How much water in a copper tube?

I am putting a tankless gas water heater in my home. All of the copper is in the concrete slab so I am going to run an insulated copper tube "up and over" to the kitchen. The water heater will be a foot from the two bathrooms and showers. the "up and over" tube will feed the kitchen sink and dish water - nothing else.

How much water is in a 100 foot by 1/2 inch copper tube? How much water is in a 100 foot by 3/4 inch copper tube? How much water is in a 100 foot by 1/4 inch copper tube?

I am too lazy to look it up - I am wondering if any of you experts on here have the info off-hand. I am thinking of putting thinning tubing to the kitchen because less water would be in it to cool down etc.

Right now I am running two 50 gallon electric water heaters in a house for two adults - I am wasting alot of energy keeping all that water hot

- and the tanks are far away from where the hot water is needed anyway running thru a cold concrete slab.

Harry

Reply to
Harry Everhart
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I found a formula for the different sizes on google.

Reply to
G Henslee

ID x ID x .7854 x length = volume

[231 cubic inches = 1 gallon = 128 ounces]

Rich

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Reply to
RICARDO AQUINO

I made up a little spread sheet. It assumes 1/32" wall on the pipe.

OD ID Area cu-in cu-ft cu-ft per ft per ft per 100 ft

0.500 0.469 0.173 2.071 0.001 0.120 0.750 0.719 0.406 4.869 0.003 0.282 0.250 0.219 0.038 0.451 0.000 0.026

I had to replace the copper pipes in my slab. I ran the new ones in a channel chiseled in the slab to get passed doors. For the heating system, I used 3/4" thick-wall copper pipe and wrapped it in duct tape to prevent future corrosion. The fresh water runs are 3/4" to laundry and kitchen, and 1/2" for the rest. The run to one bathroom is approximately 75 feet. It takes about 30 seconds to start getting the hot water at the end.

Reply to
William W. Plummer

Pipe is measured by ID, not OD. Tubing is measured by OD.

Wayne

Reply to
Wayne Whitney

Dear William - Thanks for the chart. I appreciate all the work. Does that mean 100 feet of 3/4 inch holds .282 gallons?

1/2 inch holds .120 gallons? 1/4 inch holds .026 gallons? I expected 100 feet of pipe to hold so much more. Harry
Reply to
Harry Everhart

(ID/2) x 3.1416 x (pipe length)

Just guessing.....

tom

Reply to
The Real Tom

(ID/2)^2 x 3.1416 x (pipe length)

Sorry to square the radius.

So should be radius squared times pi times length of straight tube.

hth,

tom

Reply to
The Real Tom

Yes, we do.

Reply to
Edwin Pawlowski

No. That's CUBIC FEET. Gallons per 100 ft are: 0.9, 2.1, 0.2

Reply to
William W. Plummer

LOL. I was somewhat surprised to see Harry get all of the help he did get, after that remark. Now. Who's he going to get to do the work? ;o)

... This is a good group of people.

Reply to
G Henslee

Not a good guess. The formula is A = pi * radius SQUARED, not pi * radius / 2.

-- Regards, Doug Miller (alphageek at milmac dot com)

Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?

Reply to
Doug Miller

People can sense honestly. :-)

I really like this group - no one ripped me - and I got great answers. Now I must decide whether I want to run 100 feet of 1/4 inch - 1/2 inch

- 3/4 inch to a kitchen sink and dishwasher 100 feet away from the tankless water heater. The tube will be overhead and insulated.

Opinions on that?

Harry

Reply to
Harry Everhart

That is a common misconception Try taking a ruler to 1/2" nominal Schedule 40 pipe sometime.

Pipe of the same nominal size is the same OD regardless of schedule, but the nominal size is always less than the actual OD, and usually less than the ID too. It may be that the nominal sizes were established by taking the ID of schedule 40 pipe and subtracting some nominal allowance for accumulated scale but I have never seen that in writing anywhere.

However tubing IS measured by the OD and the nominal size is the same as the OD.

Reply to
fredfighter

Like you, I am to lazy to look it up, but 1/4" will not provide much volume of water. Use 1/2" or 3/4" so you dont have to wait 1/2 hour to fill your sink. And since you are going overhead you can insulate the pipe at the same time. You may experience water hammer with the 1/4" also.

Reply to
Burnt Eddy

1/2". 1/4" is too small, and anything bigger is un-necessary. How much output can the heater keep up with, anyway?
Reply to
Goedjn

this thread is sad.... thank the american public education system.

randy

Reply to
xrongor

Refigeration tubing is ID, Plumbing pipe is sized by OD.

Reply to
Bob Pietrangelo

8 gallons per minute of 150 degree hot water. It will sit on the outside wall of my bathrooms. Since it is outside - no stack is necessary. Just water in - water out - 110 volt to run the computer and igniter. When no water is being drawn - no fuel is being spent. Harry
Reply to
Harry Everhart

Good point Eddy. I think I will just buy a coil of 1/2 inch flexible copper and run that from the tankless water heater to the kitchen sink. The dishwasher gets its water from the kitchen faucet tap. Harry

Reply to
Harry Everhart

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