Pump throttling procedure

[Ethan Brush]

I have a very shallow well, maybe only 5-10 feet of head. I may need some restriction in the line to get over the recommended pump curve of 3-16 GPM I'm not quite clear on the procedure. Do I do this without the pressure tank, or with the tank connected and the pump charging it at the lower operating range of 40psi? I would think the latter. If so, how do I measure the flow? Just time filing up a bucket and find that level of restriction where I get 16 GPM while the pressure gauge hovers at 40?

 

[Reach4]

There are 15 GPM Dole valves which are designed to limit flow rate.

 

[Sponsor]

 

[Ethan Brush]

There are 15 GPM Dole valves which are designed to limit flow rate.

I am aware, but if I just use a ball valve, how is the flow rate determined?

 

[Reach4]

GPM filling a 5 gallon bucket, flow rate is 300/s , where s represents the number of seconds to fill the bucket. But that is not quite what you need.

Suppose your pressure switch is set for 40/60 psi, with the precharge set at 35 psi because you have a jet pump. I think you want to know the flow rate while filling the pressure tank when the backpressure is maybe 36 psi.

It seems to me that you could get close by looking at the drawdown on the pressure tank and how long it takes for the tank to fill to cutoff.

We know that the flow rate will be bigger at cut-on than at cut off, but I think you could pick your desired gpm at 36 psi on the pump curve and see what the gpm is at maybe 34 psi higher. A straight-line aproximation could determine an average fill rate in the middle of your range. Then use that to pick a target tank-fill rate. For drawdown, you could measure, or you could aproximate between about 25 and 30% of nominal capacity.

Also note that usually the tank does not empty of water before the pump starts delivering.

When the pump turns on for your timing test, you need to stop other water consumption.

As the cutoff pressure gets closer to the max pressure of the pump, I think this process would get less useful-- the pump curve would be much farther from linear.

Make sure that valve never gets shut.
I am not a pro.

 

[Fitter30]

Do not use a ball valve for flow control use a globe valve. Size the valve at least one size smaller than pipe size.

 

[Ethan Brush]

Ok, thanks guys.

 

[LLigetfa]

It is difficult to precisely control a full port ball valve to limit GPM and over time, there could be wear that changes the GPM. The smaller the full port opening, the easier it is to adjust.

Over a decade ago, I was developing my well and used a 1" full port ball valve to regulate the GPM output to match the well recovery rate. The process of developing the well brought up fine sediment which caused wear on the ball valve and this was over just a couple of days. Dole valves are designed to resist wear.

My water treatment system uses with a micronizer that has an adjustable bypass valve (item #5) which does wear over time. I have to replace it about every ten years.