How to Test The pH Of Water (Complete Guide)

Testing water pH

When hydroponic growers first begin running their systems, there is one aspect that is so very often overlooked. This is the importance of the pH level of the water and nutrient solution. If this isn’t around the ideal levels, it can have a dramatic impact on your plants. The most significant thing with a solution pH is it can go up as well as down rather than only in one direction.

If this wasn’t enough, some plants require different levels, so setting the pH to one level can cause harm so some plants if they’re fed from the same reservoir.

Here, we will take a look at all you need to know about the pH of water, how you can adequately test it, track it, and control it for the benefit of your plants.

Understanding a Hydroponics Systems pH Levels

An Introduction to pH

What is it, and why is it so crucial in hydroponics? The meaning for the term pH means Potential Hydrogen, and it is one of the most essential parts leading to healthy plant growth.

All types of water have a different pH level. Tap water to bottled water and water in your system will all vary. When we measure this, there is a scale which reads from 0 – 14, and zero being the most acidic while at the other end of the range, 14 is the most alkaline.

Neutral levels are found at number 7, and this like our body is the region which plants thrive best. With this being said, there are a few plants which prefer a pH level slightly outside the range we consider neutral.

When we look at what this means for our systems, the ideal or standard pH for plants to thrive is under a neutral level, roughly around 5.5 and 6.5. But, there are a few plants that like the other side of the scale and grow best in the region of 8.

When the pH level is correct, it allows plants to absorb all of the essential micro, and macronutrients they need through their root system. Additionally, it is in this ideal range when there are higher uptake levels of the all-important NPK (Nitrogen, Phosphorus, and Potassium) which maximizes plants growing ability.

Understanding the pH Levels of the Plants You are Growing

Plants which are grown in the soil, grow equally well in soils that have varying pH levels and will range from around 6 (slightly acidic) to 7 (neutral). In a hydroponic system in most cases, plants need pH levels which are a little under the recommended for soil.

Here is a list of ideal hydroponic pH levels for a range of plants:

PlantIdeal pH range
Asparagus6.0-8.0
Basil5.5-6.5
Broad bean6.0-6.5
Broccoli6.0-6.8
Brussel Sprouts6.5
Cabbage6.5-7.0
Carrots6.3
Cauliflower6.5-7.0
Celery6.5
Chilli Peppers5.5-6.5
Chives6.0-6.5
Cucumber5.5
Eggplant6.0
Leek6.5-7.0
Lettuce6.0-7.0
Parsley5.5-6.0
Pea6.0-7.5
Spinach6.0-7.5
Strawberries6.0
Thyme5.5-7.0
Tomato5.5-7.5
Zucchini6.0

This list is by no means extensive and these are indicative of the levels required.

Testing and Measuring the pH of your Hydroponic Nutrient Solution

If you are a new grower, you will need a daily check of your solution to check the pH levels. After a while, you will come to understand your system and how all of the nutrient concentrations and water type you are using will affect the levels.

Before heading off with testing methods, it is essential to know the effect that different water types can have on a hydroponic system, and why many growers decide to use reverse osmosis water rather than tap water.

EC levels are the amount of conductivity the nutrient solution can have, or in simple terms, the amount of electricity that can pass through the solution. EC is dictated by the salt levels that are in a solution. EC though doesn’t tell you what salts are in your mix, and hence the reason for growers using reverse osmosis water. They want a clean slate where to begin so there is no guessing.

Once they have this water, they can take their nutrient bottles, and will then know precisely what will be in their solution. A point to note here is, never purchase nutrients that don’t come with a guaranteed analysis, or they are from a highly reputable company. All too often cheap nutrients can cause more harm than good to your plants.

By using good water, the levels of pH will require less adjusting, and by doing so will give less shock to your plants. Now, you can either decide to use reverse osmosis water from the beginning, or you can adjust the EC levels and then focus on your pH levels.

Ways of Measuring pH Levels in Hydroponic Systems

There are three ways in which you can measure your pH levels in your system. Here is an overview of methods available.

Litmus Test Strips

The simplest way is by means of litmus paper strips. Litmus paper contains a dye which is sensitive to the liquid it is dipped into.

In this case, it would be a sample of your nutrient solution. Once you have this sample and you have dipped your strip, you wait until the color changes, and this is then compared to a chart which shows the pH level.

Although this method is the cheapest, it isn’t the most reliable. Some of the colors for the different levels are very close, and comparing a small squab can leave you guessing at which one it is. For some plants, this approximate measure of the difference in pH might not be significant, but for others it can leave your plant battling for survival!

For a quick means of testing, they are handy to keep close to your growing area, but shouldn’t be relied on.

Liquid pH Testing Kits for Hydroponics

This liquid pH testing kits cost slightly more than their litmus counterparts, but with this price increase, there is more accuracy. This form of testing is commonly found for people who have swimming pools, so the process has been well tested over the years.

