Need to know max GPH for a 2 inch diameter tubing, please. 1

[RumbleFish]

Hi,
I'm just a guy that is making a large pond with a waterfall feature.
I want to force the max amount of water into a 2 inch diameter pvc pipe.
PSI, friction and all else are not an issue, as I can buy very big pumps that are able to pump water at a rate of over 15000 GPH at a head of 35 feet. (My working head on this project)
With this in mind, please advise me of the greatest water volume I will be able to get from this diameter tubing
Thank you very much for the help
^_^

Spence

 

[hydrae]

Need to know how long the pipe is, if all you have is 30 ft then the 15000 gph is about right for friction loss (at over 25 ft/min), but minor loss will also play a big role and if you can buy big pumps why not buy bigger pipe?
Hydrae

 

[RumbleFish]

Not planning ahead...LOL.

I went ahead and purchased a roll of 2 inch tubing (100 feet) and cut it into 2 lengths of 50 feet, thinking I was going to have a T-split from the pump and use both pipes for the run on a single self-priming pump. I have since had a change of mind and I will be buying 2 pumps. One for each tube...... backwards, I know
Anyway, most pumps come with a 2 inch diameter discharge, VERY large pumps come with 4, 6 and even 8 inch discharge outlets.
So now I need to use my two parallel runs of 2 inch hose to there full potential when considering how much water I can shove through them.
Wishing I had bought 4 inch spiral tubing but it runs around $600-$700 for 100 feet. Hindsight is 20/20
BTW, my total run length is 50 feet and there is a vertical of 17 feet as well. Since each 10 feet of horizontal friction is equal to 1 foot of head (from what I have read), I believe I am working with a total of around 25 feet of head, 30 feet max.
Thank you for your response.

Spencer

 

[RumbleFish]

Anyone, please??

 

[hydrae]

Rumblefish

the 1ft of headloss per 10ft of lenght only works at one flowrate. The amount of water can flow through a pipe depends upon diameter, length, roughness, and differential head. As such if you want to flow 1000 gpm you can but it will take a lot of head. I have written the equation for friction loss from the Hazzen-William emperical formula to use in a spreadsheet. Put the following equation in your spread sheet cell a3, with the following titles

psid ft gpm c inches
loss length flow factor dia

=(4.727*B3*(C3/448.8)^1.852)/(D3^1.852*(E3/12)^4.871)*0.43

in b3 enter length, in c3 enter gpm, in d3 enter c-factor, and in e3 enter diameter.

C factor for plastic pipe is 130 to 140, Steel is 100 to 130 depending upon age.

and in a3 is the loss due to friction, play with the numbers. Remember your pump has its own curve and when the two meet in pressure is where the flow will be. The outlet diameter of pumps is typically smaller than the best discharge pipe size, so your original plan may not be so bad...
hydrae

 

[RumbleFish]

I think I can figure that out now, thanks for your help and time.

Looks like a good 2 HP pump with a high head will not have a problem forcing 180 GPM through the 2 inch diameter plastic pipe for a distance of 50 feet and a vertical lift of about 20 feet.
That's about the volume I want to have at the point where the water empties onto the top of the waterfall.

Do you feel that's a realistic and obtainable goal, that is getting 180 GPM to 200 GPM from each pump connected to it's own 2 inch pipe?

That would give me a combined flow from the 2 of around 360 GPM or 21600 GPH. Which will give me a great waterfall and a good amount of water for the stream that will run to the pond, which has just bee dug and waiting.......
Dim: 45'x17'x4' which gives me a water volume of close to 23000 Gals.

Thanks again
Spencer

 

[hydrae]

RumbleFish

Looks almost about right, 17 ft of loss through the pipe, and 20 ft differentail head, you will need to be in the 85% range on the pump for that flow and head, might be hard to find, you will probably get 160 gpm though.

Remember the equation I gave you gives the loss in PSID, if you remove the *0.43 at the end it will change to ft of head.

For horsepower hp=ft*gpm/3950/eff%
most pumps in the size you are looking at have a peak at 80% and normal operating range of 70% to 75%

Hydrae