In late March, as we neared completion of construction on their new home, the sisters –Candy and Sue (see
related story) — began to fret just a bit. “There’s been no rain. Should we go ahead and buy some water for the tank?”
Wayne shook his head. “Wait,” he told them. “Let’s see what happens. April showers, right?”
We broke ground in October. It took just a little over six months to
build their home. The 30,000 gallon rainwater tank was one of the first
things to be installed, and we had a truck deliver about 2,000 gallons
of water for use during construction. The metal roof went on in
December. (If you’re collecting rainwater, you want a metal roof.)
Gutters and pipes were installed in January, and they were connected and
ready for rain in February. And then it didn’t rain. And it didn’t
rain. Remember?
And
then came April, woohoo. A couple of good storms the first two weeks of
April dumped up to four inches of rain in the area. Now, we didn’t have
a rain gauge to the measure the specific rainfall at Candy and Sue’s
house. But take a look at the photo and see what happened. I snapped
this photo in mid-April. The red bobber indicates the tank’s water
level. Almost half full, right? How is that possible, with just 4” or so
of rain?
Well, get out a pencil, and let’s do the math.
The sisters’ house has 3,532 square feet of air conditioned space.
Add the garage, front porch, the lovely screened porch at the back of
the house, and two-foot eaves on all sides, and you’ve got 5,661 square
feet of total house coverage. The roof surface is a whopping 6,289
square feet.
Got all that? Now here’s the magic: One inch of rain on 1,000 square
feet yields about 600 gallons of water. Every time it rains one inch,
the sisters harvest 3,773.4 gallons of water, or about 12% of the tank’s
capacity. Those 4 inches of rain during the first two weeks of April
produced about 15,093 gallons of water. The tank is half full.
If you’ve lived long enough in central Texas, you’ve figured out by
now that our rain often comes in big bucketfuls all at once. Yes, we’ve
got water problems in Texas, but the answer falls from the sky. We’re
all drinking rainwater; it’s just that some people choose to catch and
store it locally instead of waiting for it to flow into rivers, lakes,
and aquifers, where it’s stored and later pumped miles and miles (at
great cost) to reach homes and businesses.
The sisters decided to invest in a 30,000 gallon tank rather than a
20,000 gallon tank in order to have extra storage capacity to capture as
much rainfall as possible during the “rainy” periods of the year. Chris
Maxwell-Gaines of
Innovative Water Solutions,
who designed and installed the system, calculates that a “20,000-gallon
tank would be sufficient to supply a 4-person household. Their system
should allow them ample water supply even during drought years.”
Of course, the way the home operates and the behavior of its
inhabitants have a lot to do with water use. Naturally, the sisters’
home was designed, built, and furnished to conserve water — the way the
plumbing runs were laid out, the water heating system, the water-saving
plumbing fixtures. A moderately conservative person might use around 50
gallons of water indoors. Outdoors, the sisters plan to leave the
landscape in a natural state, so they won’t be using much water
outdoors. However, they have installed a pool/spa that holds 1,500
gallons of water. Once it’s filled, it will need to be replenished
occasionally. And the sisters do anticipate occasional long-term house
guests. Installing the bigger 30,000-gallon tank has given them peace of
mind.
You might be asking about now, “But is it really feasible to supply
an entire household with its potable water from a rainwater harvesting
system?” Yes. Here’s what Chris Maxwell-Gaines of Innovative Water
Solutions had to say in a report to the lender’s underwriter:
For more evidence of the ability of
rainwater harvesting systems to supply an entire household with its
water, my company conducted a survey of about 70 of our potable water
system owners in 2012. We asked them to look back over 2011 which was
one of the worst year of drought since the 1950s. In 2011, our region
only received about 16” of rainfall. We found that only 30% of the
homeowners had to get water delivered during the year and a majority of
this 30% only had to get one water delivery. It is our best guess and
experience that due to the conservation technology of the rainwater
systems, property owners use a much smaller quantity of water since they
can directly see the entire supply of water for their household.
Contrast this with a home that is supplied by a well: The homeowners
can’t determine how much water is left in their well as they can with a
rainwater harvesting system. If the water level in their rainwater
cistern is getting low, they can proactively change their water usage
patterns in order to extend their water supply. The costs to top-off
their systems, which is a rarity, should not average more than a few
hundred dollars per year according to cost data received from local
water delivery companies in our region.
Question: “You mean, I can buy water for my rain tank?” Sure, you can
buy a little water if you need it, say a couple thousand gallons to
tide you over ’til the next big rain. You
can buy water and store it in a rain tank. You
can’t buy and store water in a well that’s gone dry.
Overall, rainwater as the sole water source for a home is more
sustainable, more durable, more secure, and less costly over time than a
well. Plus, you know where your water comes from and . . . you know
what? It sure does taste good.
Question: “What about financing?” It is possible to get financing for
a rainwater harvesting system as the sole source of water for a
residence, but it requires a lender who knows how to get it done. The
financing for the sisters’ project was arranged by
Green Energy Money,
whose appraisal process quantifies the homeowner’s return on investment
for energy efficiencies — and for rainwater harvesting. Security
National Mortgage Company provided the permanent financing. Plus, the
sisters’ home is in Hays County, which offers a property tax exemption
for water conservation initiatives, including rainwater harvesting.
Want to know more? Drop us a line, or leave a comment, and I’ll ask
Chris Maxwell-Gaines to weigh in and help answer any questions.
– Mary
See Solluna Builders, LLC
Resources page for links to more information about rainwater harvesting.