I’m contemplating building a couple of cisterns to catch rain water to use for summer irrigation. They would be underground and covered. I can get plastic 1,000 gallon tanks for about $1,000, but I’d like to hold somewhere around 5-10,000 gallons.
I’ve considered the following ways:
1. Poured concrete.
2. Concrete block.
3. Plastic tanks.
4. Less common “alternative” holding methods.
Criteria for choice of material/technique will be a combination of how much water I can hold, price per gallon to hold it, labor to install, “being leakproof”, ease of cleaning, and long term soundness.
I got quite a few recommendations here a few weeks ago about using dry stack retaining wall blocks for retaining walls. That got me to wondering if I could dry stack a round “tank” (sort of like a kiva) and line it with some sort of poly or other sheet material that would actually hold the water.
I’ve never built a concrete “roof” and would like suggestions about how to go about building a roof or top over the tanks. I considered pouring slabs with rebar in them that I could move with a backhoe to set over the tank after curing. I’ve also considered building a temp form deck to hold the concrete in place until cured. I could also use steel beams, but I imagine that would cost extra.
Maybe I’m crazy (Hey! I heard that!), but I’d like to be able to park a car on top of one of the tanks.
I think it’s worth it for me to do this due to my own and my wife’s love of gardening and horticulture. We live in a place with average annual rainfall of around 14-18 inches. In drought years the town we live in bans outdoor watering or drasically restricts it.
Thanks in advance for all suggestions, thoughts, and experiences with cistern building!
Joe
PS – I did read the article in FHB about the giant cistern in Texas.
I’m thankful for the loyal opposition! It’s hard to learn much from those who simply agree with you.
Replies
I like the concept.
The big problem that I have is that the drystack modular retaining wall blocks are not designed for a large overhead load like that.
I think a lot will depend on compressive load carrying ability of the soil that is behing the walls.
I have always wanted to bury a stainless steel tanker trailer to use as a cistern. I you find one for sale, buy two.
What about shotcrete?--dig hole, put in rebar and meh and then have shotcrete done. For a lid, you could do a similar thing with like catenary cables fastened at edge of hole--gravity would pull them into the proper shape, put some steel mesh on top and then do shotcrete. After curing, lift them out and flip them over. Don't know about supporting the weight of a car. Probably some engineers will respond to this shortly.
Air-placed concrete (aka: Gunite and Shotcrete) is probably the best idea; however, it is very porus and requires an impervious lining, usually medusa cement (like stucco with marble dust in it) and then a swiming pool liner. You have to decide early on if you want to have drains/permanent plumbing in the cistern, or, just use a "straw" or a submersible pump. Go deep and narrow to keep the structure strong.You need an engineer for the roof if you're going to put cars on it. Especially if you want an access hatch up there too..
Phill Giles
The Unionville Woodwright
Unionville, Ontario
In the fall of 03' I assisted a local organic farm design, build/install a ~8000 gallon cistern set up and a 12'x24'x8' (~16,000 gal) root cellar with a concrete top that was designed to carry a 3' depth of heavy clay plus a medium sized tractor w/ implements.
The cistern was constructed of 4 manufacured concrete cistern tanks (1950 gallon each@ $750 delivered) set in an offset manner to a 16' poured square foundation excavated into the side of a hill, which left a 6x8' center well pit for pump, fittings and etc/ The center pit area was laid up with block to ground level and contains a hatch to service the pump & plumbing. Actual access to each cistern requires excavation at each portal.
The whole area was covered with clay soils to a depth of 2'. It is mown over with a ford 8n tractor/woods mower...light loading.
The root cellar was made of surface bonded block and then rebared and filled with concrete...the roof was poured concrete 12" thick with lots-o-rebar. It was designed to carry lots of load ~300#/sf.
Although the root cellar has an entry at one end....your application would see a cast concrete wall at the total perimeter and a cast roof very similar to what we did at this site.
I also explored the use of tanks from http://www.plastictanks.com and American Tank Company. Plastic tanks were limited in size and were not strong enogh to backfill over.
American tank company products are spun fiberglass and designed for large volumes and burial.......also BIG $$$$$. A 10K gallon tank was $13,000 and required a ballast concrete pad w/ straps, plus specified fittings and etc. which were more $$$.
We opted for the precast tanks and lots of interlocking plumbing and valve....material costs exceeded $4400 plus excavation/backfilling. A linear arrangement may have been less $$ if a pump pit is not required.
Both projects have been in operation for over a year...no problems.
................Iron Helix
Thanks for the input. Now I'm leaning toward precast.I'm thankful for the loyal opposition! It's hard to learn much from those who simply agree with you.
