# Pump calculator.. Anyone Willing To Explain?

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#### TVL

##### Member
I know electrical very well and I know a "little" about plumbing and my well system, but I would like to know more. I have seen where an individual on this site has utilized the "pump calculator" at the following site:

https://pentairaes.com/pump-calculator

My well system seems to function perfectly, but it would be "cool" to determine what the pump calculator will tell me about my system. Possibly my system is right where it should be or possibly I will learn something valuable???

1- For the "YOUR SPECIFICATIONS" section, I understand what value needs to be populated in each block with the exception of the <Total Pumping Lift> and the <Misc. Head Loss> I'm assuming total pumping lift is the actual distance from the pump inlet to the TOP of the well and I have no idea what misc. head loss entails.

2- Then, if someone also had time to explain what the entire "SUMMARY" section tells me, I would be very appreciative ………………… especially the value derived for <Total Pump Head Required> and <PSI>

I appreciate any help or knowledge someone may be willing to share!

#### Valveman

##### Cary Austin
Staff member
Yeah that calculator is pretty confusing. Pumping lift will be depth to water in the well. Mis Head Loss will be the pressure you need in the house converted to feet of head. (2.31' = 1 PSI) So 50 PSI is 115' of head. Total pump head required is given in feet of head and PSI.

So if your flow rate required is 10 GPM and the Total Pump Head required is 172', then you need a pump that can produce 10 GPM from 172'.

#### TVL

##### Member
Thanks Valveman!

So, our water well is for irrigation purposes only. We have a 151 foot deep 4" well with the static water level at 111 feet. The pump hangs at approximately 126 feet. We are using a F&W pump: model 4F10S10301

With the pump calculator fields properly populated, I received the following summary. If I were analyzing the performance or whatever, does this summary tell me anything at all?

PS: if the following summary is primarily utilized to help choose the proper size pump to meet one's needs, then how does the info relate to me and my setup. The irrigation system is designed so that none of the 14 zones will ever cycle. Each zone is designed to use approximately 11 GPM. I am simply curious as to how the summary relates to my setup. Possibly, I have the perfect setup, then again, maybe the summary indicates I need a different size pump ...……. which I will certainly consider when the time comes. I'm assuming the Total Pump Head Required & PSI are of extreme importance when choosing a pump. I don't even know if my pumps meets these requirements??????

Last edited:

Staff member

#### TVL

##### Member
All you are really doing is figuring your Total Dynamic Head or TDH, which is 258.7 feet.

Thanks Valveman!

So, if I understand correctly, by populating the "Your Specifications" section, the pump calculator then yields a value that is comparable to a pump that would hang at that particular depth (258.7 ft in my situation) with no other piping or restrictions involved. Now, an individual can better determine what to expect the GPM rate to be which then allows them to more precisely pick the correct pump for their application. If I'm understanding correctly, then this is great information.

And last, what does the 112.1 PSI value indicate?

Thanks again!

#### Reach4

##### Well-Known Member
And last, what does the 112.1 PSI value indicate?
That would be the 258.7 ft converted to PSI.

On a different topic, what pressure does your sprinkler head open pipe into a ditch, or the line driving your drip system require? Valveman selected 50 PSI as a number, but you should compare that to the needs of your intended distribution system.

#### Valveman

##### Cary Austin
Staff member
Yeah I just picked 50 PSI (115') because it is the most common house pressure. But if you have a two story house I would recommend 60 PSI (138'), or if you have a house up on a 100' tall hill I recommend 90 PSI (207'). See how PSI needed can be converted into feet of head, which is what the pump sees? 2.31' = 1PSI or 231' = 100 PSI and so on.....

#### TVL

##### Member
That would be the 258.7 ft converted to PSI.

On a different topic, what pressure does your sprinkler head open pipe into a ditch, or the line driving your drip system require? Valveman selected 50 PSI as a number, but you should compare that to the needs of your intended distribution system.

That would be the 258.7 ft converted to PSI. So, is that the same as back pressure?? Is too much back pressure bad?

On a different topic, what pressure does your sprinkler head open pipe into a ditch, or the line driving your drip system require? I'm not exactly sure what you are asking. The drip system zone has a 25 PSI regulator on it. All of the other irrigation zones run anywhere between 48 and 58 PSI. That is the measurement taken by the gauge located at the pressure tank/pressure switch. The pressure gauge reading after going through the Lakos sand separator and Vu-Flo filter measures anywhere from 40 to 50 PSI. My pressure switch is set at 43/63 PSI

#### Valveman

##### Cary Austin
Staff member
A pump can take a lot of back pressure without hurting it, but 1-2 PSI too much will deadhead (block off all flow) and burn up the pump. Until that critical point, which you just don't want to go to, increasing backpressure actually decreases the load on the pump and makes its work easier. Not enough back pressure can be just as bad as deadheading a pump. That is why you do the calculations and pick the right pump as 258.7 feet of head is perfect for a 3/4HP, 10 GPM pump. But 258' would deadhead and burn up a 1/2HP, 10 GPM pump and not be enough back pressure for a 3HP, 10 GPM pump. Pumps have a pretty large sweet spot, but you got to stay inside it.

#### TVL

##### Member

Thanks Valveman for the information and the willingness to share it!

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Hey, wait a minute.

This is awkward, but...

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