Sprinkler pressure low....please help

[Kelly carlson]

Hi all, hoping to find some sort of guidance. My sprinkler system is a four old underground rain bird system that covers 17000 sq ft with 8 zones. When I turn a zone on the pressure and flow are great. A couple minutes into the cycle the zone will lose some pressure and have a bad flow. This will continue until there is barely a flow. If I turn it off and start another cycle the same thing happens. Great pressure for a few minutes, and then it loses it. I am on well water with a constant pressure system. I just had my pump dug up and replaced as I thought that was the issue but apparently it wasn’t. C0uld it be a leak in the stations? We do have our lawn aerated. Could that have down something? Any guidance is appreciated!

 

[Valveman]

What kind of "constant pressure" system do you have?

 

[Sponsor]

 

[Kelly carlson]

What kind of "constant pressure" system do you have?

It's a Flow-Thru FT266

 

[Reach4]

Sounds like the well or pump or piping before the pressure tank cannot keep up. Not even close.
I think that model number you gave is for an 86 gallon pressure tank. https://www.flexconind.com/products/specialty-products/flow-thru-/

What you might be able to do is to program your controller to shut off for a few minutes. Ideally the controller would turn the sprinklers as the pressure approached cutoff.

What do you know about your pump and your well?

Is there by chance a filter before the pressure tank? That would not be normal, but it could explain things maybe.

If I turn it off and start another cycle the same thing happens.

I presume there is a significant time between you turning off the first zone, and the next zone starting. If not, that would change my thoughts.

 

[Kelly carlson]

Sounds like the well or pump or piping before the pressure tank cannot keep up. Not even close.
I think that model number you gave is for an 86 gallon pressure tank. https://www.flexconind.com/products/specialty-products/flow-thru-/

What you might be able to do is to program your controller to shut off for a few minutes. Ideally the controller would turn the sprinklers as the pressure approached cutoff.

What do you know about your pump and your well?

Is there by chance a filter before the pressure tank? That would not be normal, but it could explain things maybe.

I presume there is a significant time between you turning off the first zone, and the next zone starting. If not, that would change my thoughts.

 

[Kelly carlson]

Yes the pump guy told me that our sprinkler system is too big to keep up with the pump/well. We are going to try and change out the nozzles on our sprinkler heads to see if that helps. My confusion is that it worked fine for 3 years.

No filter before the pressure tank

 

[Reach4]

It may be that the well is getting clogged and could be rejuvenated.
It may be that the aquifer water level has dropped.
It may be that the pump is failing.

Are you looking for some DIY testing ideas? Mine would be to turn off the pump, and open one or more silcocks. After the water pressure drops to zero, turn on the pump.

If the water pressure does not rise enough to reach the pump cut-on pressure, measure the flow rate rate through the silcock(s). With a 5 gallon bucket, if S is the number of seconds to fill the bucket, GPM=300/S.

If the water pressure does rise enough to reach the pump cut-on pressure, you can temporarily raise the air precharge higher than the cut-off pressure. That keeps the pressure tank from accepting water.

What you will know is what your well+pump can deliver. If that is close to your pump expectation, modify your irrigation to work with the available steady-state water.