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View Full Version : Well pump irrigation psi/flow question


country kid
05-30-2012, 01:49 PM
I would like to up the pressure at a well job that we just installed.

Details are as follows
5-6 heads per zone. 7 zones - All RB5004 rotors.
3/4" poly split with 1".

Each zone is matched to 14 gpm with nozzles. This keeps the pump from cycling.
At the pressure tank, the psi gauge holds at 57 psi without cycling.

If i nozzle the zones to 12gm, the pump will cycle every 3 minutes because it climbs to 60 psi because the cutoff is set to 60/40

My question is.
Can I up the cutout pressure on the pressure switch to stop at 70 or 75psi
, then nozzle the zones to be 12gpm and making the gauge hold at 66 or something?

Wet_Boots
05-30-2012, 03:25 PM
Just raise the cutoff to 70 psi and work from there - 70 psi used to be the max, based on range of adjustibility of switches, and the old standard of 75 psi tank ratings (with 5 psi safety margin, in case the pressure gauge was inaccurate)

Mike Leary
05-30-2012, 03:36 PM
in case the pressure gauge was inaccurate)

It's amazing how many pump houses I've walked into where the gauge was defective. I finally goaded my pump guys to install glycerin-filled gauges.

Wet_Boots
05-30-2012, 04:08 PM
I would give my own brand-new gauges about 5 psi leeway, just based on the usual gauge specs.

Also, note this specific advice is based on the existing cutout being 60 psi - raising the cutoff pressure without first draining the tank and raising its air charge is piker-ish, but a 10 psi bump is okay - a big increase in cutoff pressure should always be prefaced by adding to the air charge

DanaMac
05-30-2012, 04:20 PM
I've had some 100 and 150 psi gauges, that when spiked over their top end, were never the same again. I now try to get 200 psi gauges, since we have city water pressures exceeding 150 psi quite often.

Wet_Boots
05-30-2012, 04:35 PM
I think I've installed some 300 psi gauges.

Mike Leary
05-30-2012, 04:50 PM
griswoldwatersystems.com/pdf/GWS-1014.pdf

Wet_Boots
05-30-2012, 04:55 PM
I was always a US Gauge buyer, in part because I would need their 30 psi gauge to replace the frozen ones in the Toro flow&pressure gauge set.

Felco #2
05-30-2012, 06:50 PM
Is the well for irrigation only? If so, another option may be a smaller tank.

greenmonster304
05-30-2012, 07:05 PM
Is the well for irrigation only? If so, another option may be a smaller tank.

Why? That would make it cycle more often.
Posted via Mobile Device

1idejim
05-30-2012, 07:31 PM
Why? That would make it cycle more often.
Posted via Mobile Device

not quite so. the size of the tank is dependant on supply/demand. the smaller tank draw down is faster which turns the pump on. if the demand is just below or even to the supply, the tank won't fill to cut out pressure.

greenmonster304
05-30-2012, 07:41 PM
If only the tank was changed with no adjustments to the switch would it do the same thing only faster because the amount of draw down has been reduced?
Posted via Mobile Device

Wet_Boots
05-30-2012, 07:50 PM
Changing tanks isn't even remotely relevant to finding a higher steady-state pressure/flow point

1idejim
05-30-2012, 08:01 PM
Changing tanks isn't even remotely relevant to finding a higher steady-state pressure/flow point

who said it was? i just answered the question posed. vfd and constant pressure systems use 2 - 7 gallon tanks because thay don't depend on storage volume, they are designed to allow for the single glass of water use without avtivating the pump.

txirrigation
05-30-2012, 08:05 PM
I would like to up the pressure at a well job that we just installed.

Details are as follows
5-6 heads per zone. 7 zones - All RB5004 rotors.
3/4" poly split with 1".

Each zone is matched to 14 gpm with nozzles. This keeps the pump from cycling.
At the pressure tank, the psi gauge holds at 57 psi without cycling.

If i nozzle the zones to 12gm, the pump will cycle every 3 minutes because it climbs to 60 psi because the cutoff is set to 60/40

My question is.
Can I up the cutout pressure on the pressure switch to stop at 70 or 75psi
, then nozzle the zones to be 12gpm and making the gauge hold at 66 or something?

There is a nut/washer that holds down the spring on the pressure switch, give it 5-6 turns and it will up the shut off pressure. Check it by cycling the pump. Make sure you are operating within pump specs, if the pump is not designed to push that kind of pressure you will shorten the life of the pump.

Wet_Boots
05-30-2012, 08:08 PM
No, no, no, no, no. The OP is not touching anything but the pressure switch on an existing conventional pump setup in the basement of the client's home. (or so the smart money says)

1idejim
05-30-2012, 08:51 PM
If only the tank was changed with no adjustments to the switch would it do the same thing only faster because the amount of draw down has been reduced?
Posted via Mobile Device

possibly not, the recharge is dependent upon the demand V supply. if the demand is equal to the supply, the tank will not recharge until the demand subsides, at that point the supply is greater than the demand and the pressure tank fills to cut out pressure.

most all tanks work that way. :)

greenmonster304
05-30-2012, 09:01 PM
I know but he said his problem was he wasn't using the total output of the well so it was cycling.
Posted via Mobile Device

Wet_Boots
05-30-2012, 09:10 PM
A good designer can run a deep well submersible without a pressure tank, if need be.

