Jet pump to Fertilizer Injector-Pump Cycling Issue

**orchidherder** · 08-30-2010, 04:04 PM

Hello,
We have a deep well into the florida aquifer that feeds our entire 12 acre nursery-home-farm; We predominately grow orchids; The deep well feeds into a 500g aerator and is then pumped by a 1 HP sta-rite jet pump into one of our 8600sf orchid greenhouse; each zone in the house produces between 14 and 18 GPM depending upon the zone. We have a fertilizer injector that is max capacity @ 20gpm. So i cannot increase the size of the zones. The pump is currently cycling on 20-30 second intervals. There is only one pressure spring on this model pump(as opposed to many that have the 2, the one acts as the). Should I loosen the spring? tighten up on it? Or is there another option? If i didn't have to run the injector to medicate the plants this wouldn't be an issue, as i can just increase gpm with larger zones; the next size up, a 40 gpm Injector is almost $700. Any help would be tremendousl;y appreciated!
thanks,
tom

**ballvalve** · 08-31-2010, 06:41 AM

You can try and tighten the spring to increase pressure and perhaps keep it running. You can also valve down the outlet with that idea to match the flow and pressure needs of the feed lines. Or remove the switch and add a better standard pressure switch by square d. If you have a pressure tank in this setup, you could look at a csv valve too, which does automatically what tinkering with flow and pressure may accomplish.

**valveman** · 08-31-2010, 06:52 AM

You can increase the setting of the pressure switch by tightning on the adjustment screw. If you get the pressure above 56 PSI, say 40/60 pressure switch, that pump should not cycle if using more than 10 GPM. Just don't turn it up to much. That pump will dead head at about 68 PSI, so you don't want to get anywhere close to that. Or you can use a Cycle Stop Valve since that is exactly what it is designed to do.

**orchidherder** · 08-31-2010, 12:02 PM

thank you both! I really appreciate the instruction. This is one that had me awake late! I went ahead and tightened down on the spring, it was almost there, but still made that tell tale noise of being on the verge of d-heading; so i put a 1/2" line run before the valves/ injector, returning water back into the stock tank (500g) and one more line to an 8" drain pipe that drains into a pond. Presto! its working great!
thanks again!

hj · 08-31-2010, 01:05 PM

What you really need is a "storage tank" with a diaphragm, to balance out the pumps cycling. That would allow it to shut off when it reaches the set pressure and stay off until the pressure dropped to the "on" point, thus dampening the cycle times.

**valveman** · 08-31-2010, 01:50 PM

I just assumed he had a pressure tank since it was cycling every 25-30 seconds instead of 2 seconds. If there is already a tank there and the pump is cycing every 30 seconds, doubling the size of tank would make it cycle every minute. Four times the size of tank would cycle the pump every 2 minutes. No matter how big a tank you use it is still going to cycle. Dumping and wasting the excess water as he is now, or using a CSV would keep it from cycling at all.