Piping size versus total output

[AlexDring]

Is there a simple way to calculate how much water a pipe will transfer at given PSI's? Nothing too accurate for right now, just trying to get an idea how big a pipe roughly should be to get costs. In detail, how much water in gpm, will go threw a one inch pipe at 30, 60 and so on in psi. All pretty much flat, with the pump not selected yet. Any help would be appreciated.

Alex

 

[TBP]

For looking up bits of information when you're in a hurry, or just to ballpark something (like your problem), there are two little softcover books I find very useful - "Pocket Ref" by Glover, and "Handyman In Your Pocket" by Young & Glover. They have (among lots of other things) tables and formulas that will answer your question. The "Handyman..." has tables for all kinds of pipe material, and has a section on pumps, too. These books are pretty easy to find - I found my copies in hardware store checkout line display.

 

[htsmech]

Lots of websites on this, here is one.

http://www.efunda.com/formulae/fluids/calc_pipe_friction.cfm

See the hint to calculate a flowrate below the inputs, or find a website that has a calculator that has output pressure as an input, or just use the equations to plug and chug.

Good luck,

Steve

 

[gramya]

I hope that the flow quantity is more related to the allowed velocity in the pipe. A water velocity of upto 10ft/sec in noncritical application shall give you the flow.
Generally discharge lines to pumps are designed with 6-8 ft per sec velocity for long distance transfer of water. Your inlet pressure is therefore no consideration in the flow quantity calculations unless you have a defined pressure drop in the piping system.

Narendra K. Roy
Gramya Research Analysis Institute,
PO box 4016, Vadodara 390015, India
Website:

http://www.gramya.com

;

http://www.charismaglobal.com

 

[AlexDring]

My question was more for gauging what size of pump would be too much for one inch piping. Here is the breakdown of the question. I bought a old farm house a while back with a driven well. Built in 1935, no record was kept of depth of well or water. Therefore I have no way of knowing the total head and lift the existing pump has to do currently. The piping is around 1.5 to 2 inches od. The house is near a river, from which I am told the underground has big rocks and well recovery is not a problem. I do know by talking to my neighbors and reviewing there well logs, the water line is about 5 feet down and most wells around the area are 50-75 ft. If I found the max capacity of a pipe size, mainly my well, I would then know the limit in pump and motor size that my well could pump out.

So now I am ready to stick in a sprinkler system and I am doing the research. My current pump is a half horse centrifugal by Fairbanks Morse. It puts out a little above 5 GPMs at the faucet with only about 30 psi. So I just wanted to know what would be the max size of pump for that line of one inch. Since the house pressure is fine, but I just need more capacity on the sprinkler side.

This is my plan to date, anyone with advice, feel free to tell me otherwise. I plan on removing the half horse and replace it with a bigger motor and a jet pump to match. I was then going to split the discharge immediatly before the pressure tank. One going to the house with a regulator and the other going to the sprinkler main manifold and valves. I am not to keen on fluid dynamics but I know there is a way to run lines and not to run lines for each sprinkler to get the same pressure. Example: One station (zone) to have four sprinkler heads. One inch pipe branching off the one inch manifold, going to a junction. Where it would drop down to three quarters to each head with each line of three quarter equal in length. Am I correct or smoking my lunch, any suggestions.

 

[pmureiko]

Let's try and estimate what your water system looks like. But first not increasing the motor size will not increase the pump flow or discharge pressure. You must either change the pump diameter, add stages for multistage pump, or increase pump speed. Still forging on.

1) What is your pump head at 5 gpm assuming the pump needs all hp at 50% efficiency. The actual power requirement may be less as well as the efficiency.

1/2 * 1714 * 50% / 5 = 86 psi --> 199 ft of water

This is very likely a multistage deep well pump.

2) How deep is your well (x) subtracting supply pressure and friction in a 1" pipe. Assume 150' of distribution piping after well water is at grade.

86 psi - 30 psi - 0.85 (x + 150) / 100 = x / 2.31
54.725 = 0.424 x

x = 130 ft deep well. This is deeper than you neighbors, could their wells be 50 to 75 meters deep?

3) You can force as much water through a pipe as long as you have the head to overcome friction losses. Let's see how much water can be crammed through the 1" pipe with a 1 hp motor and maintaining a 30 psi system pressure. This is a system of 3 unknowns and 3 equations.

1 * 1714 * 50% / y = z
z - 30 - f (130 + 150) / 100 = 130 / 2.31

Approximately y = 9 gpm, z = 95 psi, and f = 2.6 psi/100 ft

 

[AlexDring]

Hmm that is interesting. I know the pump says SWP5, which I was informed by a near by pump show as Shallow Well Pump 1/2 (.5) horse. I wonder what I am doing wrong. Dang it.

 

[ElwoodGreen]

My well is 140' deep and a 0.5 hp pump was installed. Pipe size to the pressure tank is 1.25". The 80 gallon or so pressure tank is a "standard" set-up around these parts. The pump fills the tank every so often, depending upon usage. I have a few tees in the line to supply yard hydrants, and the line to the house is 1". I can easily get 25 gpm, which is what my well driller said it produced. However, this is an artesian well with about 8 psi at the surface when capped.

Only 30 psi in the house? I set my switch to run the pump at about 45 psi and shut off at 60 psi. I still get temperature fluctuations when in the shower and the wife turns on a faucet. I think the house plumbing is to blaim--is a mobile home.

Good luck!