Pressure switch Kick-On point

[JustaDIYer]

Been trying to figure out why I'm having low pressure issues this year with my sprinkler system, never have in the past. Noticed pressure was down to 25psi or so while a couple zones were running.

So was doing a GPM test by filling a bucket from a full tank till the pump kicks on and then timing the cycle.

My pump kicked in at ~35psi (my switch is a 40/60 switch). I just recently checked my tank pressure while empty and it was at 38psi (I plan on rechecking it tonight as well).

Shouldn't the pump kick in at ~40psi and not 35? Should I adjust the switch to bring it back up to 40? The switch is relatively new, maybe 2 years old. Would this cause low pressure issues in sprinkler system?

 

[Reach4]

Gauge could be off.

When the water pressure is higher than the air precharge pressure, the water pressure and air pressure would be about the same. That is useful for comparing the two gauges.

To raise a common pressure switch from 35 psi to 40 (5 psi increase) kick-on, turn the nut on the big spring clockwise ( 5*0.35)=1.75 turns. That raise both the turn-on and turn-off Do not adjust the nut on the small spring (differential) under normal circumstances.

Or maybe go more. Turning 3.5 turns CW instead should raise the turn-on by about 10 psi, aiming for 45/65. In that case, raise the air precharge too.

 

[Sponsor]

 

[JustaDIYer]

ok, so adjust to kick on at higher pressure. and if I go to 45, adjust air tank to 42-43 psi.

I understand gages can go bad, this one was replaced at same time as the switch and read correctly when installed and is about same as the other 2 I have in system, post iron filter and post softener (minus a little to pressure drop). I'll double check those as well.

Would raising the kick in pressure help the sprinkler issue of them running at ~25psi at times?

 

[Reach4]

Would raising the kick in pressure help the sprinkler issue of them running at ~25psi at times?

More pressure will help generally. Note what the pressure gauge at the tank says when your sprinklers are not doing well, or is the 25 measured at the pressure tank? If that, your sprinklers are using more water than your pump can produce. Get smaller emitters for the sprinklers to balance with what the pump can do.

Does this well provide your house water too?

 

[JustaDIYer]

That's why I was checking my GPM, thinking that was the issue and I plan on changing out the heads as well. For the past couple years, I've replaced the heads with direct replacement so my assumption was that was ok and never had this issue prior. Change is the only constant I know.

Yes, same well provides house water and sprinklers. Wife mentioned she has noticed the pressure has been lower of late.

 

[Bannerman]

post iron filter and post softener (minus a little to pressure drop).

Comparing static pressure (while no water is flowing), all gauges should indicate indentical pressure. Pressure drop will only occur while water is flowing as the pressure drop seen after the softener is due to a restriction to flow through the softener.

Would raising the kick in pressure help the sprinkler issue of them running at ~25psi at times?

If the pump is becoming worn out or if the water level in the well is lower than usual, then the pump will move less water compared to previous. While increasing the pressure setting should normally improve the situation, if the pump can't keep up with consumption, then the pressure will drop to where the pump can satisfy consumption. A pump will deliver higher flow with lower head (less backpressure) compared to when there is higher backpressure.

As there is a noticable pressure decrease in the home, likely while no sprinklers are operating, this then suggests the issue is the pressure switch.

 

[Valveman]

You could also have a leak in the irrigation system.

 

[Reach4]

Yes, same well provides house water and sprinklers. Wife mentioned she has noticed the pressure has been lower of late.

1. Do you have a filter, such as a cartridge filter? I am wondering if that is plugging up.
2. Is the tee-off to the outside spigot before or after that filter?

When the pressure seems lower, while water is being used, see what the gauge at the pressure tank says.

 

[JustaDIYer]

Comparing static pressure (while no water is flowing), all gauges should indicate indentical pressure. Pressure drop will only occur while water is flowing as the pressure drop seen after the softener is due to a restriction to flow through the softener.


If the pump is becoming worn out or if the water level in the well is lower than usual, then the pump will move less water compared to previous. While increasing the pressure setting should normally improve the situation, if the pump can't keep up with consumption, then the pressure will drop to where the pump can satisfy consumption. A pump will deliver higher flow with lower head (less backpressure) compared to when there is higher backpressure.

As there is a noticable pressure decrease in the home, likely while no sprinklers are operating, this then suggests the issue is the pressure switch.

Yes, I assumed that was known. Statically the same and while water is running there are slight drops.

Pump was just replaced a couple years ago.

And no, I don't compare house usage while sprinklers are running. The decrease is while sprinklers are not running.

