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Underground holding tank

  1. May 25, 2009 #1
    I wish to build an underground water holding tank. It will be 12’ wide by 12’ long by 10’ high. It will be constructed out of reinforced concrete.

    My figures show the box to be 1440 cubic feet, 10,771.2 gallons, and 89,827 Lbs. or 44.91 tons. The container will be buried in the ground with a concrete top to it.

    My question is, how thick will the walls need to be, and the floor. What would the pressure be on the walls?

    I am not sure of the cost of construction, or just to bury a tanker truck.
    Thanks for your answers.
  2. jcsd
  3. May 25, 2009 #2
    I like your thinking, I have the same idea: here are some concerns I have recognized, in my own design.
    a. need to filter the water, prior to storage, to eliminate debris--then need to deionize the water, to prevent breakdown of the concrete. One must also distill the water, after storage, before consumption, to remove the inorganic impurities which have accumulated, over time, as the water sits in the concrete storage tank.
    2. must have a drain at the bottom of the tank, with a valve, for cleaning, especially, after treatment with either basic or acidic cleaning agents.
    3. Concrete cover seems unreasonable, to me, because of the need to access the interior for cleaning.
    4. For me, I have three tanks: one in use, one for storing the filtered water, one for storing the filtered, deionized water. The question arises, which material reacts least with water, over time:
    Obviously, concrete will be least expensive. But, over time, is concrete a good container? How will the exterior of the concrete be treated, so as to ensure that none of the soil chemicals/microbes, penetrate, via cracks, into the stored water?
    I am much more concerned about the chemistry of concrete + water, than in the civil engineering questions about loading forces...
  4. May 25, 2009 #3
    Thanks for such a quick response! My water supply will come from a spring near the house. I have a 300-gallon tank I put on my truck for transport. I have a 3 filter system on the house now, and plan on same for tank. Will draw water from tank and filter then put back into tank thus circulating the water. I have plans to capture ground water, and run it through a gravel pit, and 2 sand pits, treat and put into holding tank.

    I can install a drain in the bottom of wall, but did not think of that! Thanks! The top will have a manhole cove for getting into the tank. I want to make sure this is sealed rather well. I have priced PVC sheeting to line the inside with, but is not cheap. I plan on using a sealer on the outside of the tank, and then using a spray on “tar” to seal. I treat my water with chlorine, ¼ cup per 1000 gallons.
  5. May 26, 2009 #4
    umm, good.
    I am of the opinion, maybe not widely held, maybe at variance with the National Institutes of Health, or the Center for Disease Control, but, in my opinion, adding chlorine to water stored in a concrete tank is a mistake.
    Your concern is understandable, you wish to control bacterial infestation. Admirable
    However, in my opinion, not, by any stretch of the imagination, an opinion shared by anyone else, you err in adding chlorine, or any of the halides, to stop bacterial overgrowth. Yes, you will eliminate infecious agents, but what about the chemical reaction with the concrete, or the PVC?
    I prefer de-ionization, first, prior to storage, (after rigorous filtration, as you have described) and then distillation, prior to consumption. This has the same effect, i.e. eliminate the harmful bacteria, but does not induce harmful chemical reactions with the concrete, over the several decades which the concrete tanks will function.
  6. May 26, 2009 #5
    I did not stop to think of the effects of chlorine and concrete.
    Just one more thing to pop up in the never ending quest for knowledge.
    I know from when I talked to the sheet PVC guy it would be ok with the chlorine, but that was a while ago, and do not remember if it was a particular type of sheeting.
    After reading about the swimming pools, I thought about maybe plastering the container, just like a pool. I just can’t see myself brushing and Vacuuming the container. I am using a 1000 gallon plastic tank for holding. I have been using the ¼ cup per tank for 5 ½ years not with no ill effects of tank. You have me thinking now, but that is ok, as it gives me something to do! Thanks.

    (this is from a water treatment plant in Il. On its distribution pipes)
    Chlorine disinfectants can dissipate dramatically within distribution systems.
    The results of this study showed that an average of 23 percent of the free chlorine loss could be attributed to wall reactions with concrete pipes
    Since the finished water is very low in organics, the wall reactions can be attributed directly to the concrete materials.

    (this is about the reaction of chlorine and concrete for swimming pools)
    Some websites on swimming pools (www.poolinfo.com[/url] and [url]www.caromal.co.uk[/URL]) gave the answer. The solution in a swimming pool is a complex buffered solution. It contains chlorine, but the other buffer chemicals (should) keep it in a slightly alkaline state with pH of about 7.5 . In this state the concrete is not attacked.

    There is some debate as to the potential for chlorine presence to somehow assist in the formation of carbonation, which does weaken the affected areas by matrix deterioration. My opinion is that a reduction in pH of the concrete due to the presence of very weak acidic reaction is the culprit. ( sounds like if you keep an eye on the pH it will not destroy the concrete)
    Last edited by a moderator: Apr 24, 2017
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