Thread: Soil Runoff pH, Flushing to correct lockouts- Why and how to do it!

This is a common question that comes up when troubleshooting, so I thought I'd post up a little summin summin.

Why do you want to know your runoff pH? Simple- it's an indication of how your water, fertilizer, and grow medium are interacting chemically.

There are 3 measurements that are important to know when you are caring for plants growing in a soil or soilless medium.
The first is the pH of your source water.
Next is the pH of your nutrient solution after the fertilizers and supplements are added.
Last is the pH of your soil. But that's the hard one! You can't just stick a pH meter in the dirt and get an accurate reading, and the cheap metal-probed meters that show this are usually not all that precise.

So how does one determine soil pH accurately? With a runoff test! First, measure the pH of your tap water and record it. As an example, let's say that it is 7.0, exactly neutral.

Now place the pot over a clean rinsed container and pour enough water through the soil to start dripping out the bottom. Collect about 4 ounces of runoff water. Check to see if it is discolored as well.

Now, if you only have liquid indicator, which is just fine, pour this water into a clean small tube or the test vial that came with your pH testing kit.Add a few drops of indicator solution, shake, and read the color change.
If you have a meter, simply stick the electrode in the water and read.

Let's say that your runoff comes out at 6.5. How did that happen? The water passed through a more acidic matrix and dropped its pH. You can assume that your true soil pH is a couple tenths of a pH point lower than the runoff in this case- I'd assume about a 6.2. If it comes out HIGHER, just go in the opposite direction. If it came out 7.5, you can assume that you need to drop down from about 7.8.

You want around 6.0-6.5 for a soilless mix, or 6.3-6.8 for soil.

Pics:
1- Propping up the plant over a container to catch runoff
2- POuring clean water through the soil
3- For liquid indicator, pour into clean vials
4- Check the pH against the color chart
5- Adjust the flush water if necessary

May I add something here? Well too bad......I'm going to anyway. I was talking to my hydro man and he told me about check PPMS of soil runoff........particularly valuable when flushing a plant or deciding whether or not a plant may need to BE flushed. Know anything about this Stinkster?

Oh yeah, I forgot that. When I said see if the liquid is discolored, that's another indication that you might need to flush. You SHOULD measure ppms in a soilless mix, but usually if the pH is correct and you see lockout/scorch symptoms, you can tell that you need to flush. Most soil growers don't have EC meters. I've TASTED my runoff before to determine salt buildup- it definitely has a flavor all its own- salty, yet metallic! A fine vintage!

wouldn't the fine particles of soil, etc., in the water throw off an attempt at a ppm measurement ? ...

Originally Posted by the image reaper

wouldn't the fine particles of soil, etc., in the water throw off an attempt at a ppm measurement ? ...

I'm going to say yes to that. Solids suspended in the water might not agree with your meter- if you want to test EC, I'd run it through a coffee filter first. But again, if it's soil, it's not really a big deal.

I'm merely a parrot here........my hydro guy says you can check runoff and determine IF you need to flush by the numbers (he says he usually will flush with a number around 900ppm) and then AFTER flushing he likes the ppms around 300 so Reaper you don't try to be as exact with it as with hydro. My understanding of this is that its much more for overnuting than ph in this case........but he SWEARS by it.

I agree Stink.....most soil growers DONT have e.c. meters to measure that stuff with. And while YOUR eagle eye (and eagle tongue ) may be able to see when something needs flushing etc....NEWB soil growers like me need all the help we can get.

Was it Hanna pH meters that have been getting questionable reviews? I found a Hanna pH/TDS/EC meter the other day on Craigslist for like $50, but I didn't call the guy because I thought I heard some bad reviews on Hanna products. Did I goof? Now that I've looked at some similar products online, it seems like it would have been a bargain, at least price-wise.

I'm trying to amass some toys for my trip into the world of hydro, but I have no idea what's reliable and what's not...

so...if i'm using distilled water with a ph of 7 and add 1 tsp/gal of cal/mg which brings my ph down to 6ish (silly fish tank chemical ph tester is hard to tell exactly where its at) and my runoff measures at 6.5ish is the ph too low?

