Q&A about the definition of well water static head.

This articl eseries defines the static head in a well and we explain how the well's static head can compensate for a well with a poor flow rate.

Static Head FAQs - Well Water Starting Quantity

These questions and answers about the size, importance, and volume of the column of water inside of a water well - the well's static head - were posted originally at WELL DYNAMIC HEAD & STATIC HEAD DEFINITION - please be sure to check out that page.

On 2018-08-14 by (mod) - Is there a standard depth for the air gap?

No. Every well and water supply system is going to be a bit different.

In fact even within one specific water well the height or top of the static head varies seasonally as the level of the supplying water table varies too.

On 2018-08-13 by Well Air Gap

@Well Air Gap,
Is there a standard depth for the air gap?

Is there a standard in the well drilling business on the air gap in the casing?

On 2018-05-07 by (mod) - consider lift height when sizing a well pump

It's not just the "GPM" rating of the pump you need to consider. Take a look at the manufacturer's table of pump capacity of the new pump and you should find numbers giving the reduction in flow rate as a function of lift height - for that specific pump.

Details and typical pump capacity charts are

at WATER PUMP CAPACITIES TYPES RATES GPM

There you'll see that a pump nominally rated at 5 GPM is probably so-rated with nearly a zero lift. If your pump is rated that way, having to lift water 115 ft is going to mean that pump is barely going to get water out of the well.

Conversely and in a table near the end of that article you'll see the information you need.

On 2018-05-07 by Mark C

I am replacing a. Franklin /Fairbanks motor pump .1/2 hp 230 v3wire. I want to install a 2 wire ,1/2 hp 240 v in its place.

The drop pipe is 115 ft. My pressure tank looks to be about 40 gal.,pressure as. Is set 20/40

I don't know the gpm of the pump.House is small cottage,1bath sink ,shower,toilet 1 kitchen sink , Would a 5 gom be okay?

On 2017-08-06 7 by (mod) - the volume of a cylinder Vcyl = pi x r2 x h

Special thanks to readers Valerie, Anonymous, and Steven

Before your critique our table in WELL DYNAMIC HEAD & STATIC HEAD DEFINITION showed a grossly-wrong 0.7L per M of 15cm diameter well bore.

using the formula for the volume of a cylinder Vcyl = pi x r2 x h

that is 15cm in diameter (or 7.5cm radius) and 1 meter in height:

radius r = 1/2 the diameter or 7.5 cm

Vcyl = pi x r2 x h

Vcyl = pi x (7.5)2 x (100)

Vcyl = 3.1416 x 56.25 x 100 = 17,671 cm3 or

17.671 L - that should have been the correct entry in our table

Thank you Valerie, Anonymous, and Steven for pointing out my calculation mistakes.

I have corrected the article and I include your original remarkshere in the article's FAQs..

You may need to clear your browser cache to see the updated article.

On 2017-08-06 by Anonymous

how did you calculate the metric version?from where you get 0.7 lt?

On 2017-08-05 by Valerie - get the right formula and math for calculating the volume of water in a well static head

In your Table of Volume of Water in a Well your calculations of volume in metric are definitely wrong compared to gallons-feet. First, litres are smaller than gallons. The corollary of this is that there is more than one litre in a gallon. Likewise there are several feet in a meter.

Accordingly, when you multiply two larger numbers together, your product must be a larger number rather than a smaller number. So depending on whether you are calculating gallons as either Imperial (160 oz/gallon) or American (128 oz/gallon) the equivalent of 1 gallon will be either 3.78541 litres based on US gallon or 4.54 litres per Imperial Gallon.

And given a metre is 3.28084 feet that means the capacity of a 6 inch pipe (which is equivalent to a 15cm pipe) would be either 18.63 or 22.34 litres per meter based on the following formulae respectively (3.785 litres x 3.28084 ft/metre x 1.5 US gals per foot) (4.54 litres x 3.28084 ft/metre x 1.5 US gals per metre).

Both of these figures are a far cry from the .7 litres/metre you have calculated. So the only question remaining is whether you are using American or Imperial gallon measurements.

On 2016-10-17 by Steven

Your math is incorrect in your sample calculations for water volumes in a cylinder. It's the radius squared, not the diameter squared. Radius = Diameter/2.

...

Continue reading at WELL DYNAMIC HEAD & STATIC HEAD DEFINITION or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• WELL CASING DIAMETER CHOICE
• WELL FLOW RATE
  • WELL DYNAMIC HEAD & STATIC HEAD DEFINITION
  • TOTAL DYNAMIC HEAD
  • WELL YIELD, SAFE LIMITS
  • WELL YIELD DEFINITION
  • WELL YIELD IMPROVEMENT
• WELL FLOW TEST for WATER QUANTITY

Suggested citation for this web page

WELL DYNAMIC HEAD & STATIC HEAD DEFINITION FAQs at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to WATER SUPPLY, PUMPS TANKS WELLS

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