Apart from the lid, what you're proposing is no different than building an in-ground pool.
I'd go with a poured concrete structure but that's only because I'm familiar with that type of construction. The top is no problem, I'd use rib-lath as formwork/reinforcement and have an access cover for cleaning.
Are you sure about the maximum capacity of tanks available? -- that seems very small. [I like the idea of burying a milk-tanker!]
IanDG
Ferrocement Water Tanks and Their Construction
http://www.amazon.com/exec/obidos/ASIN/0903031515/ref=pd_ir_imp/102-8914417-2884906
Good Book, Good Luck.
Let me preface this by saying I have no experience building cisterns, would love to have one for the same reasons, and I am not a certified engineer. That said...
instead of round or square, go long and narrow and or deep. The shorter the span side to side the easier it should be to get a strong roof on it. If you keep it narrow you could span it with steel beams or reinforced concrete panels.
Under a driveway done with pavers means you could uncover a section for access without ruining an asphalt surface. Or better yet build a set of stair off one end for access to a locked outhouse type structure. Just unlock and walk down to inspect.
If you did concrete block you could have the inside sprayed with Rubber-Wall foundation sealer. If it keeps water out it should keep water in. No?
Or if you come across a hundred thousand bricks you could build it like the London sewers.
In the long and narrow catagory: Buy a "Connex", a 40-foot shipping container. At $1,000 for a seriously ugly one to a maybe $5,000 for a pretty serviceable one (as a storage shed), it is a lot less than the rule-of-thumb $1/gallon*
Line it with plastic. Like 20 mil or thicker polyethylene sheeting. Bury it. Pump through a hole cut in the top. No need to span it, they'll easily hand a a couple of cars - I see them stacked 5 and 6 high. That like 200,000 pounds sitting on the bottom one.
In dry soils, it will last a very long time. In wet soils, get some really good paint on. Or bolt on a bunch of zinc anodes from the marine-supply house.
Heck, buy two. Stack them up. Use the lower one as a wine cellar.
*That is, by the why, a dang good rule of thumb: 5-gallon gas can? $5.99
10-gallon gas can? $9.95
1000-gallon tank? $1000 as you found.
Last study I saw on a large tank: 20,000,000 gallon tank: $18,700,000. They actually spent $300,000 deriving that cost estimate. David Thomas Overlooking Cook Inlet in Kenai, Alaska
David,
I don't know about the steel conexes, but the aluminum ones don't have any structural strength in the roof. They won't even hold up to snow loading in Anchorage. The stackability of those things comes from the steel frame. I know that the steel boxes have more strength in the roof, but I would still be concerned about driving over them. As a side note, I have been told that they do flex under the weight of a guy on there, so I would be somewhat concerned with loading them with dirt and equipment.
If you bury them upside down, however, the floor becomes the ceiling and you can carry at least 200 #/ft on those bad boys. I have one in the ground that way and it is as solid as the day is long.
Steve
I had been thinking along the same lines: deep, long and narrow. I tend to wing it with my own seat 'o the pants engineering and then live with the results. I haven't been dissapointed yet. (My low tech $100k passive solar home works about as well as my engineer buddy's $600k high tech passive solar home. hehe!)
I was also thinking about foundation sealers.
I'd hate to lose too much, but a little leakage wouldn't matter much.I'm thankful for the loyal opposition! It's hard to learn much from those who simply agree with you.
I did some research a few years back on home water tanks. I'm having trouble re-creating the search strings I used on Google and other search engines, but IIRC, the price per gallon on purchased tanks goes down as the tank size goes up, at least up to the largest sizes that will fit on a trailer. Also, used tanks are widely available and noticeably cheaper than new.
If you decide to build, keep in mind that bigger is better. The best simple tank shape, in terms of volume per surface area, is a cylinder with the height equal to the diameter. The volume of such a tank is 2 x pi x radius cubed, and the surface area is 6 x pi x radius squared. Compare a 10' tank to a 12' tank.
10' diameter and height:
Vol = 2 x 3.14159 x 5^3 =~ 785 cu. ft. =~ 6,283 gal.
Area = 6 x 3.14159 x 5^2 =~ 471 sq. ft. floor walls, and roof
12' diameter and height:
Vol = 2 x 3.14159 x 6^3 =~ 1357 cu. ft. =~ 10,857 gal.
Area = 6 x 3.14159 x 6^2 =~ 679 sq. ft. floor walls, and roof
So the larger tank holds 73% more water but only requires 44% more material.
If you decide on cast in place concrete, look at post-tensioning. My understanding is that it reduces the overall cost of reinforcing and keeps any cracks much smaller, making it a lot easer to seal.
