Septic tanks to cistern, will it work?

jamesbodellSeptember 27, 2007

I have sewer coming to my area within 2 years. I currently have two 1000 gallon tanks used for my septic system. I was thinking about using the tanks to supply water for my sprinkler system after I get hooked up. I aready have power to the tanks for a pump that is in there now. I figure the two side by side tanks would need to be connected near the bottom to allow water to balance between them. I would then need to add a jet pump(?) to power the system and connect to the in-ground sprinkler. My sprinkler controller already has an input for a booster pump, seems most of the sprinkler infrastructure already exists.

I would just tie my downspouts and water collection drain currently on the property into the tanks. The 4" drain pipe runs right past the tanks now, so that would be very easy. I would just have to figure out a water bypass to the water line if the tanks run dry.

BTW, I have about 7,000sq-ft of lawn.

Is this a waste of time with just 2000 gallons of water? It seems everything I read states cisterns about 7500 gallons and more. Will I use water at a higher rate than I can ever hope to replenish in the tanks? I live in NE.

Otherwise, I'll just fill the tanks with sand.


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Is this math off?

7000ft2*1/12ft(1 inch)=583ft3 of water needed to water my lawn with 1 inch of water.

583ft3*7.48 gallons water/1ft3=4363 gallons.

This means I need 4363 gallons of water to add 1 inch of water to my lawn, which is what is generally recommended. That would mean I do not have 1/2 what I need to water my lawn in summer. Am I missing something here in my assumption?

    Bookmark   October 3, 2007 at 11:42AM
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I expect you would want to pump and disinfect the septic tanks. Lots of bacteria in there that I sure would not want sprayed around.

Concur with comments about use restictions to a drip system vs a general overall landscape watering system and the drip may also be a bit more hygenic than a lawn sprinkler system at least until you get a few "flushes" of the septics.

    Bookmark   October 9, 2007 at 2:48PM
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To give you a point of reference for your calculations one acre is 43,560sq,ft and requires 2,715gallons of water for each 1/10 of an inch of rainfall or irrigation.

    Bookmark   October 16, 2007 at 10:46AM
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In my city, when they put in city sewer, they MADE the people have their tanks crushed and filled. Don't know why, but they did. You might want to check on that before you go to any expense with this.

    Bookmark   November 20, 2007 at 10:56AM
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The reason they have the septic tanks crushed and filled with stone is to keep someone from getting hurt 20 years later when the top collapses and someone falls in.

    Bookmark   November 21, 2007 at 9:19AM
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I also have an old septic tank that I have though about turning in to a cistern. My husband and I found it a few years a go. We were having pluming problems, so I thought we should investigate the area next to the house that does not grow grass. We dug down and lifted the lid to find about 3 feet of crystal clear water. I don't water much but it would be nice to have guilt free water. I can't bring my self to use city water for watering the lawn. Could someone post a if this has been done and what would be required.

    Bookmark   February 7, 2008 at 8:55PM
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I bet it would work great, but talk to a septic guy about getting it cleans and pumped out first. As long as you don't want to use it as a bath tub the plants will love you. Also change your sprinkler system to micro irrigation, so you use less water. This way that 1" amount can blow into the wind. A good rain would fill it up but also add an over flow line to let excessive water to escape. If you live in the out lying areas maybe hooking up a line into your toilet you can save water on each flush

    Bookmark   February 7, 2008 at 11:13PM
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>>I expect you would want to pump and disinfect the septic tanks. Lots of bacteria in there that I sure would not want sprayed around.We just had our septic pumped and had an informative conversation with the plumbing specialist. The bacteria necessary for proper septic operation only survive in an oxygen-free environment. Downspouts draining into a tank would eliminate this environment so septic bacteria likely wouldn't be a problem, would they?

Here is a link that might be useful: Our septic issue

    Bookmark   March 29, 2008 at 5:03PM
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I wondered how you would direct the water from the roof to your tanks; and how will you divert the water when the tanks are full?

We installed rain barrels last year and currantly have 1000-gallons total in 9 containers of differeing sizes (50-gal., 185-gal., 215-gal. at 5 downspouts) and it's enough water for the very limited amount of landscaping/plants we water and the small garden (22'x6'). Only occasionally do we have enough to apply to our postage stamp size yard (the grass in our front yard is approx. 22'x22' and the back right-of-way is 83'x10', and that's all the grass we have - we've eliminated everything on the sides and the rest of the back yard). Therein lies the key - eliminate as much grass as possible. Our yard is relatively new and we designed it with the least amount of grass possible.

We installed a diverter at each downspout. When the barrels are full, the water bubbles up into the diverter and it's directed out the downspout.

I had it figured last year it takes about 1-gallon per square foot in the garden, PER week, and we have two 50-gallon barrels (piggy-back to one downspout) located next to the garden. And you must remember, Mother Nature does ALL the figuring (LOL). It took about 1/4-inch of rain to fill a 50-gallon barrel.

We didn't run out of water last summer, but came close a couple times (we're located just outside of nowhere in the middle of Kansas).

Great job if you can get this to work for you!


    Bookmark   March 30, 2008 at 6:49AM
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Im looking into installing a 1000Gal septic tank for grey water from the baths and some sinks to pump back onto the yard also. If I install a drip system for the plants and I think there is also one for below the grass, Can a drip system clog up with grey water?

Im guessing we would install a fine screen filter between the house and the tank for hair and other gross stuff I would imagine might show up.

    Bookmark   April 14, 2008 at 6:08PM
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Due to the amount of land 3/4acre we will sit on and also that 1/2 the lot is on a 20ft slope Im going to need a tank to collect the split level water from the home. Also the tank will allow me to collect a couple days of grey water and pump onto the plants and grass. Either way I have to pump from somewhere and the tank will give the capacity required for a single watering. My current home is on 1/4 acre if that and drinks some 500 gal just for grass each time I water.

    Bookmark   April 15, 2008 at 8:12AM
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