, EE, computer & networking geek
Messages
3,024
Reaction score
17
Points
38
Location
Hansville, Washington
I need to go back to 3rd grade.

Correcting for lots of screwups, the real numbers are as edited (or as will be edited shortly) above. I think.
 
Last edited:

tel

New Member
Messages
6
Reaction score
0
Points
0
Thanks guys..
That was about what I thought.. My problem is I am thinking of having underfloor hotwater heating system installed in my family room, and the contractor is telling me I need about a 30 gal elec hotwater tank, seems alot to me.. Any thoughts?
Cheers
tel
 

Mikey

Aspiring Old Fart, EE, computer & networking geek
Messages
3,024
Reaction score
17
Points
38
Location
Hansville, Washington
The problem is you're not just heating the 3, 7, 10, or however many gallons it might be. You're maintaining a flow at a desired temperature. Depending on the flow rate and temperature differential, you need a certain number of BTUs, which translates into a certain number of kVA, kwH, etc., which determines the size of the WH. There are a couple of guys here who can do these calculations off the top of their head, but they'll need more data than we have so far. The odds are your contractor has already done these calculations (ask him to explain) and determined the 30gal WH is appropriate.
 

Bob NH

In the Trades
Messages
3,310
Reaction score
9
Points
0
Location
New Hampshire
Before you look at gallons, you need to consider BTUs per hour.

How many BTUs per hour do you need?

Then you need a heater that will deliver that many BTUs per hour.

1 kW = 3413 BTU per our if you are heating with electricity.

If you are looking at a gas heater, then you need to look at the rating of the heater, usually in Net BTU/hour.
 

tel

New Member
Messages
6
Reaction score
0
Points
0
Thanks to every one that has replied to my question. it has been a great help.
regards
tel
 

hj

Master Plumber
Messages
33,600
Reaction score
1,037
Points
113
Location
Cave Creek, Arizona
Website
www.terrylove.com
heater

6 gallon, 30 gallon, or more is basically immaterial. You have to size it for the recovery, not the storage, so the energy input is what counts, not the size.
 

BubbaBob

New Member
Messages
1
Reaction score
0
Points
0
Location
N GA mountains
Make it simple and economical

I've just built a 706 sq ft yurt (google them...they are interesting) and for heat I installed radiant floor heating using a Takagi TK-Jr propane tankless heater. My floor has 700 linear feet of 1/2 pex-a in 4 zones, and the expansion tank is a 2.2 gal Watts, which is more than enough.

Inexpensive, economical operation, efficient, trouble free. What more could one ask for?
 

Gary Slusser

That's all folks!
Messages
6,921
Reaction score
22
Points
38
Location
Wherever I park the motorhome.
Website
www.qualitywaterassociates.com
I've just built a 706 sq ft yurt (google them...they are interesting) and for heat I installed radiant floor heating using a Takagi TK-Jr propane tankless heater. My floor has 700 linear feet of 1/2 pex-a in 4 zones, and the expansion tank is a 2.2 gal Watts, which is more than enough.

Inexpensive, economical operation, efficient, trouble free. What more could one ask for?
We already have 6 solar panels and 6 6volt AGM batteries BUT I'll ask for 2-3 more solar panels, 2-4 more AGM 6 volt batteries and a central vac system for my totally off grid motor home. Then I wouldn't have to run the generator at all. A yurt is immovable LIKE A HOUSE!
 

hj

Master Plumber
Messages
33,600
Reaction score
1,037
Points
113
Location
Cave Creek, Arizona
Website
www.terrylove.com
volume

And to mess up the original calculations, PEX i.d. is NOT 3/4". It is between 9/16 and 5/8 meaning that its volume is about 75% of copper tubing.
 
Top
Hey, wait a minute.

This is awkward, but...

It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.

If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.
I've Disabled AdBlock    No Thanks