On Sat, 12 Sep 2015 15:08:16 -0700, Don Y
wrote:

On 9/12/2015 2:59 PM, wrote:
As long as the tank is full, not much danger of it collapsing under
any "reasonable" load. When less than full, obviously it would
support less weight.

Rains (which is where the water to fill the tank originates) come twice
a year, here. A month in Summer (technically, "Monsoon") and a month
or so in Winter. We can, theoretically, capture about 20,000G in a
year -- almost evenly split between the two rainy seasons.

But, storing 10K gallons would be a huge undertaking. And, considerably
more expensive. "Incentives" make a 2000G (plastic) tank virtually "free"
if you do the labor yourself (dig hole, plumb irrigation, etc.). Delivery
and setup charges for concrete tank would easily make this a silly
undertaking.

[Water isn't THAT expensive. OTOH, the sewer charges on the water
delivered to your house BUT NEVER PROCESSED THROUGH THE SANITARY SEWER
and taxes make a "virtually free" undertaking reasonable!]

My brother delivered and installed precast concrete septic tanks and
cisterns for over 10 years - quite a few over 2000 gallons.

A bit more involved than hauling a plastic one home in your pickup and
kicking it into a hole - - -

Exactly. No do-overs. It turns into a PAID project instead of a
weekend warrior ordeal.
Around here water is getting quite expensive, and then we have a
stormwater run-off fee as well. The more trees you have (and the
bigger) the more discount you get on that - and even rain barrells
give you a discount.

Counting both, it might not take too long to pay for even a concrete
cistern installation (some new homes are getting them as "standard
equipment" the last couple of years. A bonus is you can actually water
the lawn in the dry season (forbidden here all summer) so the cost of
keeping a decent looking lawn would go way down too.

Remember plastic doesn't last forever - you could end up with a small
sink-hole in 20 years or so - - -