I'm not a fan of Hanna, and my local hydro shop doesn't even stock them (the Oakton pH and Truncheon EC are apparently the best bang for your growroom buck as far as they are concerned).

6.5 is not too low for soil or soilless, but definitely keep an eye on it in case it gets any lower. I'm surprised that your distilled water measures at 7.0- generally, the presence of dissolved atmospheric gases (sepcifically CO2 and N2) will actually drop 'pure' water down into the 6's. You might want to get a 'second opinion' on your test kit!

Remember, for soil grows, tap water is perfectly acceptable in most cases!

Add an airstone to your bucket that you let water sit out in, and consider a fish tank filter that accepts loose activated charcoal to run that water through recirculating for a couple days to reduce chloramine levels.

I found this about chloramine removal at home, and the rest of the article is a good explanation of the chemical and its use:

Drinking Water: Chloramines Water Disinfection in Omaha Metropolitan Utilities District , NF02-505

Chloramine Removal
Many water treatment techniques and equipment are used to alter and improve the quality of water. Several commonly used ones are not effective in removing chloramines. Worth noting are reverse osmosis and water softening units, neither of which effectively remove chloramines. In addition, boiling water does not effectively remove chloramines. And, unlike chlorine which dissipates when water sits for a few days, chloramines may take weeks to disappear. While sunlight and aeration help remove chloramines from water, allowing water to sit is not a reliable method of chloramine removal.
Two effective methods for removing chloramines include using a chemical to neutralize chloramine or using a granular activated carbon filter. Most pet stores sell chemicals for dechloraminating water and can provide use recommendations. Remember that chemicals that remove only chlorine will not remove chloramines. When using a carbon filter, ensure that it contains high quality granular activated carbon. Carbon filters should be operated at a slow rate to allow sufficient contact time for effective chloramine removal. Testing the treated water will help determine the optimum filtration rate. Filters must be monitored carefully to determine when the carbon media has reached the end of its useful life and needs to be changed. Manufacturers often indicate the maximum number of gallons that can be filtered before the filter is renewed. Check with the supplier for proper operation of equipment for chloramine removal.
A carbon filter also will remove chlorine, hydrogen sulfide, organics, THMs, some pesticides, and radon if present in the water. Unserviced or improperly serviced equipment may deliver surges of water with high levels of some of these contaminants. As the owner or user of a home water treatment device, it is your responsibility to ensure proper operation through monitoring, maintenance, and service.

I love my well water...7.3 going in....6.7 coming out.......(ok ..ok...it's not the prettiest female plant around)...but she's alot of fun to be with...

holes drilled in the table and the pot...drains completely in 20 minutes, into the bucket.

AWESOME. Very clever flush setup. Plants are SUPPOSED to look scruffy right before harvest but you'd never know it from the pics in the magazines. A ripe cannabis plant is ANYTHING but photogenic.

Use your commercial PLANT pH up/down- not the kind for pools- ad add it dropwise until the fertilizer solution is at the correct pH for your grow style.
The ideal 'middle' of each range is given here:
Hydro 5.9
Soilless 6.4
Soil 6.7
If you find your soil, for example, is giving a runoff that is too low, water with fert solution that is lightly HIGH- around 7.2- until you see that the runoff is in the correct range. If the runoff is too HIGH (much less common), use ferts at 6.2 until it improves. It's easiest to do this as a flush- all in one shot.
Be careful of shocking the plants with water that is more than a full pH point off their ideal range, even as a flush solution.

hey stinky
I was wondering what household and/or organic materials can be used too safely raise and lower ph. I have heard baking soda too raise it.someone told me vinegar to lower it. are these correct and do they work without harm?
are there other things that work. ty

ps: I have been searching the forums for threads on water.
I haven't found any yet. my tap water comes out very green in test.
also guy at hydro shop said chemicals in tap water will kill micronutrients like earthjuice micronutrients.my available water sources are: tap water/bottle water/distilled water/ reverse osmosis water/ creek water. which would you recomend I use? I am thinking I should use the creek water, could I run into unforseen problems from the creek water, it does run pretty fast so its not stagnent water. thx for any light you can cast on these subjects

Wow you are basically asking about water chemistry so this is going to be a long post, or several posts lol because I doubt I'll be able to get to it all at once!

