well pressure setting for sprinkler system? help!

16 years ago

I am installing a sprinkler system over 2 acres and need help making sure the pressure is optimal on my water well. I am using the well exclusively for the sprinkler. It is a great well (plenty of water), has a 5 HP pump, and 2 pressure tanks (one big and one small, maybe 50 gal and 30 gal?), also has a 2 inch pvc pipe which I will reduce to a 1 inch line for the sprinkler main, I guess. The current static pressure (pressure reading with the water not running) is 45 psi. I seems all the sprinkler places want a higher psi to be able to place the most heads on each zone. I need help. Do I need to increase the pressure in the tanks? Is there another pressure setting on the pump I need to make sure is an optimum setting? Also, the line leaving the wellhouse is between the well and the pressure tanks. Should I move that to the other side of the pressure tanks or does it matter? I need to start the sprinkler system install within the month. Any help would be greatly appreciated!--chad.

Comments (2)

mikie_gw
16 years ago
I forget gpm on 2 inch and you've not given the whole picture .... 45 psi sounds like that is where your pressure switch turns off the pump. How long that 2 inch and 1 inch is ... and how many fittings,,, is important.

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Waterit
16 years ago
1. The 45 PSI mentioned is what the cut-off is set at on the pressure switch. Boost this to at least 60 and make the cut-in 20PSI lower than that. With the system de-pressurized (off and drained of water), verify that your tanks have 2 PSI LESS than the cut-in pressure. Add air with compressor or bleed some off, as case may be. Tanks may be connected anywhere on mainline - closer to well is better for convenience/service. Install a glycerine-filled pressure gauge on the mainline near the tanks to help you check the settings.
2. Don't reduce to 1" for your mainline - it must match the output of your well. I'm going to assume it's a 5HP/90GPM, so you should be using 2-1/2" for a main.
3. The higher pressure isn't to be able to use more heads, it's so that the heads will actually pop-up and turn. High pressure can make up for low volume; the same is not true vice-versa.
4. Balance your zones to +/- 10% of flow (total GPM of heads on each zone) and adjust your pressure switch so that the pump will stay ON even when on your smallest zone. Pump should be either running or off, not cyclcling on-and-off.
5. Be sure to install pressure-relief device in case pressure switch fails - believe me, it happens.
6. I'd suggest ONE larger tank as opposed to the two small ones - ask your local pump supplier ot electric motor shop to size one out for you.

BK