Hillview Circle, Dripping Springs, TX 78620
Hillview Addition, Section 1, Lot 12 (10.67
acres), Hays County
Start Date: approximately 10/15/96
Date: approximately 3/3/99
dimensions: 40' x 80' x 14'
collection area: 3240 sq. ft.
storage capacity: Design - 20,000 gallons, Useable - approx. 19,300 gallons
Potable and non-potable via diverter valve before filtration and disinfection
method: Pumped with gravity assistance to some areas
method: Ultraviolet light incl. 20-micron and 5-micron sediment and 3-micron
activated charcoal pre-filters
In the summer of
1996 I attended a seminar on rainwater harvesting at the Lady Bird Johnson Wildflower Research Center in Austin. Two
years earlier, we experienced a spring drought and a low water level in our
250-ft deep well. Combine that scare with the poor well water quality due to
extreme hardness and sulfuric odor, and you see why we were looking for
alternatives. After also researching other rainwater harvesting sources and
case histories, we determined that this was the alternative of choice over
drilling an 800-900 ft deep well to sweeter water. Furthermore, we did not want
to use questionable carcinogenic chemical treatments and didn't want to deal
with large filters and water softeners, which consume and discharge huge
amounts of salts. So, after completing construction of the collection surface,
the water barn, we were ready to begin capturing the Texas hill
country's 32-33 inch annual rainfall. Our 3200 square foot roof can potentially
capture an average 61,440 gallons per year. This averages to about 168
available gallons per day. With our low flow and low flush fixtures and
toilets, this is ample supply for the three adults currently residing on the
I used 4" schedule 40 PVC pipe and fittings for
the raw delivery system. Metal strapping and cable support the piping. I used a
1/8" per foot slope in the tubing from the downspout pipes to the tank.
I first designed
a gutter system based on the seminar suggestions using six-inch thin wall (SDR)
PVC tubing. A 1½ inch wide section of the entire length of gutter including the
fittings is removed to accept the ends of the 2½ to 3 inch roofing overhang.
This system results in an essentially closed gutter and perhaps prevents entry
of very large debris objects. However, it is also difficult to clean, if
necessary, and it makes a nice place for bugs, wasps, and even birds to hide
and nest. So, when it was time to install, I elected to use conventional 5-inch
continuous aluminum extruded gutters.
the first-flush vertical wash pipe system could be installed. The
principal of this type of system is based on the fact that the first 10 or so
gallons of rainwater washed from the roof surface contains most of the dirt and
contaminants that have settled onto the roof and gutters.
Those ten gallons of
dirty rainwater are diverted to the vertical tubing and then the additional
water that is collected in the gutters flows directly into the tank. I have made improvements in this age-old
system so that the system works automatically. These improvements have shown very positive results in continuous and
gauge measures the level of water inside the tank and displays it in inches. In
my 20,000 gallon tank, each 8.5 inches equals about 1000 gallons. Here the gage
shows 90 inches, so, 1000 x 90/8.5 = 10,588 gallons.
system draws raw rainwater from the tank and then sends soft, pure, clean
drinking water to the house. A 1/2 horsepower shallow-well pump draws the water
from the tank and pressurizes
it to 30 - 40 psig. A 40-gallon air-charged pressure tank and regulator allows
water usage without running the pump until pressure reduces to 30 psig.
There are two particulate filters in series, rated at 5 and 3-micron particle
size, and a disinfecting ultraviolet light rated at 10 gallons per minute
flow. The 40-watt light is rated at 9600 hours, or about 13 months of
There is also a
floating filter inside the storage tank. Water is drawn from a port at the
bottom of the tank, but a flexible hose is attached to the port on the inside
of the tank and connects to a large filter that is suspended by float about 20
inches below the water surface. The cleanest water is always off both the
surface and the bottom of the tank. There are also two minor but necessary
components; a back flow valve and a manual valve between the tank and the
pump. A supply valve is provided to switch back to the water well during
rainwater system down times.
Barn Truss Construction Plan
Barn Construction Plan
Barn Elevation Plan
Major Equipment Detail
Galvalume, 7/8” high-ridge Cee-panel
Fiberglass water tank:
Manufacturer: Permian Tank
Ultraviolet water purifier:
Atlantic Ultraviolet Corp.
name / Model: Mighty Pure / MP36B
Flow: 12 gpm
Water pump w/82 gal equivalent pre-charged tank: