Which is better septic tank: Plastic or Concrete?

Discussion in 'Homesteading Questions' started by highlands, Oct 14, 2006.

  1. highlands

    highlands Walter Jeffries Supporter

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    I'm trying to figure out which is the better septic tank material, plastic or concrete? Which will last longer and be more problem free? They both cost about the same. One advantage of plastic is I can lift it with my tractor. The concrete tanks are much heavier.
     
  2. sullen

    sullen Question Answerer

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  3. RedneckPete

    RedneckPete Well-Known Member

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    Usually the company providing the tank will deliver it with a crane truck, and will place it in your hole for no extra charge, provided the hole is ready when they get there. I don't know of anyone who has ever moved an existing septic tank, so I can't see the weight being an issue. Digging out and moving an existing septic system or tank has got to be the ultimate sign of poor planning.

    I'd go with concrete, I'm pretty sure it would be stronger and thus longer lasting.

    Pete
     
  4. The Paw

    The Paw Well-Known Member

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    I don't know, I think today's plastic tanks are engineered to be plenty strong, and I have never heard of one cracking.

    My next door neighbour has a concrete tank that developed a crack, and in a wet year, the tank kept filling up with surface water, triggering the pump and overwhelming the septic field. Granted, the tank was probably installed in the 1940's, so today's concrete tanks are probably less likely to have this problem...
     
  5. Daddymem

    Daddymem Well-Known Member

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    With the plastic, you have to worry more about floating than concrete so if your groundwater is high I'd be concerned. Bouyancy can be overcome with a concrete pad attached to the tank if you really want to use plastic in a high groundwater situation.

    As for the Presby system, as an engineer I gotta give them the thumbs up.
     
  6. ET1 SS

    ET1 SS zone 5 - riverfrontage Supporter

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    We have a plastic one.

    The truck driver and I were able to lift it and take it off the truck by our selves. Then I was able to move it around to where I wanted it, and my DW and I moved it into place when the spot was ready.

    A plastic 1250 gallon tank can be lifted and moved by two or three guys. One guy can lift a end and swing it around, by himself.

    You can not do that with concrete.

    I also cut a extra 2" hole in the top and installed a pipe going down the 1" off the bottom, and I capped that pipe with a threaded cap. So in the future I can easily pump it dry by myself. Obviously you would want to be flushing it while you pumped it.

    :)
     
  7. Cabin Fever

    Cabin Fever Life NRA Member since 1976 Supporter

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    As was said in an earlier post, a plastic tank is bouyant. But remember, it is only bouyant when it is empty. So, if you are in a high watertable area, make sure you fill your tank with water right after you install it and right after you have it pumped. A plstic tank also doesn't have much strength with it is empty....so keep if full of water. Never ever, drive any equipment over a plastic tank.
     
  8. FarmGoddess

    FarmGoddess Well-Known Member

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    My husband, bless his heart, installed the biggest honking concrete septic tank he could find. It wasn't cheap, but the guy that installed it has been around for ages (second generation family business) and says he's never had a problem with any of his tanks which are made with conrete over rebar wrapped in chicken wire. Says his dad got the idea from looking at plans for fallout shelters back in the fifties.
     
  9. highlands

    highlands Walter Jeffries Supporter

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    Ironically, in our case it turns out we have perfect, deep soils in the area for the septic leach field. I had not expected that. This is ironic because we live on a mountain in Vermont. . We don't even have to haul in gravel, just put in leach pipes and back fill according to the septic engineer. He was quite surprised. Originally he had talked about us doing a presby system but then he did the test pits and was down 7' and saying how wonderful the soils are.

    So the question is the tank rather than the leach field. Plastic or cement. I'm curious as to people's experiences or if anyone knows of studies about the different tank types. I am tempted to build my own of FC but have a lot of other projects on my plate. The septic engineer is very unhappy that I would even think of doing the tank myself - and no he doesn't sell tanks, just the design which doesn't specify which tank to use.

    Cheers,

    Walter Jeffries
    Sugar Mountain Farm
    Orange, Vermont
    Pastured Pigs & Sheep
    http://SugarMtnFarm.com/blog
    http://HollyGraphicArt.com
    http://BlackLightning.com
    http://NoNAIS.org
     
  10. Spinner

    Spinner Well-Known Member

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    There's an old concrete one on our property that started leaking before we bought this place. It was replaced with a plastic one over 15 years ago. We've never had a problem with the plastic. I don't have any idea how long the concrete was here or why it started leaking (maybe someone drove over it with heavy equipment or it just cracked with age?) I don't know how long the plastic was here before we bought either. The place down the road has a concrete one too. It's cracked and whoever buys that place will have to put in a new tank. I don't know if these tanks are super old, or if concrete doesn't hold up well in this part of the country. Everyone I know who has put one in over the last few years has used plastic.
     
  11. durangoranch

    durangoranch Active Member

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    As long as you make sure that the plastic tank is designed right( With dual chambers ) you should be fine. They are a lot lighter and easier to deal with.
    As with any tank,concrete or plastic, will float from the hole if it is not filled.
    Just check your forecast for the day. Also make sure the outlet pipe extends to w/in 6" from the bottom of the tank(inside).
     
  12. agmantoo

    agmantoo agmantoo Supporter

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    When sludge builds in the bottom of the tank do you think that you will have enough suction with your pump to get the pumping started? I doubt it.
     
  13. ET1 SS

    ET1 SS zone 5 - riverfrontage Supporter

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    Agmantoo- You don't think that a 5 horse ag pump could take a suction on it?

    Okay, maybe not. For the price of 20 foot of pipe, I do not think that I have made a huge mistake if it does not work.

    The location that I have setup to do the suction from is about level with the bottom of the tank, so the pump will not be working against any head. It will not have to perform a dead lift.

    How many horses do the honey trucks use to suck when they do the sucking. They commonly drop in a 3 inch hose to almost the bottom and suck away. then the really good services will spray a high-pressure stream back in the tank to stir and mix-up the sediment in the corners, to be able to suck it out.

    :)