1idejim
05-30-2012, 09:32 PM
A good designer can run a deep well submersible without a pressure tank, if need be.:clapping::clapping:
boots is a well versed pump guy, when he kicks a straight answer out he's usually dead on.

it's my view that workable hydraulics be designed into a system rather than altering the pump to make the system work. that's why testing the draw down and historical water tables are so important. thanks kiril :waving:

txirrigation
05-30-2012, 09:46 PM
No, no, no, no, no. The OP is not touching anything but the pressure switch on an existing conventional pump setup in the basement of the client's home. (or so the smart money says)

Your right, I saw pressure switch and assumed... assumed wrong.

country kid
05-30-2012, 09:47 PM
thanks for all the responses.

zones nozzled to 14 gpm keeps pump from cycling. It holds at 58psi constant without ever reaching 60psi.

there are 4 zones that are quite far from the pump. these 4 zones run o.k but not up to my standards.

Someone mentioned that a couple turns on the pressure switch cutout nut would up the pressure. This is what I want to do.
I am unsure that if I nozzle the zones to 12gpm that the psi will hold at 65psi without cycling.

I am not too sure but I would think that cycling the pump would shorten the life more than running at a higher psi.correct me if wrong.

country kid
05-30-2012, 09:48 PM
I will be touching the pressure switch and also touching some heads to change out nozzles to lower flow to up pressure

Wet_Boots
05-30-2012, 09:56 PM
If you get into situations where you can't prevent cycling unless the cutoff pressure is amped way way up, then things get complicated, but if you're lucky, you don't have to sweat any of that.

country kid
05-30-2012, 10:03 PM
i hope i never have to sweat any of that.
What would I do if he wants a zone of drip that is using only 6gpm.
Will cycling the pump for an hour everytime the drip runs shorten the life of the pump dramatically?

Wet_Boots
05-30-2012, 10:28 PM
Drip on a well could be done with discrete emitters. Pick oversized ones, and you can match the well output. Another tack is to use lowest-flow emitters, and get a low-flow zone that can run concurrently with a lawn zone.

country kid
05-30-2012, 10:31 PM
excellent response, thanks.

Sprinkus
05-30-2012, 10:37 PM
I've done combination pressure switch/pump start relay systems where the well/booster pump runs both the irrigation and house.
Not at all difficult to wire into an existing setup.
This way the house stays an on demand system and the irrigation is a pump always on when the irrigation is on system.

Wet_Boots
05-30-2012, 10:40 PM
Also, a low-flow drip zone could run by itself, and the cycling would not be an issue on a home well-water setup, because several minutes would pass between cycles.I've done combination pressure switch/pump start relay systems where the well/booster pump runs both the irrigation and house.
Not at all difficult to wire into an existing setup.
This way the house stays an on demand system and the irrigation is a pump always on when the irrigation is on system.This I never liked, because a stuck-closed valve or broken wire has the pump dead-heading into the relief valve, which is never plumbed to send the discharge out of the basement.

greenmonster304
05-30-2012, 10:43 PM
Drip on a well could be done with discrete emitters. Pick oversized ones, and you can match the well output.

I did that for this http://www.lawnsite.com/showthread.php?t=361783 because I had to water just a few trees and use up 12 gpm or the pump would cavatate.
Posted via Mobile Device

jabbo
05-31-2012, 07:06 AM
My sprinkler system/home runs off a well that produces about 13 gpm. And I do have a drip zone that has around 120 emitters. But that still is only 120X1 gph = 2 gpm if my math is correct. So its going to take alittle while for those 2gpm to make the well come back on. But I only run my drip zone about 15 min. so the cycling is really no more than the washing machine,dishwasher, or taking a shower does to the system or atleast thats the way I see it....

Sprinkus
05-31-2012, 08:21 AM
a stuck-closed valve or broken wire has the pump dead-heading into the relief valve, which is never plumbed to send the discharge out of the basement.

Yup, in a situation like that a flow switch (http://www.watts.com/pages/_products_details.asp?pid=685) would need to be installed to keep the pump from dead heading and activating the relief valve.

Kiril
05-31-2012, 08:31 AM
Drip on a well could be done with discrete emitters. Pick oversized ones, and you can match the well output. Another tack is to use lowest-flow emitters, and get a low-flow zone that can run concurrently with a lawn zone.

Keep a pump from cycling is not a good reason to use discrete emitters. Discrete emitters is why drip has a bad name. A good designer can build a drip zone without resorting to discrete emitters that won't kill a pump.

Wet_Boots
05-31-2012, 08:54 AM
Keep a pump from cycling is not a good reason to use discrete emitters. Discrete emitters is why drip has a bad name. A good designer can build a drip zone without resorting to discrete emitters that won't kill a pump.Keeping a pump from short-cycling is the overriding concern. Discrete emitters are not a problem if you can do a textbook install with adequate mulch cover, and they allow for visual confirmation that the water is actually being delivered.

Kiril
05-31-2012, 08:59 AM
Keeping a pump from short-cycling is the overriding concern. Discrete emitters are not a problem if you can do a textbook install with adequate mulch cover, and they allow for visual confirmation that the water is actually being delivered.

IMO, discrete emitters is what hacks and HO's use.

Wet_Boots
05-31-2012, 09:23 AM
I'm sure Rainbird will recall all their Xerigation manuals, based on your pronouncement.