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Thread: TDS Readings

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    GregNY's Avatar
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    TDS Readings

    Alright, exciting day for me as I finally received the TDS meter I've been waiting for to 'test the waters'. I've heard good things about water quality on Long Island so I was optimistic with it being low.

    I tested multiple locations allowing water to run for 10secs and had some interesting results:

    Kitchen Sink - 125ppm

    Backyard hose - 117ppm

    Garage sink - 98ppm

    Side house faucet (closest to meter) - 95ppm

    Filter water from fridge - 64ppm

    Now can I get away with watering my CP's directly from that side faucet without running in to trouble?? I believe recommended ppm is 50 but water consumption gets nutty on these 95% degree summer days here.

    Any recommendations greatly appreciated, at the very least now I know I can get 2gal out of every 1 gal jug I purchase.

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    Hello, I must be going... Not a Number's Avatar
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    One school says <= 100 ppm is safe, another says <=50ppm. So it's up to you.

    Flush out your pots and rinse your trays several times a year and change your media every two or three years (certainly no more than 4) and you should have no worries.
    Grand Hotel... always the same. People come, people go. Nothing ever happens.

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    GregNY's Avatar
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    I will await more opinions but that is very encouraging! I'm figuring at the very least I'd water from the faucet, and when it rains, it rains, and provides enough naturla flushing out as 95% of my plants are outdoors...

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    Hello, I must be going... Not a Number's Avatar
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    Temperature affects the readings too. Make sure the water is at "room" temperture or at least the same from your various sampling locations.

    If my tap water were <100ppm I wouldn't hesitate to use it. Unfortunately it's more around 300ppm.
    Grand Hotel... always the same. People come, people go. Nothing ever happens.

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    I'm actually running into the issue where TDS seems to be climbing in the days after I've added water to the tray... So, I've been rinsing out and changing the water (like a fishbowl) once a week or so... Is this PPM climb over time normal? Is this from the concentration of ions due to evaporation/absorption of water by the plants, or is it the active production of ions by algae, etc.? Or both?

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    The water is mineral-laden in some parts of the SF Bay Area; and I have drawn the limit I will use at 50 ppm. Some genera are more forgiving than others but anything significantly above that number affects the health of the live sphagnum I use for many composts . . .
    “Sì perché l'autorità dell'opinione di mille nelle scienze non val per una scintilla di ragione di un solo . . ."

    -- Galileo "Biff" Galilei

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    RL7836's Avatar
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    This is a recurring question on the various forums .... here's an old response I posted a while ago...

    This is a question that comes up frequently and typically the poster would like a yes / no response (wouldn't we all?). The answer I see frequently from 'experts' is 50ppm. Above 50 is questionable & below is 'safe'. I've also seen posts from people saying they grow plants well with 90ppm (D'Amato notes that 100 ppm is generally considered safe - but lower is better (Savage Garden pg 7)). From what I've seen, I don't think there is an easy answer (except for the cop-out: "It depends...").

    What does the answer depend on?

    - your growing conditions.
    --- are the plants growing on a sunny windowsill in a low-humidity house? Here you will be watering the plants frequently, the water will evaporate and the residual minerals will be left behind to concentrate in your media - quite quickly. This will produce an unhealthy media environment for the plants.
    --- are the plants growing outside in coastal Oregon or England? Here, the frequent rains will both reduce the need for manual watering and also flush the pots with rainwater to keep any minerals from being concentrated.
    --- how often do you replace your media (repot)? One nursery owner told me that his well water is full of minerals but the plants he doesn't sell get repotted with fresh media each winter and therefore continue to grow well for him.

    - species of plants.
    --- some species (like Neps) have somewhat of a reputation for being able to grow well with a wide variety of water purity. Some species of Drosera & Neps come from areas with limestone/dolomite and actually prefer hard water over soft. Other species are picky about their conditions and need everything just so ... I struggled to grow D. villosa (and did eventually give up). I changed many parameters but during this process, at least I knew the issue wasn't mineral-laden water....

    - you
    --- more specifically - your level of experience, your knowledge of the plants and ability to detect small changes early in the potential death spiral. Frequently new growers will post pictures of their plants infested with pests. More experienced growers will take a quick glance at the pics and see the pests while the newer grower never noticed and didn't even know what to look for. The changes that happen from mineral-laden water often produce a slow decline in plant health and can be especially difficult to notice. If you're aware of what to look for when tiny changes start to happen to your plants and you can easily rule out many other possibilities (like pests), you are much more likely to be successful with hard water than others who cannot detect small differences....

    - the actual minerals that make up the ppm
    --- I have heard that the well water in some areas of Texas & California have minerals that are not compatible with plant growth and may actually poison the plants. If this is true, I suspect that these conditions are rare and most would be aware of this condition before using the water for their plants.

    My apologies for the long-winded response - hope this helps ...
    All the best,
    Ron
    You must do the thing you think you cannot do. --- Eleanor Roosevelt

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    As Ron has said above, there is no simple yes or no answer. Perhaps one way forward is to try it for a season on some plants that you could afford to potentially sacrifice. I know from past experience that the conductivity levels can vary quite considerably here. I live about 30 miles away from Aberdeen, which is known as the granite city. As the area is primarily made up of granite the water is very soft and conductivity is usually less than 100ppm; however, after heavy rainfall that level rises somewhat. I have concluded that this is possibly due to run-off from agricultural land, in fact the area was in the news last year for have high levels of metaldehyde (slug poison) in the water, which could only have come from such sources. So, you see, just because the water quality if good at one point in time, it does not necessarily mean it will be the next time you use it. Having said all that, being human, I am lazy by nature and whilst I would only have to walk a few metres to get to my ample store of RO water, the Cephalotus 'Big Boy' in my bathroom frequently (read always!) gets watered with tapwater because the sink tap is closer! That Celphalotus is putting out some lovely big pitchers at the moment... and no fear of slug damage

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