New to this so bear with me;

Q1 2" piping will be fine as it will handle more water than you will need. Use the less expensive pipe, at 40 psi you will not have problems with high pressures. I dont think your loss of 1 psi over a 200 foot section can be accurate, should be more, if you can loop it then you can reduce your friction loss by 1/2.

Q2 Look for a lower psi loss if possible, the less, the better. Otherwise, accept the loss.

Q3 Filter is a very good idea, you can never know what you may be pulling through your pump.

Q4 Check your sprinkler specs, they should let you know if 33 psi is sufficient (check your long runs for true friction loss, though).

Thank you for approving/redirecting my plan. Please let me ask you about the second item, Pressure Drop across Valve. According to Stryker's Irrigation Tutorial, a solenoid valve shall be selected for 5 psi loss, for this pressure drop is necessary for valve closing. He even suggested dropping the valve size from line size by one step (if line is 1.5", use 1" valve), if one has to guess.

I called a local nursery irrigation supply store and asked about this. They didn't know a thing about downsizing valve by one.

Please comment.

Thanks.

fwiw;
I have hunter's pgp' rotors and as they come up to pressure, any kind of breeze blows their stream easily, far off path too sometimes. They run here at slightly over 40psi fine unless its real breezy. Much below that 40 they really stink in any wind.

I did 1hp jet pump and loss to heads is in the neighbor hood of under 2 lbs. Ovesized everything ... yep it takes a few minutes for a zone to come up to pressure. Pipes hold a lot of gallons. I shot for 2.5 ft/sec max and flow is probably less in more than not.

I think your starting pressure # is too low.

If you have a well capable of producing 50 GPM (which is doubtfull unless the well pipe, not the casing is at least 2") you will be able to get more than 40 PSI. Most wells are set up to maintain 60 PSI or better.

When designing a system you must know the GPM of the well. Isolate the pressure tank from the pump, and measure the output from the well for about 20 minutes. Make sure you have a constant output. Some wells start off at full output, but the sand won't keep up with the pump and you end up sucking air tward the end of the cycle. This can be accounted for with a good irrigation controller, but you need to know about it before it costs you $4000 in well parts.

I would worry more about GPM than pressure at this stage. You can boost pressure without much trouble.

Design your zones to use as close to your GPM water output as possible without going over. This will lengthen the life of your pressure swithes, pumps and motors.

Thank you for the replies.
1) Starting pressure: Since the well is not dug yet, it's going to be prejections. But assuming I will get a free-flowing well like my neighbors (contrators say the same), I am going to have an aboveground spinkler pump, 1 1/2hp. Immersible turbine pumps can get esaily damaged by lightning in my area, according to my neighbor. It is limited by 45 psi shut-off pressure. So, 40 psi discharge pressure is reasonable.

2) I am not using a jet pump. According to the expert at the store I called, irrigation needs irrigation pump, not jet pump. Jet Pump can give pressure but cannot keep up with flow rate.

3) I am not usign a pressure switch or a tank. Again, according to the expert, irrigation needs a well and a pump. Don't use anything else, according to him.

4) Someone mentioned delta pressure of 2 psi at the sprinkler head. That is much assuring.

5) I am oversizing everything to minimize pressure drop. 2" lateral is an example. I really don't need this size.

6) Still, the valve pressure drop bothers me. I can see that there needs to be certain pressure drop across valve for proper operation (more for opening than closing?) But 4 or 5 psi? I am not convinced. I am going to use 1 1/2' valve.

7) In the worst case, I will go with microirrigation. (I am not watering lawn. I am watering plants, some in pots some in ground). That will cut down everything, pressure need and volume need. But I have to run black poly and 1/8 feed lines and micro irrigation heads.

Thank you for sharing your experiences. I would not have know about water stream blown by wind at 40 psi, for example.

You really have serious design flaws in this somewhere. That's the problem with Strykers tutorial. There are other factors that play in besides pressure in a system. Especially in systems fed by a well. He does a good job explaining theory, and keeping people from over building their supply, but sometimes you have to add things into the design that his step by step can not account for.

I would strongly suggest you call a local installer and at least get his recommendation regarding how to get your water.

There is NEVER a need for a 2" lateral line in a residential system. NEVER NEVER NEVER. Most sports fields don't use laterals that big.

Please excuse my lack of candor here, but you need some professional help. An "irrigation pump" usually is not designed to lift water from a well, even if it is "free flowing".

Before you spend thousands of dollars on this, get someone involved who does this for a living, even if you pay them a couple hundred dollars for consulting, you will save 10 times that!

2) I am not using a jet pump. According to the expert at the store I called, irrigation needs irrigation pump, not jet pump. Jet Pump can give pressure but cannot keep up with flow rate.

3) I am not usign a pressure switch or a tank. Again, according to the expert, irrigation needs a well and a pump. Don't use anything else, according to him.

I think this is where your problems all start.... Find a new expert that knows both wells and sprinkler design. You can use a relay to start the pump from the clock, but my experience tell me that you should use a jet pump and a small pressure tank to absorb shock, not to store water and a pressure switch set to kick on a 50 lbs and off at 80.

You should have a pretty good idea what your output from your pump will be at those levels by the specs provided by the manufacturer.

Thanks for the replies. Now I see the difference between sprinklers and microirrigation. The stores that I contacted were selling irrigation supplies to nurseries, where individual pots are watered through microirrigation. The expert opinions must have been for microirrigation. Thanks.