I've seen some old ones that were circular and kind of conical, so they were 10-15 feet in diameter at the bottom and only 3-4 feet at the top. These, however, were made from limestone "creek stone", set in mortar.
How about pre-cast concrete septic tanks? They're strong and probably made in large enough quantities that the cost is reasonable. Plus, they already have holes for your pipes!
I think the typical residential ones are about 1000-1500 gallons, but maybe you could find one sized for a bigger building to get the volume you want.
Al Mollitor, Sharon MA
I'm not sure that I could get one in. Hill on one side and existing carport over part of the hole it will need to go in. Carport roof is only about 12' above grade.
The tanks you mention are commonly used around here for the purpose you suggest. Easy to install in most cases, but not cheap.
It would still be a possibility for my second tank, though. Thanks for reminding me of them.I'm thankful for the loyal opposition! It's hard to learn much from those who simply agree with you.
Joe,
How about burying a shipping container with a bladder in it? I would guess that you could get a 20 or 40 foot container in your area for a couple of thousand bucks and maybe a whole lot less. By using Uncle Dunc's calculations, I figure you would get about 10,240 gallons in a 20 footer.
One thing to keep in mind is that the floor is the strongest part of the container, so you should bury it upside down. Leave the doors on and cut an access hole through the wood on one end if you really think you might need to get in there.
I don't know what you would use for a liner - maybe check with the swimming pool guys around there. You could also check with anybody who provides tanks and see what they use for secondary containment.
Good luck.
Steve
Great example of how thinking outside the box could lead you back to a box. ; )
Thanks for the suggestion. A buddy just bought a container. Good idea!I'm thankful for the loyal opposition! It's hard to learn much from those who simply agree with you.
Have thought that a cistern would make a lot of sense. A few times I have dug around the web looking for information. In response to this thread I looked again and found a neat site:
http://www.lifewater.org/resources/water_storage.html
Lots of information written in a practical and easy to understand manner. Looks like this is possibly a good organization to give money to. Water is a concern here but in third world countries it is life and death.
Check out, from the same site:
http://www.lifewater.org/resources/rws5/rws5c1.pdf
Practical designs. Thought the 1000 gallon jars to be quite interesting. Something the kids could help build and the whole family have a good, but messy, time.
The reinforced concrete looks doable enough.
Next door neighbor is retired pro gardener, needed > 5000 gal cistern. He looked aroung and found a 5000 gal steel tank for $50 deliver charges only, never had had anything but food/water products in it. (Seattle area) Look around surplus sites in your area for similar deal, tha salvage yards do not want to deal with big tanks as they have to be cut apart first which is a $$ loser.
Buried it in a day, (he has a backhoe). Fills it from his shallow well in the winter plus all of house, barn, drive runoff.
Thanks, Lorn. Good links.I'm thankful for the loyal opposition! It's hard to learn much from those who simply agree with you.
Been doin my math lessons . <G>
My well in dry weather produces 1 gallon per minute with a 50 gallon capacity in the well. It fills a 500 gallon tank at the rate of 1 gallon per minute. 60 minutes x 24 hours = 1, 440 gallons per day! Septic tanks are rated here for an average of 6500 gallons per month.
So if you have any water table at all you could do it from a slight well.
Tim Mooney
The cheapest tank per gallon is a landfill liner. 60-mil polyethyelene sheeting (which can welded together in the field) is used to line a large hole.
Place one or more vertical well screens (PVC pipe) to hold a sump pump or electrical submersible well pump). Then fill with pea gravel. Porosity of about 0.30.
So a 30x30x12 excavation will take 400 yards of gravel, what about $4000 delivered. The liner would be about $800. Or careful bed it in sand and use 6 mil for about $90. Plus excavator time. So maybe $8000 for a 30 x 30 x 12 x 0.30 x 7.48 = 24,235 gallon tank. $0.33/gallon.
$0.20/gallon if you have sand or gravel on site.
And it is all ready to park on top of. No load limit at all and no time or money spent on designing and building the lid.
I built a house in an area with poor ground water and no municipal water. My solution was to put in three 1100 gallon water tanks and have them refilled every 2-3 weeks. They only cost @400 bucks each. They do make bigger ones. I don't know about cars on them though.
I havent read the thread .
We wouldnt spend the money here to build that big a deal for water storage. We would build a pond though and have some duckys. Why does it need to be coverd? If it leaks , put hogs in it and they will stop all the leaks after you run it dry. They will use it daily as it fills back up and seal it off. Pigs are pond contractors that get paid in corn.
