On 15 Nov 2005 07:57:33 -0800, "
wrote:

I'm having a well put in in the foothills just east of the Sierran
Nevada mountains. The area is rocky (decomposed granite) and other
homeowners in the area have wells ranging from 150 to about 300 feet
with good flow rates. One neighbor just put in a well (same driller)
and gets 20 gal/minute. My well digger went down to 390 feet without
finding any significant water, but he thought there might be some
higher up based on the hole filling overnight. So he removed the "mud"
from the hole but found only about 7 gal/minute (which seems inadequate
for a 3700 sq ft house). He says the only other (than 7 gal/minute)
option at this point would be to go deeper. This would be deeper than
any of my neighbors, most of whom are at slightly higher elevations
than me.

My questions:

1) Would it make sense to drill elsewhere on my 2 acre lot? It seems
like perhaps the water table varies since my neighbors have good wells.
Starting over is an expensive proposition but may be the only option if
water isn't found deeper.

2) What other choices are there if more water is not found in the
present hole. Can large storage tanks be used to "buffer" the
inadequate flow?

3) What is a minimum reasonable flow rate? We'd hoped to use a new
variable speed pump that can handle up to 30 gal/minute.

Serious advice is welcome.

Just went through a similar situation.

I'm in OH. The well driller told me these guidelines:

20 gpm is good for unrestricted use for 4 or more people in a large
house on a large lot (2+ acres of lawn). Unrestricted use includes
frequent lawn watering, garden irregation, laundry, washing cars, etc.

10 gpm is good for all of the above with some restrictions. Not
trying to wash the car while doing laundry and the lawn sprinklers are
on, for example.

5 gpm: will be ok to water the garden and shrubs; forget about
frequent lawn watering, such as a sprinkler system, unless it's a very
small lot.

Below 5: Aux. storage recommended, from 300 to 1000 or more gallons
down at the 2-3 gpm level.

Having said that, he then said that if you are willing to forgo any
significant irrigation of lawn or garden, and you don't mind being
careful to sequence things, such as spreading laundry over several
days, you can manage on a few gpm.

The numbers may sound high to some, but flows do tend to decrease a
bit over time and vary seasonally, and can also be greatly affected by
load on the acquifer from more building in the area.

The problem with low flows and no aux storage (he told me) is that if
you aren't careful, and you keep drawing the well down a lot, or
worse, running it dry, the water washing up and down the sides of the
well tends to loosen sand and grit, which gunks up the water supply
and leads to early pump failure.

FWIW, in our case, we drilled two wells, neither went above 2 gpm
although there were some 20 gpm wells within a thousand yards or so.

We walked away from the deal (it was contingent on getting a good
well).


HTH,

Paul