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Calcite clogging septic tank outlet filter?

Post in 'DIY and General non-hearth advice' started by MJS, Oct 31, 2013.

  1. MJS

    MJS New Member

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    I have acid well water (5.5 pH) with sediment, so I have a main line water filter, an acid neutralizer and a water softener. I add about 40 lbs of calcite to the neutralizer tank twice a year to keep the level between 50 and 75%, and 40 lbs of salt to the water softener every 3 weeks or so. Both tanks backwash into the house drain pipe. There's a Zoeller(?) filter in the septic tank outlet pipe which clearly does its job. The filter routinely gets clogged with white-ish pebble-sized pieces. Is that from the calcite? If it is, what can I do about it? We're very careful about what goes into the septic tank. The filter first clogged about 10 months after the house was built in '03. Since then I'm lucky if I can go 3 weeks without cleaning the filter, all year round. I check it at least once every 2 weeks. It's been this way for years. Thanks for any insight and suggestions.

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  2. semipro

    semipro Minister of Fire

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    What type of salt are you using for the water softener?(CaCl, NaCl, etc.)
    What is the flow order of the neutralizer and softener systems? That is, which one flows into the other? I suspect neutralization occurs first but wanted to check.
  3. MJS

    MJS New Member

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    Thanks for the quick reply. I use straight NaCl (typically from Home Depot - blue bag, either Morton Salt or Diamond Crystal), and fine calcite for the neutralizer. And yes, the neutralizer flows into the softener.
  4. burnham

    burnham Member

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    I don't know anything about this, but my buddy that owns a septic service hates water softeners and powdered Tide detergent. I know he said Tide would clog the baffle, not sure about what his beef with the water softener was.
  5. semipro

    semipro Minister of Fire

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    I have enough knowledge of aquatic chemistry to know that its complicated.
    I asked about the salt type and treatment order thinking it would give some idea of the reactions occurring. It didn't really so I've read a bit on the web.
    A couple things I read stand out.
    The first is that calcite alone is seldom recommended with pH below 6.0. With more acidic water (lower pH) it is recommended that magnesium oxide (Corosex) be mixed with calcite for proper neutralization.
    The 2nd is that the issue of salt laden water softener backwash effects on septic are controversial. Some contend that the introduction of high density salt water into the tank displaces sunken solids allowing them to flow out, clogging the drainfield, or in your case, the outlet filter. This seems reasonable to me.
    I also can't help but wonder if your softener is not over regenerating the column in that its washing much more salt water through it than is needed for regeneration.
    No sure answers here but maybe this will bump your post and someone that know's something will chime in.
    Good luck.
  6. Highbeam

    Highbeam Minister of Fire

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    I am all set up to install my water treatment equipment. I have a septic and the LAST thing I would want to do is run all of that backwash and regen water into the septic system. Flush that junk out into the grass somewhere. These things backwash every so often for 14 minutes at 5-10 gpm. That's a lot of water not to mention the funk being backwashed. A normal house uses about 200 gallons per day so the extra 140 per device is like dumping another house into your system.

    I doubt that the treated water is your problem, it's that nasty backwash with all the funk plus the high loading of waste into your septic during a backwash.

    Can you divert the backwash waste? Even for a few months to see what happens?
  7. MJS

    MJS New Member

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    I would have to poke a hole through my outside wall or dump the backwash into my sump pit.

    Update on the pH- I used a test strip I bought today from Home Depot: untreated: <5, treated ~6. Also, the whitish pebble-sized pieces that clog the septic tank outlet filter turn to powder when dried and crushed.
  8. Highbeam

    Highbeam Minister of Fire

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    Poke a hole or use your sump pit. It is silly to run this concentrated nasty stuff into your septic system.

    Why can't you get your pH up to neutral? Even at 6 it is quite acidic and will dissolve copper. I've had to fix city water systems that were making 6.5 water and causing pinholes in the plumbing along with excessive discharges of dissolved copper from the sewage treatment plant. I used caustic soda injection (NaOH, aka lye or sodium hydroxide) to raise pH.
  9. semipro

    semipro Minister of Fire

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    Agreed, 6 is too low. The pH scale is logarithmic so pH 5 water is 10 times as acidic as pH 6.
    As I mentioned above it seems you could easily add some magnesium oxide (Corosex) to your system to raise you pH to 7.
    Neutralization processes creates "salt" as a byproduct. You're also adding salt to your system when you regenerate your softener column. That's a lot of salt for a septic system to handle.
    Last edited: Nov 4, 2013
  10. homebrewz

    homebrewz Minister of Fire

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    Interesting problem. There are some places where the geology can't buffer out the acidic rainwater that recharges the groundwater.
    How deep is your well, and do you know what its completed in? Sand and gravel, or bedrock? If bedrock, do you know what type?

    I don't have much to add, except that the whitish stuff is probably one of the byproduct salts from neutralization.
    In your case, its either calcium chloride or calcium sulfate.

    Calcite is a slightly weaker base compared to magnesium oxide, so magnesium oxide should do a better job of mopping up the extra acidity.
    If you can neutralize the acidity more efficiently, you may see less byproducts clogging the filter.
  11. TradEddie

    TradEddie Minister of Fire

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    The Corosex (also called NS Mix when pre-mixed with Calcite) has other advantages too, it adds less hardness to the water, much less gets consumed so you need to refill less often. It does cost more, but I think in the long run it works out less expensive. Finding a retail supplier is the only problem. Do not use pure Mag Oxide, it will cake up and clog.

    A properly operating neutralizer should not be adding salt to the backwash water, the "salts" (not sodium chloride) it produces stay in solution (adding hardness), only the softener regeneration would add salts, the neutralizer backwash is really only to flush out particles because it acts as a depth filter too.

    TE
  12. MJS

    MJS New Member

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    Update- the water treatment company man came out and tested my water. From the well it's 5.5 pH, at the faucet it's 7, as it was when they installed the system 10 years ago. (So, don't blindly trust the $10 water test kit you can buy, it said both numbers were lower.) Like everyone else I've talked to, he hasn't seen this problem before. I'll have those whitish pieces from the septic tank tested at a lab to see what they are. I poured vinegar on some dried ones and nothing happened - didn't bubble (bubbles would indicate calcium) or dissolve. They turn to powder when crushed.

    My acid neutralizer back washes every 6 days, about 50 gals per cycle. The water softener back washes every 1500 gallons, also about 50 gals per.
  13. velvetfoot

    velvetfoot Minister of Fire

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    Do you know the hardness of the water? It seems like a lot to me, but our water isn't that hard.
    Not that it has anything to do with it but do you use the crystals? In the softener brine tank I've had better luck with crystals rather than pellets, as far as clumping. I've heard that the pellets are formed as the byproduct of some other product, not sure what.
  14. Highbeam

    Highbeam Minister of Fire

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    Interested to see what the lab comes up with. Calcium, magnesium, etc. what makes you think that it would bubble with vinegar? By the time those minerals precipitate out and form that white junk they are a salt and at equilibrium If the calcium was pure and unbonded it might fizz. Vinegar is an acid and since your water is so acidic, I doubt that additional acid would create a reaction. Septic tanks are quite acidic as well due to the stuff you add to the water before dumping it. Put something basic on there and you might see a reaction. Got any lye?
  15. homebrewz

    homebrewz Minister of Fire

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    Effervescence is the classic reaction of a carbonate with acid, and usually hydrochloric acid is used. I'm not sure if vinegar if strong enough to promote a reaction. Maybe if its heated. I'm guessing you have some kind of sulfate product showing up, maybe CaSO4 or MgSO4.
    Swedishchef likes this.

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