Tim Mooney
It needs to be covered because of our climate. When it's 95 degrees, 12% humidity, sunny and breezy the water here "up" and heads for you at an incredible rate! I can also keep mosquitos in check with a covered tank. We have very few of them, but they can carry West Nile Virus. A buddy of mine, our undersherrif, got west nile and I'm afraid it took years off his life. He didn't die, but said he wanted to for a few weeks.
Also, I'm in town: no livestock allowed and not enough room for a pond
Upside: WE virtually never see a tick in town! Ticks last for about one month and are mostly concentrated in thickets of scrub oak.
Bill Clinton's not the only critter crawling all over everybody back there in Arkansas!I'm thankful for the loyal opposition! It's hard to learn much from those who simply agree with you.
Bill Clinton's not the only critter crawling all over everybody back there in Arkansas!
Lol ! Carry on then.
How much volume do you figure you need from rain to rain? I figgure you must be planning a truck patch garden at the amount of water storage Im hearing . Ive actually wondered about the same thing at my cabin , but the cost bothers me over 1500 gallons. Im not sure that 500 wouldnt water plants in a garden between on rain and the next.
Have you thought about a well? Or do yall do that either ? I can drill a well cheaper that would supply extra water . You might remember I put dynamite in my well and dry ice , but it still only supplies 1 gallon pr minute in dry weather. I run it though through a filter in a 500 gallon tank and it keeps up pretty well with more than I need. I figgure it would water a garden for me , but I havent tried it .
One more option you might consider is an above ground tank since you are using it in the summer. I think you can buy a 1500 gallon cattle water can for 3 or 4 hundred. They also sell plastic tanks for above ground . You would just drain them when hard freezes hits. Ive seen some barns water from the roof this way in feed lots.
Tim Mooney
Edited 2/13/2005 3:03 pm ET by TIMMOONEY52
Edited 2/13/2005 3:07 pm ET by TIMMOONEY52
I'd like to catch as much as I can. I can't drill a well here. We have just come out of a five year drought... how long til the next one? Don't know.
Most of our water falls as snow in the spring months. I need to catch then and hold over summer.I'm thankful for the loyal opposition! It's hard to learn much from those who simply agree with you.
Don't know the cost, but this is what you need:
http://www.containmentsolutions.com/products/underground_frp/nonpotable/index.html
I liked Dunc's post on the use of a round container and its material savings over rectangular containers. I wonder if the added labor forming two radius concrete walls would make that a wash in the end. Of course, if your labor was free.......
carpenter in transition
Looks good, but I doubt if it would fall into the "low cost" category.I'm thankful for the loyal opposition! It's hard to learn much from those who simply agree with you.
Cool site Tim . I bet its expensive.
But it looks like the ticket to what he wants if its big enough for him.
Tim Mooney
i have some very old (from the 1920's) homestead books they all show round concrete construction with a slipform ie: a pole in the middle of your circle connected to a wooden slipform box that you fill with concrete and push and fill with concrete you go up about 6" and maybe 10" thick? with each pass... and a cast in place concrete lid...you remove the supports for the pour after it sets up...they are very common in key west... but i'm with everyone else a poly lined hole ie: like a plastic lined pool seems cheaper & faster...
curious in your area how deep do they have to go for a well?
pony...
Wells here vary from less than 100 feet for a good well to over 1000 feet for a dry hole. (OUCH)
I personally participated in a dry 500 foot hole..... let's say it was disappointing.I'm thankful for the loyal opposition! It's hard to learn much from those who simply agree with you.
A dry 500 foot hole and the word dissapointing in the same sentence...I ain't even going there.As I understand it, there's a 40 foot aluminum shipping container available for free in Ft Lee NJ. But you gotta go pick it up...
The person you offend today, may have been your best friend tomorrow
At least we didn't have to case the dry hole.... it was blowing dust at 500 feet.
At a mere $10 per foot. For some reason I still don't like to think about it.I'm thankful for the loyal opposition! It's hard to learn much from those who simply agree with you.
I haven't read the whole thread, so forgive me if this is repeating...
There's a new in-ground water tank not far from here. It's concrete and was done by a company that brought circular steel form panels and a crane to the job.
First an excavator dug a hole that was roughly round, and about 20 feet deep. He also dug a ramp down into it, enough for guys to walk up and down. Then the tank crew showed up.
Day 1 they poured a slab floor.
Day 2 they set the forms on the floor and poured the first lift. Each lift is 4 feet.
Days 3-6 they removed the forms, raised them, and poured another lift.
Day 7 they poured a lid. They had a nifty steel form for the underside that they shored up inside the tank. There's a large access door thru the lid, and the forms came out thru that hole.
To finish up they installed a ladder to the bottom and a nice locking door over the top.
Who knows what this cost... $25-50K is my guess. It holds about 50,000 gallons.