Just a simple quick question for anyone to answer that knows.
Tap or Pure Water?
Does it make a difference, is it worth it?
With RO water you know exactly what you are feeding. Many use tap water and adjust how much they feed based on what is in the water…but it requires that you know what is in your water.
Tap water source but I have decent water quality. Check your water source TDS or pull the latest municipal water quality report Grow Bro 
In most cases, tap water is fine. In most cases, it doesn’t make a difference, so no, it isn’t worth it.
If your tap water TDS is reading four or five hundred ppm for example, and you want to feed at 900, then you are only adding 400 of the nutrients as opposed to if you use RO water with the TDS testing at 100 or less then you are able to add more nutrients to your feed.
So let me ask this, I use my tap water it is about 200 PPM. But I never really subtract my taps PPM from my feed, is it really that necessary? For example like right now I fed last night at 1500 PPM and I don’t notice any problems I’m just wondering
You don’t subtract the PPM of your tap water to your feed you actually add it it becomes the first value of your total feed
I got you but what I’m asking is, if the target feed is 1,000 PPM and I mix it at 1200 PPM you know with my tap water included is that really a problem? is that really a problem?
I could write a novel here but I’ll refrain as much as possible.
My quick answer would be if your water source is high PPMs, start with your nutes as directed and watch your ladies. If they begin to nute burn, you could back off on the nutes some or change water source. Or if you start seeing a def/tox, you could adjust accordingly.
This has been a question in my head for a while now and I’m trying to work it all out. I’ve read where the balance of nutes in the medium is important and an imbalance can cause deficiencies or toxicities. So, I would think the breakdown of the PPM of your water source is important to know. I’m using my well water and I haven’t gone as far as getting the breakdown tested yet.
My well water comes out at about 150 PPM and pH at 4.7 - 5.0. The first two grow with salt nutes, I wondered if I should be accounting for them in the final feeding, wasn’t sure, so I did to avoid nute burn. But switched to organic dry nutrients since and the 150 PPM is not my concern now, it’s the 850 PPM of my water after adding a touch of calmag and a pH up product called Earth Juice crystals, that’s all. And the crystals is listed as 0-0-47 but that’s the relative ratio in of the crystals in the bottle, not the ratio once mixed into the soil. Baking soda works just as well to bring the pH up but it raises the PPM just as high and I’ve read where it may build up in the soil.
But I’m working with what I have. Trying not to overwork myself or spend a bunch of money for water. Now why can’t I give a nice, short & sweet answer like that @Lostgirl 
I started out using RO exclusively from a local dispenser - 5 gallons is $2.50. I got tired of that and started using tap water. my tap water comes in at around 220 ppms with a PH right at 7. However, when I mix nutes (Jacks 321 and CalMag), the PH comes down to 6.4. I haven’t looked back.
That’s not fair! 
Ditto. My tap is 7-7.5 pH and 400-450 ppm, and Jack’s brings pH down to mid-6s, which I take farther down to 5.8 (coco/hydro requirement).
But why the CalMag? Jack’s has plenty of both elements already - magnesium in part A and Epsom, calcium in part B.
When I lived in Cali my muni water was 550 ppm at the tap. This is WAY too high to not have to correct for. I had to get an R/O system so I had more control. Where I am now my base water is 135 ppm so didn’t feel it necessary.
If your plants tolerate the higher TDS then great. However; you may grow a plant that’s a bit more…discerning haha than others which means you’ll have to adjust accordingly.
When you’re talking 200 PPM differential I would say it’s not a big problem. If you go over that it could potentially start turning into an overfeeding. I’m assuming you’re tap water somewhere around 200 PPM
If it were me, if I had 200 PPM and my target was 1000 I would simply add 800 PPM of nutrients allowing me to stay at my 1000 PPM Target.
Like I said, 200 PPM isn’t going to matter one way or another in my opinion
@Lostgirl okay so where do people get their target number from? I just follow my schedule for CX horticulture nutrients and with me listening to my schedule sometimes after mixing the nutrients my PPM comes to 2000! I’m guessing the target PPM has to do with wood stage of growth it is in I assume. I mostly hear people talking about targeting 1,000 PPM, what if your nutrient schedule ends up being more
They’re often included in the nute vendor feed charts.
LOL I dunno why I’m still using it A couple grows back I had a deficiency and used CalMag and it helped. Current plant showed similar symptoms and I picked it up again. I use 3ml per gallon. Maybe I don’t need it but it is not hurting the plant. I’m sure I could stop using it but karma and jinx and all that stuff.
@Deadhead okay so 1,000 PPM is like an average Target or something? Cuz that is what I mostly hear people saying there targeting 1,000 PPM but I guess all circumstances are different huh? If I’m following my chart and come out with 2,000 PPM then that means 2,000 PPM is my target right? right?
Nutrient suppliers are in the business of selling nutes. So a higher number means more to buy.
That makes sense