How far can I run a water line?

[RayCo]

Does anyone know if there's a formula of some sort where I can determine how far I can run a water line before losing all water pressure?

I want to install two outdoor hydrants. The run to the first one is about 110 feet from my pressure tank in my basement, and it's about a 12' increase in elevation. From there, I'd like to continue another 70' feet and have a second hydrant. This one is about 18' higher than the previous one, or about 30' total above the pressure source. Is this doable? Should I run 1/2" or 3/4" lines? I'm not sure how to determine these answers.

 

[ultrarunner]

Here is an example of 30' feet change in elevation...

Start with 100 psi and move water to point B, which is 30 higher than point A.

To find out how much pressure will be left after the elevation change, multiply the elevation change by the factor .433.

30 x 0.433 = 12.99 psi loss.

Thus our beginning pressure of 100 psi minus our loss of 12.99 psi means we have 87.01 psi left.

100 psi 12.99 psi = 87.01 psi

Friction Loss is determined by the type of pipe, number of bends, etc...

 

[Gary Fowler]

Pressure wise you wont loose any pressure if you ran the line 20 miles. Deadhead pressure would be the same as at the source (assuming the elevations were the same) but your continuous flow might just be a trickle if you ran the whole thing in 1/2" due to the flow restrictions from friction between the water and the pipe.


I run all my remote water lines in 1" then reduce at the hydrant to 3/4". That way you don't loose much flow to the 3/4 line. I have one line that is over 500 feet from the water meter and I cant tell any difference in the pressure or flow from the hydrant that is 10 feet from the meter. Of course I have 100+ PSI inline pressure from the meter.

 

[prichard]

30' h2o is about 13 psi. Unless you have low pressure at the source, what you really need to consider is flow. Will both be open at once? What is the max flow rate you require at each hydrant.

 

[lpigott]

Gary is spot on. I also run any underground lines in 1" to branch points. The cost is differance is minimal so there is no reason not to.

 

[RayCo]

Interesting. It sounds like 3/4" is better to run because of the greater flow volume. I'm not worried about needing massive flow rates, since these hydrants will be used just to fill up chickens' water dishes, water flowers, stuff like that.

From what I'm seeing, it seems that the larger the pipe, the better. My source pipe in the house is 3/4", so I assumed it doesn't make sense to increase the size for the run outside to more than 3/4". Or does it?

 

[repete]

Here is an example of 30' feet change in elevation...

Start with 100 psi and move water to point B, which is 30 higher than point A.

To find out how much pressure will be left after the elevation change, multiply the elevation change by the factor .433.

30 x 0.433 = 12.99 psi loss.

Thus our beginning pressure of 100 psi minus our loss of 12.99 psi means we have 87.01 psi left.

100 psi 12.99 psi = 87.01 psi

Friction Loss is determined by the type of pipe, number of bends, etc...

From a firefighter who taught hydraulics for decades to pump operators, the above by ultrarunner is an excellent post. I would add to this the friction loss at various velocities through the pipe:
PVC Pipes - Friction Loss and Flow Velocities Schedule 4

PVC - Friction Loss in Fittings and Equivalent Length

Gregg

 

[RNeumann]

Friction loss is real. You will have to know pipe type, number of fittings etc to figure it out. This “calculator” is very crude but will give you an idea. Depending on where you live the “poly” or HDPE may be common- that stuff doesn’t typically use fittings in the field which helps.

On-Line Liquid Friction Loss for any Pipe Size

The loss with height is much simpler. It’s roughly 0.5lb per foot of elevation gain- 0.433 is very close to exact.

For a rough idea it’s typical to run a 1” line to a typical house. Because of freezing issues and because pipe is typically cheap I run 1 1/4” for bigger lots/longer runs like yours. 1/2” is a no go and 3/4” is marginal.

For your friction loss calcs you will want to end with 50-60psi min at the end of your run. Above 90-100psi and you will want a pressure regulator. Your situation doesn’t seem like it would warrant that though.

 

[Creamer]

Where I grew up we had a 1" poly water line that ran 1.5 miles with no appreciable loss of flow or pressure - elevation did not change much. Watered 200 head of cows with it continuously. We did have three large tanks to buffer the surge demand of herd mentality though.

 

[RayCo]

I love this site. So, this all makes sense. And, if I'm understanding things right, I might actually be better off running a one inch line, even though the main line coming out of my pressure tank in my house is only 3/4". True?