Tapping water from well by gravity -- calculations

[FactChecker]

If sustained flow is less than 5000 litres per hour, the well is classed as a dry hole, and so costs less.

That sounds wrong. That is 22 gallons per minute. Are you sure it is not 5000 liters per day? That would be 0.9 gallons per day, which seems reasonable to call it dry.

 

[Baluncore]

That sounds wrong. That is 22 gallons per minute.

I use SI litres or m³, as it is too easy to confuse gal(imp) with gal(US).

The critical estimated flow was 1000 gal(imp) per hour, but is now 5000 litre/hr.
That is a small farm supply, not a house supply.
It is not worth running a well pump for less.

Farmers are economists, who use land, to convert water into money.
When it is dry, they need more water to stay afloat financially.

 

[Averagesupernova]

Farmers are economists, who use land, to convert water into money.
When it is dry, they need more water to stay afloat financially.

To put things into perspective, an inch of rain on one acre is about 27000 gallons. The size of the well used for irrigation of crops is in an entirely different league than a piddly 1000 gallon per hour well. In the USA a 1000 gallon per hour well will keep up with spraying crops but certainly not irrigation.
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1000 gallons per hour won't meet the demands of large dairy operations either. More than one well is needed if for no other reason than backup. Even in communities with public water systems where the reliability is very good they will have a well or two.

 

[FactChecker]

I use SI litres or m³, as it is too easy to confuse gal(imp) with gal(US).

Good point. My recent experience was in terms of US gallons. I see why liters is better.

The critical estimated flow was 1000 gal(imp) per hour, but is now 5000 litre/hr.
That is a small farm supply, not a house supply.
It is not worth running a well pump for less.

Farmers are economists, who use land, to convert water into money.
When it is dry, they need more water to stay afloat financially.

You are talking about a working farm. I have only been considering a small, non-working farm that people live on with a hand-full of animals. I have no idea how much water a working farm of any size requires.

 

[Baluncore]

If sustained flow is less than 5000 litres per hour, the well is classed as a dry hole, and so costs less.

As I explained, 5000 litres per hour is classed as a dry well.

 

[FactChecker]

As I explained, 5000 litres per hour is classed as a dry well.

In the US the term "dry well" means something completely different. They are for putting rainwater into the ground.
A residential well with a recovery rate of 5000 liters per hour (22 USG/m) would be considered excellent. This is from https://waterdefense.org/:

In general, well recovery rates measured for 24-hours can run from a fraction of a gallon each minute—a poor flow rate—to 3 gallons per minute, which is serviceable but not great.​

​

Good recovery rates can run from 5 gallons a minute—an acceptable number comparable to residential use—to over 10 gallons per minute which is an excellent recovery rate for residential areas.​

 

[Juanda]

I use SI litres or m³, as it is too easy to confuse gal(imp) with gal(US).

When I thought imperial units could not get any more confusing I just learned that imperial and US gallons are not the same. I'll keep that in mind.

It reminds me of when I learned UK threads and US threads are not the same even if they may have the same size and pitch because the fundamental triangle of the teeth has a different angle. Just saying it in case another EU poor soul has to deal with it and avoid the mistakes I have already committed.

 

[jack action]

I just learned that imperial and US gallons are not the same.

Actually, they have the same "definition": 4 quarts; and 1 quart is 2 pints; and 1 pint is 2 cups; and 1 cup is 2 teacups. The big difference is that an imperial teacup is 5 fluid ounces and the US teacup is 4 fluid ounces.

And, of course, there is a small 4% difference between the imperial and US fluid ounces. That is because the official modern basic volume definitions have been established to be the gallon, which are:

The Weights and Measures Act 1963 refined this definition [the imperial gallon] to be the volume of 10 pounds of distilled water of density 0.998859 g/mL weighed in air of density 0.001217 g/mL against weights of density 8.136 g/mL, which works out to 4.546092 L. The Weights and Measures Act 1985 defined a gallon to be exactly 4.54609 L (approximately 277.4194 cu in).

The US liquid gallon (frequently called simply "gallon") is legally defined as 231 cubic inches, which is exactly 3.785411784 litres.

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The most fascinating definition for me was the inch, which in several languages is called a "thumb". Younger - I speak French, for which it is the case - I couldn't figure out how one could have such a short thumb. How did they arrive at such a definition for a "thumb"?

It turns out that the definition of a thumb is the difference between one hand and one palm; so it is the width of the thumb, not its length:

In many other European languages, the word for "inch" is the same as or derived from the word for "thumb", as a man's thumb is about an inch wide (and this was even sometimes used to define the inch).

1. shaftment (with thumb open)​

2. hand (= 1 palm + 1 thumb = 4 inches [or "thumbs"])​

3. palm (= 4 fingers = 3 inches [or "thumbs"])​

4. span​

5-6. finger/digit (= 3/4 inch)​

(source)​

I can just imagine some ancient conversations where one guy asks the other: "How tall is this horse?", "17 hands", the other replied. "No way! Show me." And then the other guy just measuring with one hand over the other, excluding the thumb. "That is not a hand, it's a palm, you idiot! A hand must include the thumb!"