Okay, first the easy one, which is household pH up/down products:
To lower pH in an emergency, the easiest and safest products are cider vinegar and natural lemon juice; acetic and citric acids, respectively. Now, these are ORGANIC rather than INORGANIC acids, and are also in the family of WEAK acids- they have a complex chemistry compared to the STRONG acids, and go into an interesting buffering equilibrium in your solution. Preferably, you would want to use a strong acid such as Phosphoric or Nitric to lower your pH- the H+ ion dissociates completely and acts to 'cleanly' lower the pH of your solution by acting on OH- ions that are present, and combining to form water, and a salt (from the N or P combining with whatever the OH had originally been attached to). This is a really oversimplified version lol.

To RAISE pH, you actually would want to avoid baking soda, which is chemically Sodium bicarbonate, and plants have a very low tolerance for sodium, so by the time you have raised your pH, you are already at a potentially harmful concentration of Sodium in your solution. Limestone is Calcium carbonate, and lime is a much safer additive. I have not actually tried this, but if your tap water is very acidic, you should be able to put some lime in it and shake it or stir it to try to neutralize some of that acid and raise the pH, but I'd let it settle after and pour off the liquid and discard anything that has fallen out of solution or suspension. Or get some pH Up...
The trick is to start with a soil mix that contains a natural buffer or pH balancer. Lime in your soil is one type of additive; others are -oddly- organic acids! Back to the buffering qualities of organic acids; there are some that buffer close to neutral, which functionally acting as an acid still. A common example of this is Humic acid, which you will find in the mineral Leonardite, in composted leaf litter (humus), and in many good fertilizers and additives like Pure Blend, Canna Bio, TopMax, Soil Syrup, and many many others.

Okay next subject: Your tap water 'killing micronutrients'. Well, if that was the exact wording he used, he is sadly underinformed in this area. Micronutrients are by definition trace amounts of metals that your plants need- at very low levels!- such as Boron, Magnesium, Zinc, and others. They are inorganic and cannot be killed. They will often be added to fertilizer as their Phosphate salt if it is soluble (the format being for example Magnesium phosphate), or chelated by an ion such as Oxalate or EDTA. Chelation means making the metal unable to interact with other things in your solution and become harmful to your soil environment. Chelators are important components of 'flsuhing' or 'clearing' solutions. Humic acid, among its other cool properties, is a valuable chelator! I have been known to flush my plants with a very weak solution of Humic acid.

Back to what Hydro Shop Guy is on about... Tap water contains chloramine, which will kill bacteria if the concentration is high enough. This could be an issue for you if you are running a pure-organic grow that depends heavily upon a living soil with bacteria, fungi, and other microorganisms in it, breaking down your organic fertilizers into components that the plants can actually use. If you have a highly treated tap water, organic growing may be difficult for you. Chloramine may be removed with activated carbon- you can set up a 5 gallon pail with a fish tank filter of the sort that has the hand-packed charcoal chamber, and let it run overnight to drastically reduce the concentration of contaminants in there. I don't know how much water can be treated by a specific amount of carbon, and it depends also on particle size of the charcoal and concentration of chloramine in your water.

Water sources pros and cons:
Tap- 'Tap water' is a pretty broad term and can mean anything. I'll assume you mean 'city water'. It's usually at an acceptable pH and hardness, but may be TOO hard and sometimes has high levels of disinfectants in it. It may be difficult to use for hydroponics, especially if it is 'hard'. Check your sink for evidence of 'lime scale' for a quick diagnosis that yup, it's way too hard.
Bottle water- Bottled drinking water often has too much sodium in it, and it's expensive. Not my choice.
Distilled water from any source- Actually a pretty good choice, and if your AC or dehumidifier has a plastic, not metal, receptacle, you might even be able to use that as distilled water (depends on the condition of the coils and if they are leaching off metals into the water as they condense it). Distilled water is predictable. You have to add calmag plus to it, up to ~200-300 ppm, and then check the pH. It should come out correct after addition of your calmag.
RO/reverse osmosis- Great stuff, better quality than distilled, more predictable even; again you have to add calmag.
Creek or stream water- Where does your stream come from? Look upstream. What is the landscape like? You can end up with serious issues. I'd avoid it in general; it's just too unpredictable, and subject to rapid changes with weather events or upstream releases.
Well water- Again, it depends on where your well is located. I had SERIOUS problems at a location where the well water was loaded with organic acids, and even though it tested a perfect 7.0, it used up all the lime in my soil in like 3 weeks and killed a crop. lol. Gotta love how Nature outwits us no matter how smart we think we are!

