i don't know the formula, but the PSI will be higher with teh irrigation hooke dup than with the pipe just dumping free. close off the end of it and put a simple pressure guage on the end. costs less than 15.00 for it, and you can use it elsewhere or leave it in place for later fine tuning.

if you jsut want to know the math behind it, post over in teh plumbing forum and lazypup can tell you.

Hi MikeBuild,

The approx. conversion factor for feet of head to PSI is 0.5, That is for every foot of head you experience the pressure is 1/2 that in psi. 10 feet of head equals 5 psi. If your tank is used for gravity flow and storage then your tank needs to be pretty high to get any real pressure. You might as well irrigate from your pump directly if the psi is better than the tank height. Hope this helps. Aloha

lehua13, i think he wants to know how much PSI he is getting to teh end, and he does nto knwo the PSI the pump can produce. if he knew produced PSI you method works in that he can subtract it and get the end PSI. but the problem is he knows the volume of flow in the size pipe, and need to figure out what PSI he is producing.

Can't be done. GPM and PSI are two different factors to the same equation. You can take a five gallon bucket and see how long it takes to fill up and then do the math for a minute (i.e. 5 gal bucket takes 15 seconds to fill = 20 gallons/ minute). PSI must be measure from a guage.

mikebuild, imagine a large water cooler with a spigot near the base. When the cooler is full the flow rate (gpm) is faster through the spigot. As the liquid level comes down the flow rate gets less and less. A 16 oz. cup will fill up faster when the cooler is full. Pressure (psi) depends upon the height (and density) of the liquid while gpm depends upon pressure and diameter of the spigot. There may be a formula to calculate psi from gpm only but I suspect that it will be too complex for me. I'd use a pressure gauge.

Hey Mike, I've been doing this for half my life and still don't know what all those previous responses were trying to say. If you got 34gpm at the pump, then the lift is irrelevent. You have 34gpm, period. On a good system design, you want to use no more than 75% - 80% of total flow. So @34gpm you should not design any zone to put out more than 25.5 - 27.2 gpm. Most all centrifugal pumps (2hp and smaller) top out around 37 - 42psi. Jet pumps run higher pressure, but less volume. At 34gpm I'm assuming you have a 1, 11/2, or 2hp centrifugal pump. So let's go on the low end and assume you have a plastic centrifugal pump(cast-iron pumps run slightly higher:approx 42psi) that runs at 37psi max. If you keep your zones small, as mentioned above, and use 11/4 pvc pipe, at 100' of pipe your friction loss is between 2.91psi - 3.87 psi loss. So at the valve you should have 33 - 34 total dynamic pressure. Just keep in mind to run large enough pipe on zones until you get to the last 2-3 heads on lateral lines. Good Luck, hope this helps.

what size pump would I need to run a hydaulic system at 150 mph I am using a 900 cc motor to run the system

What does psi and gpm stand for also what does psi and gpm mean?

Maria,

psi is pounds per square inch. A force(lbs) pushing on an area(square inches) of an opening. gpm is gallons per minute. Volume(gallons)pushed through an opening per time (minutes). Psi is pressure and gpm is a flow rate. Aloha