POLL: Septic-to-cistern conversion banks rainwater for irrigation

Marco resident reports success

Article Highlights

  • "Imagine if there were 1,000 Marios on Marco. You could be saving 11 million gallons of water a year.” Mario Sanchez

Do you think converting an old septic tank into a cistern to save drinking water is a worthy endeavor?

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Marco resident and business owner Shannon Cain explains how the septic tank turned rain water cistern works, while proud owner Mario Sanchez, Councilman Frank Recker and Councilman-elect Joe Batte look on just prior to a city inspection Friday.

Photo by KELLY FARRELL, Staff

Marco resident and business owner Shannon Cain explains how the septic tank turned rain water cistern works, while proud owner Mario Sanchez, Councilman Frank Recker and Councilman-elect Joe Batte look on just prior to a city inspection Friday.

— Seeing his sprinklers water his yard feels great, says Marco resident Mario Sanchez. His home is among the first on Island that won't waste as much treated drinking water on the lawn.

Sanchez celebrated the completion and approval of his septic tank to cistern conversion on Friday at his house on San Marco Road. After a long struggle over local regulations, he has a system in place that captures rainwater from his roof via the gutters, stores it in a 1,400-gallon underground tank, and uses the water for landscape irrigation.

“Every gallon we use is a gallon of water not taken out of the aquifer,” Sanchez said. He calculates his sprinkler flow at 90 gallons per hour.

Sanchez, who has a Ph.D. in computer science and is a tenured professor at Miami Dade College, jokes: “I’m the smart kind of doctor.” He adds that the ecological benefits of his setup were the primary concern.

“I have always been a steward of the environment. That’s who I am,” he said. “When we hooked up to the city sewers, we were ordered to destroy our septic tank. I thought, ‘why not use it as a cistern?’”

Initially, he said, the reaction from the city staff was not encouraging. “The feedback from staff was, ‘no, no, no, no, no,’” he recalled. “They had ridiculous, stupid numbers for the cost.”

But Sanchez persevered, and got several city council members interested in his idea. Working with contractor Shannon Cain of Cain’s Bobcat Service, he got permitting, and a unanimous approval from the council to waive the permit fee.

First, he said, the septic tank needed to be emptied, as must be done for every tank, whether it is being destroyed or converted. Then, the tank was disinfected, inspected, and pipes were run from the downspouts on his gutters to fill the new cistern with rainwater.

For the final step, connecting the cistern to the sprinklers, Sanchez created an innovative technique.

“My design does not use electricity or a pump. I use a system developed by the ancient Romans,” he said. “It’s hydrostatic. When you go from a wide pipe to a narrow pipe, and back to a wide pipe, it creates suction, a natural vacuum.” He credits Marco Public Works Director Rony Joel with providing a key piece of the puzzle.

“Rony Joel came to a meeting and said, ‘Hey, that’ll work. I know where you can get that injector.’ We’ve been testing about a week, now, and every test has been beyond our expectations.”

Cain said he was surprised by how effective the system was. “Mario’s is the first to use that style to pull water out of the tank. It’s pretty unique. I knew it would work, I didn’t know how well.”

He learned a lot in the course of putting the apparatus together, and hopes many more islanders will use a similar system.

“If you’re eco-conscious, want to use less drinking water, and still have green grass, this is a great way to do it,” he said.

Cain estimated the total cost at around $3,000 for the entire operation, versus roughly $2,000 to simply drain, crush and fill a septic tank. Although a previous grant offsetting the costs did not materialize, there is a prospect grant money may become available in the future, he said.

What has taken most time is the paperwork, said Cain. The actual installation, he said, can be completed in about 10 days.

Doing some of the work himself, Sanchez figures his total cost was under $500, and hopes to see his systems replicated all over the island.

“I hope they can take this as a spark. Imagine if there were 1,000 Marios on Marco. You could be saving 11 million gallons of water a year,” he said. He has posted a journal of his project on the web at marcoislandblog.blogspot.com, with photos of the installation and video of water pouring into his cistern. Click here to see the blog.

There are several thousand homes on Marco Island where a septic tank is being replaced by a sewer connection, making them candidates for a system like his, said Sanchez.

Cisterns are common in the Caribbean, for drinking water, not just irrigation. On Marco, Island Automotive owner Keith Pershing and musician JRobert have also done septic tank to cistern conversions, although Pershing uses electricity and JRobert uses a hand pump to deliver the water, said Cain.

So when the next rainstorm pours off your roof, keep in mind: you could be saving the water, and using it to save the planet, one gallon at a time.

Click here to visit a Web site by Shannon Cain if interested in using your old septic tank to store water for irrigation. Or call Shannon Cain, 229-2337, for more information.

