Water question - tap or distilled?

Hey all, quick question. I’m gonna start an autoflower in FFOF with added perlite. I’m new to PPM and I have a quick question about the water I use. My tap water is 225ppm, my distilled drinking water is 18ppm. Should I water with tap or distilled, or does it not matter? I’ll adjust ph before watering but I’m not really sure what I’m doing with ppm. Thanks so much

What’s the pH of your tap water after you set it out overnight/24hrs?

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Good question, I’ll let you know tomorrow

tap water ph is 8.3 after leaving it out overnight

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So you might want to pH down before watering; however, OF has been too acidic recently, so it might balance out. Maybe do a test cup and see how the runoff tests.

In the end, soil is pretty forgiving, but you want to get slightly acidic.

Edit: the ppm is also inconsequential for a water-only soil. Save some money and use tap water.


Great, thanks so much. Using tap water definitely saves me some time and money!


Hey @jordan1 I’m in a very similar situation. My tap water ppm is 180ish, and 8.5 ph after letting the chlorine evaporate. It I also used a water treatment I got from grow store. Letting water sit out will let the chlorine evaporate but if your water company adds chloramines to the water then You will also need to add a treatment. It sucks, but still better and cheaper than bottled distilled water. Also just wanted to point out to be careful with your young seedlings straight into FFOF. However some growers do it and have great success. But depending on your environment, strain, and quality of seeds/genetics. To be safe, I used FFOF on the bottom half of my pot and FFHF on top half of my pots. The happy frog is much gentler on the young seedlings/clones. I think my next grow I’m going to up the FFOF just a littlle. Do like 2/3rds on the bottom and only 1/3 of happy frog on top. One advantage of using entirely FFOF is you can make it little farther without feeding. I started feeding in week 9 but should of started week 8 but was waiting on shipment. Just some thoughts for ya, it’s your grow…do what you think,is best and most comfortable to you. Best of luck. Keep us updated. Stay safe and stay medicated :exploding_head:

Thanks so much, this is really helpful. If I don’t know what’s added to my tap water, would you recommend I add a treatment or just see how things go with the tap water as is (left to sit overnight)?

I had heard ffof can be a bit hot for young seedlings but I’m gonna give it a try anyway. Would prefer not to buy another expensive bag of soil, but if this seedling struggles certainly I’ll change up my process for the next plant.

Surprised to hear you can wait that long for nutrients. How did you determine when to start? Are you just watching the plant and knowing from experience or do you decide based on ppm?

take the ocean floor and scoop you a hand full out where you are going to put your seed and get you a small bag of seed starting potting soil at the home depot (it;s cheap) and fill the hole with that, also check out R O buddy on amazon for your watering

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and i don’t bother with adding any perlite

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Perfect, thanks. I have seed starting soil, so I’ll do that. I’m not interested in buying an RO system. That’s money and energy I can’t spend right now, so I’ll be working with what’s available to me here.

These look great!

You can contact your water provider for a water report at your residence. This will tell you all the trace elements and what treatments they add(chlorine, floride, etc.). What I was told is that a lot of water companies switched from chlorine to chloramines. Or you could just get some to be safe. I use very small amount. It’s like 5ml per 10 gallons. I never make up 10 gallons, so I got some pipettes so I can add small amount while only mixing up three or four gallons. As far as knowing when to feed. If you are doing straight FFOF, you should definitely be good until at least week 6. So in the first 6 weeks when you water, try not to water to very much runoff at all. You don’t want to wash away all your nutes in the soil. I’d say about week 7, or sooner if your plants start looking hungry. But at week 7ish, you will want to water until you get little runoff. Get you a PPM (TDS meter) and check your runoff. This is parts per millions of the total dissolved solids basically it’s a reading of how much nutrients are in the soil. Depending on the strain and what stage of life cycle, but once your ppm of your runoff is below 1000 you should probably think about feeding. Tag me, and ask me again down the road if you need help with that. Once you start feeding then you will want to also start watering to about 20% runof, unlike when u did first 6 weeks. Once you feed, you need to water to runoff to prevent salts building up. More on that when we cross that bridge if ya need help. Any other questions…I’d be glad to help,if I can.

And btw @jordan1 I would recommend talking with water company or getting the treatment anyways. They treat the water with that stuff to help kill bacterial in our drinking water. The thing is…it can’t distinguish between bad bacteria and good bacteria. If the water has chlorine or chloramines it will kill the beneficial bacterial and microbes in your soil.

One million thanks, this is all so specific in a very helpful way. And I will definitely treat the water, seems like an easy step that could help a ton. I found this water conditioner for fish tanks. I assume it’s all the same, but should I get something specifically for gardening?

@jordan1. I’m going to be honest with you. I am not 100 percent sure if that will work. However…I am a betting man. And I would have no problem betting that what you posted should work just fine. Mine was bought at a grow store, so I know it was specifically for what I’m using it for. Maybe someone here will chime in will more certainty, but it sure does look and sound like it does the same thing as what I use. If you have a grow store near you…I’d play if safe and try and get something there. It’s really not much. I think my bottle was $13. And as little as you use…it will last ya. If you don’t have a grow store, then what you posted will probably be fine. But then again…do you want to risk your plants health on a “probably”. lol.

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I’m in Los Angeles, I can definitely find a grow store nearby. I’ll make sure I get the right product. Good call, good guidance!