jfw,

Here is my $0.02. Plan out your system first. Decide the type of heads and how many you will be using. Find out the head loss and flow rate of the heads. Add them up and you will see what your demand will be. You understand the principles just do the homework and the fog will disappear. One foot of water in height equals 0.433527 pound per square inch. So 70 ft of height requires a pump of 30.35 psi to just get to the lawn or garden edge. A normal impulse sprinkler system would require about 60 psi to throw water from the sprinkler in a pattern that minimizes the number of heads, zones and time of running the pump. Lower pressure more heads or more zones and pump running time. 20 psi is what a drip system would require not to burst the poly pipes and pop emitters. The good pump suppliers will have the pump curve for the pump they want to sell you. Pump Curves show the ft of head versus flow rate. By adding up all the head's flow rate in a zone you can estimate your demand flow rate. Add 70 ft plus 60/0.433527 give you 208 ft of head or 90 psi. for sprinklers and 50 psi for drip. Once you have your flow rate and pressure then size the pipe that gives a velocity of 5 feet/second or less(laminar flow). 600 feet is pretty long so there is some friction loss to be accounted for from the pipe and fittings(not much if the pipe size is correct). Let us know what your demand will be in pressure and flow. JMHO aloha

Well designing the sprinkler system is my major hang up. I want rotor sprinklers and the ones I am looking at only require 4gpm at 50-60psi. I would like to be able to run at least 4-5 of those at a time to cut down on the number of zones. The problem is, I can't figure out what the pumps can deliver to the sprinklers so I don't know how many I can run at once. I'd hate to dig up half my yard only to find out that I need 6 more zones because my sprinkler heads have a 3 foot stream instead of a 40 foot stream....or worse, spend $600 on a pump that can't pump enough water up my hill. If I go by the gpm ratings on the pump, I can run 7-8 of these at once up my 70 ft hill with no problems. If I go by the pressure requirements on the spinkler, I can't even run one. So which is it?

What you're saying is very similar to what I've read elsewhere. The Flotec guy did supply me with a pump curve today. However, I don't understand if they are talking about the 70ft of head to the top of the hill or the 208ft of virtual head required to operate the sprinklers.

I understand the flow requirements and I understand the pressure requirements. The thing I don't understand is how a pressure rating and a flow rating can be translated to mean the same thing without even mentioning pipe sizes.

jfw,

Here is what I suggest, but I don't provide a money back guarantee, Most rating of pump manufacturer's are optimistic by 20%. The 208 ft is not virtual, it is the physical height difference plus the pressure in feet of head that will drive the zones. Read the pump curves for 208 ft of head plus 20% or a total of 250 ft of head. It is better to have too much head than not have enough. Then find a pump that produces that head with the gpm plus 20%. In your case 5 x 4 gpm is 20 gpm plus 20% which comes to 25 gpm. Check out these pump curves for 3 submersible 4" pumps. At 24 gpm you will get 250 psi. If you use more heads less pressure head and less heads more pressure head. This may not be what you expected when you thought about irrigating your area. There are other ways to do things besides a submersible pump. Other ways are more prone to failure and higher maintenance over time but cheaper. That is why you ask three contractors for a price. Do most of the work yourself to lower the cost but you will get good local info from the proposals. Aloha

http://www.pumpsandtanks.com/Curve-Charts/30_gpm_curve.htm