Kelly Farrell contributed to this report.

© 2010 marconews.com. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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Comments » 5

sharkfloss writes:

Congratulations on you cistern installation. But please do not obfuscate some of the facts.

1.In a month of dry season you were able to save on 1400 gallons 2 times. In rainy season you will fill the tank and it will stay filled for a long time because it will not be needed and the rain will take care of the watering. Have you really figured how many actual use to fillings your system will do thru a complete yearly cycle. I did some time ago and it was not that many as to save, in quite a few years, the average cost of installion, which was posted by a city council member at that time. My calculations figured about a 15 year payback. (Figures upon request).

2. I calculated that my whole system uses approsimately 1200 gallons per watering cycle. This means that your two fillings of 1400 gallons each will cover 2 plus waterings. What do you do for the other 6 waterings a month? Do you not water or do you use city water?

In my opinion this by no means a money saving proposition for the average homeowner who will not do most of the installation work him/herself. Now one has to consider future repairs for two systems, the original and the cistern.

Bottom line:

Good for the environment. YES
Money Saving......VERY DOUBTFUL

Marconian writes:

I agree sharkfloss, and lets also rule in the fact that this dry season had an unusual amount of moisture not seen in decades.In a normal dry season there wouldnt be any savings.

sharkfloss writes:

Please read and consider prior to voting in the above poll. There are two parts posted.)
There are several assumptions and calculations that each one of us should make prior to conversion of septic to cistern.
The first assumption is that it rains here on Marco the same as it does in Naples. In the several years that I have lived on Marco I can not count the times that I watched the storm clouds pass to the East of Marco and rain profusely in Naples and here on Marco there was very little or no rain at all. This is important because the calculations we have generally been given are based upon the amount of rain in Naples. (Calculations below are based on average S.W. Florida rainfall and therefore produce a greater savings than here on Marco.)
The second assumption given was that an inch of rain produced approximately 1288 gallons of water that could be used for irrigation if it was routed to a cistern. This assumption could work during the months of January through May and then again October through December. In those months I calculated the maximum potential rainfall as posted on the internet for Southwest Florida would produce enough rainfall for approximately 19 waterings. During these months there could be 19 inches of rain. This assumption does not take into consideration what happens to the rainwater that occurs when the cistern is filled up. Once the 1,400 gallon tank is filled the remaining water has to be routed elsewhere. This means that the 19 potential waterings gets reduced by the amount of times the tank cannot hold any more water. Let us say this happens only three times. Now we have 16 waterings to save us money. Also consider that the 1400 gallon tank does not get completely emptied as there will most likely be residual water left below the pipe line. Now we have to calculate for the rainy season, which is June through September. During this period we have 33.5 inches or rainfall in Southwest Florida. I don’t know about everyone but during these months my irrigation system hardly gets any use. Why? There is enough rainfall during that time, which averages over 8 inches per month, to not have to use the irrigation system much at all.

sharkfloss writes:

The third assumption is that all of this water gets calculated into savings if it goes into a cistern.
The trouble is your tank only holds at most 1400 gallons which tends to stay in the tank because it has already rained enough so the irrigation system is not used. In reality it may only get used three times per month if and only if the dry days get too far apart. You also have to remember that once the cistern is empty your city water has to kick in to take up the slack.
Now let us do the calculations using this information as a basis. Sixteen waterings during dry season; 12 waterings during rainy season give me a total of 28 waterings that could counted as savings generated by a cistern. If one uses 1,200 gallons per watering multiplied by 28 you have a total of 33,600 gallons of water saved. Let us now calculate that at the present rate of $3.48 per 1,200 gallons your savings come out to be slightly over $97 (28 x 3.48) per year. Remember that this takes the average rainfall of Southwest Florida and not what actually occurs here on the island which by my experience has been less. Also take into account the $25 lost in interest each year from the initial $1000 investment. This leaves us with a yearly savings of $72.
Final assumption: Cost of conversion could be about $1000+. This does not seem to include added pumps, electrical work that may be necessary on individual job site situations which would ultimately increase this cost. But, for argument’s sake take the $1000 as the actual cost divide that by $72 savings per year and I come up with 13.9 years to recover the initial expense. If the system conversion costs more than $1000 the number of years will be increased proportionally. None of these figures take into consideration general repairs to the system over the years. I do not think that this would be a prudent investment decision for most people. Let’s hope that our cost of water does not increase to make this a make this plan a fiscally reasonable plan.
If one is considering environmental concerns of water usage that decision would be up to them. But financially speaking it does not work for me.
Green for the environment: YES
Green for your wallet. NOT SIGNIFICANT

sharkfloss writes:

Correcton: Calculation was done on $3.48 per 1000 gallons not the 1200 as previously posted.

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