I'm confused. I just ran out of water.

It's dry season, and it's a new house (to me) and the water tanks are
'empty' and the wells are barely re-filling them.

I ran some calculations which, if I may, I would like to compare with your
situation.

Fundamentally, I ask: Is 3,094 US gallons a reasonable storage level?

Demographics:
- Family of five (two teens)
- 35,000 gallon open-air pool (takes about 500 gallons of water every few
days to refill due to plumbing leaks and surface evaporation)
- 20 irrigation zones, each of which has about 10 rain-man 1800 sprinklers
- Watering schedule was set to every other day, 20 minutes per zone
- The well pump runs for a few minutes (varies from a minute to about ten
minutes) and then shuts off due to lack of water ... waits a prescribed 30
minutes ... and then starts the cycle anew). I'm guessing roughly 100
gallons per cycle (but that's a very rough guess as there is no meter).
- Northern California (zero rain from about March to about December, but,
when it rains (January/February/March), it pours!)

Calculations:
- I have two equal-sized cylindrical steel water tanks
- I have only one well (which is 500 feet deep)
- There is no meter anywhere on the water flow (hence my dilemma).
- I measured the two steel water tanks at 120" inches tall & 241.5 inches
in circumference (the diameter is difficult to measure as the top is
domed).
- Geometry gives us, however, a diameter of 77 inches per tank.
- Geometry gives us a volume of 556,936.45 cubic inches per tank.
- This web site converts cubic inches to US wet gallons:
http://www.onlineconversion.com/volume.htm
- Using that web site, the nominal capacity of each tank calculates to
2,411 gallons (i.e., 1 US gallon is 231 cubic inches)
- That means, the total nominal volume for both tanks is twice that, i.e.,
4,822 gallons.
- However, the usable volume is aparently only 3,094 gallons (1,547 gallons
per tank).
- The fire hydrant seems to get 1,446 gallons (723 gallons per tank)
- And the top air space of 282 gallons is apparently unused (141 gallons
per tank)
- Doublechecking the math:
- 1,446 fire gallons + 3,094 house gallons + 282 air space gallons = 4,822
nominal gallons.

Fundamentally, I ask:
Q: Is 3,094 gallons a reasonable usable quantity for a family of four?


PLEASE IGNORE IF NOT INTERESTED THE FURTHER CALCULATION DETAILS BELOW:
- Based on float movement, the total 'range' of usable water is only 77
linear inches (which calculates to 357,367.55 cubic inches, or 1,547
gallons per tank, which is a total usable water of 3,094 gallons).
- This number comes from 36in + 77in + 7in = 120 inches as explained below:
a) The level indicator is a wooden block which goes down when the water
level goes up, and which goes up when the water level goes down (i.e.,
reverse logic).
b) The level indicator block never makes it closer than 36 inches to the
top of the tank, which, (by the reverse logic of the float mechanism) means
that the bottom 36 inches of water is for the mandatory fire hydrant on the
property (which calculates to 167,081 cubic inches per tank, or 723 gallons
per tank, for a total fire-only storage of 1,446 gallons).
c) The level indicator block never makes it closer than 7 inches to the
bottom of the tank, which (again, by the reverse logic of the float
mechanism) means that the top 7 inches of the tank is never reached (which
calculates to 32,488 cubic inches of air at the top, or 141 gallons per
tank).
- To put it together, 7 inches of air space + 77 inches of usable water +
36 inches for the fire hydrant = 120 inches of nominal tank height.
- In gallons, that works out to 282 air space gallons + 3,094 house gallons
+ 1,446 fire gallons = 4,822 nominal gallons.

I know it's a lot of calculations ... but ... fundamentally ... I ask if
this setup seems weird to you?

To me, it seems like not enough water (and the fact I ran out today shows
that ... but maybe I've been irrigating too much and I 'should' fix the
pool leaks also ... plus maybe this is a lull in the water supply since it
doesn't rain for 9 or 10 months of the year out here in the hills.

Do any of you have comparison figures?