sprinklers problem

I installed new spriklers in my yard using a design from rainbird.com. My well produces 9 GPM with 50 PSI. I followed instructions from rainbird design, replaced the nozzles according to instructions and created 4 zones with 5 to 6 sprinklers each. None of the zones have more than 7 GPM. When I tested each zone everything worked as expected. I installed a timer but I have this problem: 50% of the time the sprinkler will not come up all the way. I have the same issue on all 4 zones, but as I said it happens 50 % of the time. I realized that if I manually open the valves twice everything is fine and the sprinklers come up fine. It seems to be an issue with the pressure (not sure, could be flow issue). I adjusted the pressure in my pump sta-rite sle 1 HP but I still have the same problem. If I use the timer some sprinkler won't come up and therefore won't work properly. It works fine if I open each zone by hand two time. How can I take care of this problem. Did somebody have this problem before? Thanks in advance.
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I would like to clarify that the problem is not the timer. If I completely bypass the valva and the timer and connect all the zones to the main valve, I still have to open it twice in order to get the sprinklers up. Also, once they are up, they remain up all the time w/o any problem.
Thanks again!

I have 50 rain bird sprinklers and at 50 PSI and 7 GPM they work no problem. (Oddly thats exactly what mine are configured for since my wells max output is 9GPM at 50 PSI.) They also pop up fine even at 35 PSI. Mine has 1.25 inch poly main lines with 1 inch poly distribution lines after each zone valve.

You are losing water volume somewhere. I'd start by disconnecting one of the zones from the valve, connecting a short piece of pipe, opening up the zone and checking that you are still getting something close to the 9 GPM you started with. If you are I would think that your distribution line is too small or your heads are consuming more water that you thought. The nozzles on the Rainbird rotors are removable so you could reduce the size of the nozzle if they are consuming too much water. If you aren't getting 9GPM I'd take a serious look at the backflow preventer and its associated piping.

-rick

gadan said:

My well produces 9 GPM with 50 PSI. None of the zones have more than 7 GPM.

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Since 9 GPM into a water system must equal 9 GPM out because water is incompressible and the pipes don't balloon, either you are losing 2 GPM somewhere or your well pump curve should show some pressure other than 50 PSI at the 7 GPM value.

Pipes drop the pressure. A 1" pipe at 6.3 GPM should drop 1.1 PSI for each 100'.
http://www.engineeringtoolbox.com/pe-pipe-pressure-loss-d_619.html

With the pump curve, more GPM delivered results in less pressure. The piping is the load on the pump, and the "pipe curve" is the opposite of the pump curve; more pressure at the pipe inlet means more GPM into the pipe.
The intersection of these two curves is your 'operating point.'

BTW, how deep is your well?

Thanks for your replies. My well is 84 feet deep. Rainbird design recommended 3/4 sch A pvc pipes and that's what I installed. I reduced some of the nozzles from 1.5 GPM to 1.0 and still have the same issue. Went from 7 gpm to 6 gpm in one of the zones and the problem remains the same. Sometimes sprinklers pop up fine, sometimes don't, then close the vale and open again and everthing is fine. I did the test again and still get 9 gpm from the valve that the zones are connected to.

I'm thinking THATGUY is on the right track. It sounds like your well's pressure switch is set to 30-50. 50 is fine for sprinklers, unfortunately 30 sucks. More on that in a minute.

You say the rotors pop up fine sometimes. Thats because by chance the pressure tank is charged to somewhere near 50 PSI. Even if your system pressure drops now the rotors will stay up because it takes much less pressure to keep them up then it does to pop them up.

The times that they don't pop up your pressure tank is charged below 40 PSI because maybe you flushed a toilet or used a sink and drew some water out of the tank, but not enough to cycle the pump on. (your manually turning on the system, and then off again triggers the pump to come on and build pressure so when you turn it on the second time you have enough pressure built up to pop up the heads) So when your rotors come on and the pressure is 31 PSI, ideally the pump would cycle on and build pressure to over 40 PSI and your rotors will pop up all the way, maybe a bit delayed but they would pop up. In your case it sounds like the pump is unable to build pressure back up to 40PSI. If you can't maintain 40 PSI with the rotors on, well, you've got yourself a real problem. You need to have less rotors on a zone. (This is a problem with sprinklers on a well. Knowing your static pressure and your GPM is not enough to build a system. You need to know how much water you can get at a constant 40PSI or better. You seem to know what type of pump you have. Can you find or do you know the pressure curve for it?? )

Okay, back to what I was saying about 30-50 pressure switches sucking for irrigation. Adjust the pressure switch limits to 37-57. That is probably the max you will be able to adjust it to. See if that fixes the pop up problem.

Also make ABSOLUTELY SURE your pump can build pressure to 57 PSI to reach cutoff both initially and after you have run your irrigation system. If it can't you cannot use 57 as your top limit. Your pump will burn up in a matter of minutes if it can't reach cutoff when no water is being used. If you intend to leave it at 37-57 you need to add air to your pressure tank for the best pump performance (see sticky at the top of the well forum on how to do this).

Even if this fixes the pop up problem running the irrigation system on less than 40 PSI is less then ideal even if it seems to work. I would increase the pressure switch settings and decrease the number of rotors on a zone until I could achieve a constant 40 PSI or better.

-rick

Thanks Rick for your excellent response. We use this well just for irrigation. There is a gauge in the pump showing 50 PSI, when pump is on PSI goes up to 60. I will check the website for the sta-rite pump and see how to increase the pressure and remove some rotors as you recommended.
Thanks again!

Before making any change and removing some rotors from my zones, I would like to know if is possible to install something outside my sta-rite pump to improve PSI. I heard that some companies install a pump booster. Does anybody know about this pump booster? Is it worth to do it? I appreciate your inputs.

Gabe

The only thing that can boost pressure is another pump like a dual stage pump. However if your well only supplies 9 gpm you can't increase the pressure vs volumn with any pump. Only what can get in will get out. I don't see that a larger pump or another pump would help in your case.

If you aren't getting the desired pressure while a zone is running I suspect that the heads are demanding more water than the pump can supply.

Read my stories by Googling "Porky's Hole Thoughts"

You need a delay between zones. If your controller doesnt have this feature, skip a zone when wiring them. Aka connect zone one leave two black connect three etc.. Many times when running a well, the zone changes is what causes the problem. When switching from zone one to zone two zone one is running (at say 7gpm) then for a few seconds zone 2 comes on (demanding initially double its flow rate to fill the lines). This draws down your pressure tank and the pump isnt able to catch back up with this cycle as the zones continue to operate.

Many times ive set a delay between stations to keep this double demand from happening, and also allow the pressure tank to fill up between zones. Its saved many a customer from installing a larger pump.

Good luck!