adjusting ppm's for tap water
- Thread starter asdfkry
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Tyrannabudz
Well-Known Member
Assuming you know the NPK content of tap water. Which it is most likely to have only calcium, magnesium, iron. There are a myriad of other trace elements in tap water as well but none of them are actual plant nutrients in relation to NPK. Just know that you should not need to add any Cal/Mag supplements to your nute regiment because these elements are already in your tap water. You may even end up with a Cal/Mag toxicity, depending on the mineral content of your municipal water.
The water in my area is heavily laden with calcium and magnesium. To avoid toxicity I alternate tap water, and water I harvest from my dehumidifier. When that runs low I just use distilled water as an alternate. Good luck hope this helps.
The water in my area is heavily laden with calcium and magnesium. To avoid toxicity I alternate tap water, and water I harvest from my dehumidifier. When that runs low I just use distilled water as an alternate. Good luck hope this helps.
homebrewer
Well-Known Member
Just because you're using tap water doesn't mean you don't need calmag. Get a water report from the city as that will tell you exactly how much calcium, magnesium, sulfate, chloride, and sodium is in your water. It may turn out that you have 90ppm of calcium alone and excessive magnesium or calcium will lock out each other. Having too much of both is better than having too much of just one.
But to answer your question, if your base is 100ppm and you want 1000ppm, then you need to add 900ppm of fertilizer. At 100ppm, it's pretty safe to say that you're going to need a fertilizer with ALL six macro elements present in good ratios which is nitrogen, phosphorus, potassium, sulfur, magnesium and calcium. 100ppm tap water is generally always desirable.
But to answer your question, if your base is 100ppm and you want 1000ppm, then you need to add 900ppm of fertilizer. At 100ppm, it's pretty safe to say that you're going to need a fertilizer with ALL six macro elements present in good ratios which is nitrogen, phosphorus, potassium, sulfur, magnesium and calcium. 100ppm tap water is generally always desirable.
rosecitypapa
Active Member
What is the good ratio of sulfur to the other elements?
homebrewer
Well-Known Member
I see 1-2% sulfur content to be a pretty standard amount.
xivex
Active Member
Hey my $0.02... Check your tap often as it can easily change from season to season depending on various factors! So while a city water report is a great starting point, it may be totally different compisition in 6 months from now. Just something to keep in mnd. Watch it and check it often.
rosecitypapa
Active Member
So for N,P,K,C,Mg,S
The ratios would be 3 - 1 - 2 - 2.4 - 1.2 - 1.5 ?
Whereas,
Calcium to Nitrogen is .8 to 1
Magnesium to Calcium is 1 to 2
Sulfur at 1-2% of total solution
homebrewer
Well-Known Member
The secondary macro elements as well as the micro nutrients more or less just need to be present in good ratios to one another and shouldn't necessarily be looked at in ratios to the NPK content. 3-1-2 is good for veg, I've noticed a 2:1 calcium to magnesium ratio among many products and 1-2% sulfur is pretty common. Micro nutes should be available in their trace amounts and though plant nutrition is a balancing act of sorts, as long as you're not excessive on any one element, your plants should be able to do what they do and pull up what they need.
