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  1. #1
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    Rainwater tanks with high pH?!!


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    So hey again guys

    I have got some rather large tanks, one in the ground with no sunlight, testing about 100ppm and 8 - 8.5 pH... the other one in use is an IBC which has sunlight exposure and gets algae, this one tests 41ppm and very high pH, over 9. Does algae growth mess with pH?

    I have watched them fill a great deal with fresh rainwater over the last several weeks, and I have been using it on the garden, which seems to be working fine for the moment

    However I am seriously concerned about the why's and such of how it came to be so high when my freshly collected rain is normally about a 6 pH

    Does anyone have any answers or suggestions as to the how or why and whether I should continue to use it please?

    Much appreciated
    PO

  2. #2
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    Could be your roof runoff isn't arranged to not allow the first part of your water to flush the contaminants then fill with the follow on water free of roof and veg matter that might add to the problem. Pine needles I believe are acidic so a roof and gutters with them could taint the water a bit. Asphalt shingles might be acidic too so definitely clear the gutters and roof and any traps and don't use first rush of rain water. Being downwind of a city wont help things with car exhaust mixed into the rain.

    Good thing is a healthy soil can change the pH of high pH water.
    You stick a bunch of females together and don't want any problems? Good luck. They are going to mess you up.

  3. #3
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    Thanks @Tropical

    Yeah I did some more research on it, and whilst I haven't figured out the why of the high pH readings, I came across a fair bit of stuff that said for rainwater pH is fairly meaningless as the buffering capacity of rainwater is nearly zero, so it takes on the soil pH basically, immediately upon contact with the soil when you apply it

    Seeds pop in it, so I guess we are all right for the moment, but they did come out of the cubes looking kinda funky with pH ripple and warping of the leaves. Now they are taking it without further issue as they grow

    I'm still trying to pin down the exact cause; as you said, many of the things that may cause it to sway on the way to the tank would have it going in the acidic direction instead

    I'll update when I figure it out properly

    good times
    PO

  4. #4
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    Quote Originally Posted by Persistent Offender View Post

    I'll update when I figure it out properly

    good times
    PO
    As you spoke gremlins went hard at work to figure new tricks to play on you.

    Are you using strips or electronic pocket pH gizmo?
    Electronic hand held pH devices need calibration once in awhile like weekly or monthly. The sensor tip is supposed to be immersed in a storage solution when not in use. Cleaning the thing with the proper solution or distilled water is best. Any little thing throws the numbers given out off gradually getting worse if not cleaning it. Found out the tips wear out too so.......yah I've got a fancy one being delivered and didn't know a lot of what I am learning lately.
    You stick a bunch of females together and don't want any problems? Good luck. They are going to mess you up.

  5. #5
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    yeah i tried it with drops, colour strips, and with hanna pH meter. PPM meter was just a cheapo

    tested them all against vinegar; all tests function correctly... kinda puzzled?

    I dumped the last 100L or so from the algae infested above ground tank and rinsed it out, to get it to thoroughly dry out so we start with a clean slate and we can get her covered up so the algae doesn't bloom again. Probably I clean it with something nasty too before it rains again, but it doesn't look green anymore. The last 20L or so of the water looked like an absolute toxic green sludge

    thankfully the in-ground tank runs crystal clear, but still high pH

    I dunno

    we'll figure it out in the end eh LOL

  6. #6
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    Quote Originally Posted by Persistent Offender View Post

    we'll figure it out in the end eh LOL
    http://www.who.int/water_sanitation_.../rainwater.pdf

    If you love near the ocean sea water has a ph of around 9-10 so could be ocean spray mixed in there.

    http://forums2.gardenweb.com/discuss...er-is-alkaline

    Next batch see what amount of balancer it takes to adjust the ph. Hopefully the drains are clear and nothing is a factor and you get a great new start.
    You stick a bunch of females together and don't want any problems? Good luck. They are going to mess you up.

  7. #7
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    From the postings you kindly linked @Tropical:

    It is actually not important, because rainwater has virtually no minerals so it has no pH buffering capacity the way water from the tap or a stream would. Carbonate and sulfate create complex equilibria which require more acid or base to change the pH by a given amount than distilled water would (which is essentially what rainwater is, although it probably has traces of minerals from picking up dust). They resist changes in pH that have to be overcome.

    It takes almost no effort at all to change the pH of rainwater, and as soon as it hits the soil, it's going to take on the background pH of the soil.
    that's what I'm going with at the minute

    but yeah as soon as I have some fresh rain falling I will systematically figure out whether it's the roof, the tank, or the rain itself. It's not the ocean; landlocked country LOL

    cheers
    PO

  8. #8
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    Quote Originally Posted by Persistent Offender View Post
    From the postings you kindly linked @Tropical:



    that's what I'm going with at the minute

    but yeah as soon as I have some fresh rain falling I will systematically figure out whether it's the roof, the tank, or the rain itself. It's not the ocean; landlocked country LOL

    cheers
    PO
    Any good rain yet? How'd any testing go now?
    You stick a bunch of females together and don't want any problems? Good luck. They are going to mess you up.

  9. #9
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    yep I caught some over a week ago

    but the big tank wasn't run fully dry at that point, so ppm and ph are high on that one still, and I think the fresh rain stirred up any sediment because it ran cloudy for a few days after. Now I've run it dry so I'm gonna take the opportunity to rinse it out with some tap water at least to wash any remaining sediment off the insides of the tank before it starts filling again with the next rain

    the IBC container however was about right at 34ppm and around 6.5, although I think ideally it would be a little lower for both TBH, but maybe the tank was slightly polluted or something still from the hardcore algae, even though nothing was visibly green

    I cleaned the roof that leads to the tanks too, just in case LOL

    seems it was maybe the algae swinging the pH extra high, but I'm not really sure. apparently mosses on roofs lean to acidic, not alkaline, so I dunno if that could be the cause

    good times
    PO

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