You could also have a leak in the irrigation system.

Had that thought as well, don't see anything that indicates a leak. I had one before and a big bubble appeared in that area.

1. Do you have a filter, such as a cartridge filter? I am wondering if that is plugging up.
2. Is the tee-off to the outside spigot before or after that filter?

When the pressure seems lower, while water is being used, see what the gauge at the pressure tank says.

No cartridge filter. The T for the sprinklers is before the filters. It is direct from the tank.

 

[JustaDIYer]

Turned up the switch, now 40/65.

Pull about 7 gallons of water with a full tank. Takes about a minute from pump kick on to kick off.

7gpm?! I'm thinking something is wrong.

 

[Reach4]

I am not sure why you would find 7 gpm surprising. Were you expecting more or less?

Is that 40/65 a typo? We were hoping for 45/65. You may want to do some re-jiggering, which would include loosening(CCW) the nut on the small spring (Differential), and then re-adjust the nut on the big spring (Range). The small spring is typically nearly loose to get to the 20 psi differential.

To raise or lower the cut-in and cut-out settings while keeping the
differential between those two settings constant, adjust the range
nut. The range nut is the 3/8-inch nut that adjusts the larger of
the two springs in Models FSG, FYG, FRG, and Type G Pumptrol
switches.
Turn the range nut clockwise to increase the cut-in pressure and
counter-clockwise to lower the cut-in pressure. Three and a half
revolutions of the range nut will change both the cut-in and
cut-out settings by approximately 10 psi.
Adjust the differential nut if you want to raise or lower the
cut-out setting while keeping the cut-in pressure constant. The
differential nut is the 3/8-inch nut that adjusts the smaller of
the two springs in Models FSG, FYG, FRG, and Type G switches. Turn
the differential nut clockwise to increase the cut-out pressure and
counter-clockwise to lower the cut-out pressure. Adjusting the
differential nut will change only the cut-out setting while the
cut-in setting remains unchanged.
​

Do you have a 32 gallon pressure tank, and what was the air precharge set to during your recent observations?

 

[JustaDIYer]

Last time I checked gpm I was over 10 I think (years ago on old pump). 7 seems low, no?

32 gallon tank set at 37/38psi empty.

I turned the middle screw to get 40psi. It was running at 35/60. Now it's been bumped up to 40/65 (same differential). With this I'd think if I went to 45 the upper would go to 70.

So I guess I need to adjust the differential screw, CCW a few rotations?

 

[Reach4]

So I guess I need to adjust the differential screw, CCW a few rotations?

Yes. Then you will follow up with range nut CW.

Note that once the water pressure is less than the air precharge when the pump is off, the water pressure drops very quickly.

Even with the same pump, it is reasonable that the gpm drops when pumping into higher pressure.

 

[JustaDIYer]

Ok. So CCW on differential screw to get 40/60?

Why do I need to adjust the range screw?

 

[Reach4]

Ok. So CCW on differential screw to get 40/60?

Why do I need to adjust the range screw?

"Adjust the differential nut if you want to raise or lower the
cut-out setting while keeping the cut-in pressure constant." So as you turn CCW, the current 40/65 turns to 40/60. Then to get from there to 45/65, turn range nut about 1.75 turns CW.

 

[Valveman]

Watch the gauge while you are experiencing low pressure in the house. Does the pressure just stay low like 25 PSI, or is the pump cycling on and off?

 

[JustaDIYer]

Watch the gauge while you are experiencing low pressure in the house. Does the pressure just stay low like 25 PSI, or is the pump cycling on and off?

Was steady at 25 psi, pump running constantly with sprinklers on

 

[Valveman]

And no, I don't compare house usage while sprinklers are running. The decrease is while sprinklers are not running.

25 PSI while sprinklers are running means the sprinklers are using more than the pump can supply, or you have a leak after the zone valves. What does the pressure do and how does it feel when not running the sprinklers?

 

[JustaDIYer]

Had the well guy out and he found the issue. Had a lot of debris in the elbow leading up to the switch. He's the one who installed the pump a couple years ago and said the pump is capable of 10-13gpm easily.

So, I'll swap out the fittings around the switch and see what happens.

Thanks!

 

[Reach4]

A 32-gallon tank is undersized for such a pump without a CSV. That pump would be oversized for a normal house, but maybe you like to irrigate fast.

Clogged nipple to the pressure switch can make the pressure switch action delayed. Sometimes the pressure gauge shares the nipple. You can put a garden-hose thread pressure gauge on the drain valve temporarily to help with some troubleshooting.