The way you perform this test is to take a sample of your nutrient mix, and then place a few drops of sensitive dye into the container. After a short while, the color changes and is then compared to a chart representing the pH levels similar to the first method.

Like the first option, there are drawbacks and the most significant being the color shades can be hard to detect and interpret. Both these tests should be carried out in good lighting conditions so as not to affect reading the colors.

Testing Hydroponic pH Levels with an Electric Meter

The final option is the most expensive, but it does give exact results without growers misinterpreting the reading of a color chart. These electronic pH testing meters vary in design, size, and price. One of the most common varieties is a digital pH pen. Once this is placed in the sample of the nutrient mix, it will give a digital reading of the exact level.

Although these are precise in their readings, this can vary over time, and they do need calibrating on a regular basis. In some cases, this can be weekly. This might seem to be a little overkill for some growers, but when it can be the difference between healthy plants, and ones which are suffering from a nutrient lockout, it can be a chore worth doing.

What you Need for Calibrating a pH Pen

There are two forms of calibration for these pens. One is digital, and the second being ones which can be manually calibrated. We will run through calibration of both, and first off is the equipment you will need:

  • Your pH Pen
  • Calibration solutions: One at pH 4, pH 7 and pH 10
  • Distilled water
  • Small measuring cups
  • Gloves
  • A small screwdriver will be required if you have a manually calibrated pH Pen

Digital pH Pen Calibration

Many of the pens use similar methods for calibration, so these steps will more than likely suffice for whatever digital pen you have.

  1. While wearing gloves, pour a small amount of the calibration liquid into separate measuring cups (solution must be room temperature). Now you will have one for 4, 7 and the third for pH 10. This solution should be as fresh as possible, so when purchasing, refrain from thinking a large bottle is leading to a cost saving.
  2. Before commencing, ensure the pens probe is clean, (Refer to cleaning pH pen section).
  3. Check the pens instructions for performing the test on the pH 4 solution. Most pens have a guide marker where you should submerge the pen too, when it as at this level, gently swirl it in the solution.
  4. Rinse the probe with distilled water, and then test on the two higher pH solutions.
  5. Not all pens require a 3-step test, but the more calibration points, the more accurate your pen will be.

Calibrating a Manual pH Pen

Although it might sound harder to calibrate your pH device by using a screwdriver, the process is straightforward. The actual testing phase is exactly the same, and all you do with the screwdriver is adjust the dial to match up with the pH.

Again, the more often you perform this calibration, the more accurate the results you will obtain. For anyone with an average sized garden, a period of between 2 to 3 feeds should be okay for pen calibration.

Cleaning of a pH Pen

Before use and in between calibration tests, the probe on the device needs to be clean. For 15 minutes before you conduct your solution testing, the electrode needs to be soaked in a buffering solution. If you have none of this solution, refrain from using any other water, because even distilled can erode the glass membrane.

If your pens electrode has been allowed to dry, you must soak it in the storage solution or a cup of pH 7 buffer solution before performing your testing. If the pen has been in storage, gently shake it up and down to disperse any bubbles which may have formed.

Keeping the electrode clean is one way not to affect the operation of the device. You should never wipe the electrode because this can affect any static charge in the device. Gently blot the device and bulb with lint-free paper. You should also be sure to never touch the bulb with your fingers, if you don’t damage the device probe, you can leave behind a residue that will stop the device from giving accurate results.

Some devices need storing in a recommended storage solution. These can be purchased, and when the device is stored and cleaned as instructed, they will deliver fast and accurate results.

pH Levels of Different Hydroponic Systems

Now we have seen the equipment you can use to test your solution, and how you need to calibrate your device. We will take a look at how different systems can have different pH levels. NFT is straightforward because the solution is in direct contact with the roots.

If you have a media based system, the readings can be a little more intense. Two readings need to be taken, one from your reservoir, and the second from the runoff solution (the leachate). If you have large plants, then there will be a difference in this before and after scenario. When you come to adjust your solution, you need to base the adjustments to your reservoir based on the pH of the leachate solution. This adjustment is required because it will be the level of PH your plants will be experiencing rather than the pH which is in the reservoir.

Adjusting Hydroponic pH Levels

There are a few reasons why your pH levels will rise or fall, and luckily, it can be quite easy to fix them. One of the easiest ways to avoid any spikes or drops in levels is to make sure your nutrient solutions contain pH buffers.

Many of the nutrient suppliers will also offer solutions which can raise or lower pH levels as required. One of the most well-used is pH UP and pH Down from General Hydroponics. When using these, it is crucial to follow the recommended doses, and in relation to how close to the desired levels your solution is when you test.

