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Well performance calculators

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The arithmetic is the easy part.

Specific capacity is a division. Wire-to-water efficiency is two multiplications. Anybody can put those on a web page and plenty of people have. What almost nobody tells you is the handful of things that quietly make the answers wrong — and those are the reason a district’s numbers drift for years before anyone notices.

These three do. They run on the same published hydraulics engine that produces our well condition reports, so they cannot quietly disagree with it.

Calculator 01

Specific capacity

How many gallons a minute this well gives up for each foot you pull it down. The single best early indicator of screen fouling — and the number most often compared wrongly.

gpm
ft below grade, pump off and recovered
ft below grade, at the rate above
gpm — we will tell you whether the comparison is valid
only changes the transmissivity rule of thumb
Specific capacity —
Drawdown—
Transmissivity — order of magnitude only—

Calculator 02

Wire-to-water efficiency

What fraction of the electricity you buy actually leaves the wellhead as water. Everything else is heat, and you are paying for all of it.

gpm
ft below grade — this is the lift, and it is half the head
psi at the wellhead gauge
kW measured at the panel, not nameplate horsepower
acre-feet per year
$ per kWh
Wire-to-water efficiency—
Total dynamic head — built, not typed—
Water horsepower—
Power going in—
Energy intensity—
Annual energy cost—

Calculator 03

Slowing a well pump down

The affinity laws, and the two things they leave out: what a well actually saves, and the speed below which the pump stops delivering anything at all.

gpm
ft
kW at the panel
rpm at full speed — the nameplate figure the three readings above were taken at
rpm. Raise it and flow, head and power rise; lower it and they fall.
ft — the pumping water level. This is what the cube law ignores.
ft at zero flow, off the pump curve
Power at that speed — this well—
What the cube law alone would predict—
Speed—
Flow at that speed—
Head at that speed—
Below this speed the pump delivers nothing—
The same, on a 60 Hz drive—

One well, once, is a spot check. Every number on this page is worth far more as a trend than as a reading: specific capacity falling at a steady rate is screen fouling, wire-to-water falling while specific capacity holds is pump wear, and both falling together is usually the aquifer. Telling those three apart takes a record, not a calculator — which is what the platform is for.