Well recharge rate too low

[Larry Schwarcz]

I've been having issues with my residential well that we use strictly for irrigation. Some of you may have seen my other threads; Change pressure switch from 20-35 to 40-60? and To CSV or not to CSV.

I've been having issues with the pump cycling from about 36 PSI to 43 PSI, shut off and then cycle again.

I bought, but have not yet installed (was going to be today's project) a CSV from valveman but I believe my root issue is my well is not recharging fast enough.

Quick background: We bought this house 4 years ago and the well was already here. Recently the pump was not working well and started leaking. I did check out fixing the leak but in the end the leaks were from worn brass bushings and it was not worth fixing.

I now have a Hallmark 1/2 HP 115V submersible pump installed (old pump was above ground deep well 1/2 HP pump).

What I discovered today is that the pump is taking water out of the well faster than the well can recharge it!

Well data:
- 6 inch steel casing
- 35 feet deep (bottom of well)
- 20 feet down to pump water inlet
- 13 feet down to water level when pump not running

I did a quick test today to find the recharge rate:

- I tied a weight onto a nylon string and could hear the splash of water at 13 feet.
- Turned on water to make pump run (hose bibb right next to well (my flow gauge maxed out at 12 gpm). When I could hear the pump "banging" because the water level was lower than the pump inlet I unplugged the pump and timed how long it would take to refill the well to the 13 foot deep mark. This took about 4.75 minutes. If I did my calculations correctly this is a recharge rate of about 2.2 GPM.

It seems to me that if I pull more than 2.2 GPM then I'll pump the well level to below the pump inlet and have issues.

I was never aware of an issue like this with the old pump and the prior house owner told me that the well had never run dry on him. To be fair, it's not running dry, just not recharging fast enough.

Where I live, Hillsboro, OR, we are not in a drought situation.

It seems to me that the only real solution is to do something to increase the recharge rate. Extending the well pipe will only delay the issue. If I'm pulling more water than the well can produce in any time period, I guess the only solution is to fix the well to recharge faster (if possible).

Any suggestions or ideas?

Thanks in advance!
Larry.

 

[Reach4]

One possibility is to add a device to detect when you run out of water, and shut down the pump for some number of minutes.

Another possibility is to lower the pump another 5 or 7 ft.

Another possibility is to use a lower-flow emitter. Try 4 gpm, and see how long it takes to run dry. I am thinking that the fill rate may be higher when the water level is lower. So refilling the first two feet may be significantly faster than refilling the last two feet.

 

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[Bannerman]

I've been having issues with the pump cycling from about 36 PSI to 43 PSI, shut off and then cycle again.

At first glance, this appears to indicate the pump is capable of supplying water at a higher flow rate than the flow rate water is being consumed at, with the cycling further worsened by a pressure switch that has the cutout pressure adjusted to 43 psi and the differential pressure adjusted lower than the standard 20 psi.

What pressure range is your Pressure Switch currently adjusted to?

In yet another thread posted today, you included a chart which specified the Hallmark pump has a maximum 150' head capacity. In this thread, you stated your well's static water level is 13', and so if the water level is being pulled down a further 7' to 20' (just above the pump's inlet screen), then the maximum pressure that pump will be capable of building will be 56.2 psi (150' - 20' = 130' / 2.31 feet per psi).

The appropriate pressure switch range for that Hallmark pump should then be 30/50 psi, which will permit the pump to work within the pressure range it is capable of building at the depth it is currently placed at. The difference between 56.2 and a 50 psi pressure switch cutout pressure, will ensure the pump will reliably build to 50 psi regardless of the water level within the well. If the pump is further lowered an additional 5' - 7' within the well, then the pressure switch range may need to be further lowered somewhat to maintain at least a 5 psi recommended differential between the pump's maximum pressure capability at that depth, vs the actual working cut-out pressure.

 

[Bannerman]

When I could hear the pump "banging" because the water level was lower than the pump inlet I unplugged the pump

Did the pump actually stop supplying water, or are you only assuming the water level was drawn down lower than the pump's inlet screen?

If the water level had been drawn down to the pump's inlet screen, then the pump will have been drawing air.

Turned on water to make pump run (hose bibb right next to well (my flow gauge maxed out at 12 gpm).

As your pump is capable of supplying 12 gpm, even if the water is being consumed at a lower rate, the pump will continue pumping at 12 gpm, so the excess flow above the rate of consumption, will flow into the pressure tank until the pressure rises to the pressure switch cut-out pressure, which will then cause the pump to shut off. Further water consumption will then cause the system pressure to again lower, and the pump will be reactivated once the pressure becomes reduced to the pressure switch cut-in pressure, and so that cycling will continue to occur for the entire time water continues to be consumed.

The CSV will typically reduce the flow rate drawn from the well as once the pump is activated, the CSV will reduce the flow rate delivered from the pump, so the pump supply rate will equal the rate of water consumption.

For example, if your irrigation system consumes 4 gpm, then the pump will continue to deliver 4 gpm from the well, for the entire time water continues to be consumed. Once no water is further needed, the CSV will permit only 1 gpm to pass, which will cause the pressure tank to continue to fill until the pressure switch cut-out pressure is achieved, which will cause the PS to shut off the pump.

Water flow into a well (recovery rate), will typically be greater when the water level is pulled down to a low level vs when the water level is high, close to the static level.

 

[Valveman]

With the CSV you should be able to use less water than the well is making without the pump cycling on and off. In this way you can match the flow used to the amount the well can produce without cycling the pump. If the well is being pumped dry, the sprinkler pressure should fall to zero when the pump shuts off.