A final note on pH, ionic strength, and calmag.
RO water has an ionic strength, theoretically, that approaches ZERO. Any pH readings on pure RO or distilled water mean NOTHING! Unless you have a research-grade pH meter (you don't, I promise!) that can actually read solutions where the conductivity is close to zero, don't even bother! Read your pH AFTER you add the calmag and create your perfect 'imitation tap water'.
Most pH meters we all have are designed to read HIGH ionic strength solutions. This means at the fertilizer or waste water level. Imagine you are looking at a city from high up in the air. You can barely make out individual people walking around. Now imaging that all the people are standing close together in a crowd. Now you can see that there are actually people there! That's sort of the idea. Your average pH mater can only see and measure the crowd.

Okay that's enough of that for now. I have to go play with Phosphate buffers and dialyze some proteins!

I did not see this mentioned specifically but I may have missed it......also do not use ph ADJUSTING products for fish or aquariums. As Stinky said....stick with ph up and down for plant use.

PH TESTING products for aquariums are ok although some don't offer a large enough range to be helpful.

Thank you all so much for my ejumacation!!! I feel like I need to put my tithe in the hat!!! I have read this before and it makes more sense each time! Getting closer to my grow!!! this is a great thread!

You all must have PhD's in growing! pr

Originally Posted by painretreat

You all must have PhD's in growing!

Pot Head Degree?

I've been watering my plants with tap water. I never had a ph meter and the plants did fine. I recently purchased the ph tester drops and fed the plants once with what was appearantly too low ph'd water.

The plants' leaves began showing brown spots. I'm sure it was because of the low ph. Anyway.....can I just water again with my plain tap water like I was before to correct the problem? It was only 1 watering of the low ph'd water.

Originally Posted by stinkyattic

Use your commercial PLANT pH up/down- not the kind for pools- ad add it dropwise until the fertilizer solution is at the correct pH for your grow style.
The ideal 'middle' of each range is given here:
Hydro 5.9
Soilless 6.4
Soil 6.7
If you find your soil, for example, is giving a runoff that is too low, water with fert solution that is lightly HIGH- around 7.2- until you see that the runoff is in the correct range. If the runoff is too HIGH (much less common), use ferts at 6.2 until it improves. It's easiest to do this as a flush- all in one shot.
Be careful of shocking the plants with water that is more than a full pH point off their ideal range, even as a flush solution.

Whats the difference between hydro & Soilless?
Sorry for the newbie question.. Just im using a halo system in hydroton and i believe this is 'hydro' and 'soilless' so am slightly confused..

Yo Stinky I have a ? if you dont mind. I have 2 plants outdoor. Both of which are Indicas. 1 gets about 12.5 hours of light. Other gets 13.5 hours.They're buried in about a 2.5 ft deep X 2 ft sq hole. I used 75% miracle grow soil, 10% moisture control soil, and 15% reg dirt. I use well water which test perfect. Jamacian guano as fertilizer once a week. I have been using superthrive the past 2 weeks. Once a week as well. I have done it like this for 5 years now. an 4 days ago they both started wilting. Lower leaves have turned yellow, some of which have browning on the tips. I have watered them to make sure thats not the problem. There is no major bug problem. Do you have idea what else might cause me these problems?

hey bud, stinky hasn't been around for abit check IC mag com for stinky ..
or fill out that plant problems checklist and another fine grower will try to help ya out, have you feed too much nutes & locked em out? or the biggest easiest mistake with babies is overwatering,, maybe there just hungry! I cant tell