If your pH levels swing too far in either direction, plants can suffer from the nutrient lockout, so it is vital to regularly test these levels until you have a better understanding. When it comes to making these adjustments, there are only a few steps involved:

  1. Depending on your reading – add 1-2 ml of pH Up or pH Down per gallon of water.
  2. Stir your solution and wait for 30-minutes before testing your solution a second time
  3. Repeat as necessary until you reach the desired range for your plants

Your pH levels will change when you add nutrients, so you should always test once these have been added to a fresh tank. Apart from that, it is advisable to check around the same time on each day. There are a couple of natural methods to adjust pH if you are out of any pH Up or pH Down. These are a short term fix and should only be used if it is absolutely necessary.

Citric acid or white vinegar can be used to lower pH, while baking soda can be used to raise your pH levels.

Maintaining pH Levels in Hydroponic Systems

To finish off, here is a quick recap of how you can maintain your pH levels:

  • Check levels on a daily basis until you understand your system. After this, and you gain experience, once or twice per week might be enough.
  • Use the best testing kit you can. Litmus strips are best used for quick periodic testing.
  • If you see your pH levels are between 5.8 – 6.5, don’t be tempted to adjust anything. This is ideal for the majority of plants.
  • If your solution is too high then lower it with pH Down (phosphoric acid).
  • If the level is too low, then raise it with pH UP (potassium hydroxide).
  • Don’t rush for a quick fix to your pH levels, too much too quickly will shock your plants.
  • Keep records of how much solution you add to your tank.

Depending on where you live and are using tap water, you might not require too much adjustment, but for hard water areas, the change can be more significant.

Overdosing with either of these pH adjusters or nutrients can be harmful to your plants. Additionally, if your solution levels drop in your tank, then the pH levels will be changing at the same time. Much can be said if you are topping your tank with water, again your levels will vary.

Understanding pH levels is one of the best skills any hydroponic grower should take the time to learn.

How to Prevent and Treat Root Rot in Hydroponics

Many problems face hydroponic growers at different stages, and one of the most common can go undetected for a while and can cause severe amounts of damage to plants.

Root rot is a disease that can affect every single grower, and the symptoms can lead us all to think it is a deficiency in another area. Plants can begin wilting or showing signs of nutrient burn, or they might die altogether. There are many reasons these symptoms can happen from lighting, pests nutrients or feeding cycles, but in the end, it is a case of root rot.

Once we gain some experience, and if our plants have suffered from root rot, it’s a thing we always know to look out for. But, if we are unaware of what to look for, there is no way we’ll know how to prevent it, and how we can treat root rot in our hydroponic systems.

What Causes Root Rot in Hydroponics?

Root rot can affect plants in different ways. This will depend on if they are a flowering type, or they are crops such as lettuce or herbs. You will see plants can have symptoms such as curling leaves in an upward or downward direction, plants have slow growth, or there is yellowing in the leaves.

One of the reasons that makes root rot hard to detect can be that, it might be affecting all of your plants at the same time. All plants can suffer from stunted growth at the same time, so it might appear there is another problem.

The primary cause for root rot is insufficient levels of oxygen reaching your plant’s root systems. This is more often found in Deep Water Culture systems or systems where roots are exposed to water for extended periods.

You can quickly see if there is a problem by lifting your tank lid and see if it smells funny, this is a clear sign you have root rot in your system. Next, you can look at your plant’s roots. Some roots can become tinted from the nutrients they are absorbing, but if they appear to be brown and slimy, then this is a clear sign root rot has already set in.

It might sound like a simple problem to overcome. Monitoring your water levels and making sure there is plenty of air won’t be enough, because at this stage, something else will most likely be occurring.

Mold and pathogens such as Pythium and Phytophthora are water molds which can attack plants when the conditions are right. Nutrient solutions which are too warm produce the ideal conditions for these molds to grow, and they will rapidly infect all your system.

The spores of Pythium and Phytophthora become immobilized and can survive for several months. They take up home in the dying roots and are dispersed via reused growing media, polluted water or a system which has become contaminated. Even other equipment or things you handle can be enough to reintroduce these spores back into a clean system.

Either during this stage, or the first stages of root rot, a coating of slime will form around the roots. This barrier is strong enough to prevent any oxygen from reaching the roots, and it is this that allows these pathogens to worm their way in and smother any part of the root system.

Treating Root Rot in a Hydroponics System

A lot of what you can do to treat root rot will be the same as what you can carry out for prevention. But, there are a couple of things you can do to immediately tackle the problem is there are only a few plants which are infected.

If plant leaves are showing signs of dead matter, all this should be removed and discarded away from your growing room. You can remove your plants and physically clean the root system. If you do this over a sink, you can remove anything that is dead or slimy from the roots.

The next stage is to soak the root bed in a sterilizing agent up to a maximum of 12 hours. One product which is ideal for this is Physan 20. It should be noted, this product doesn’t know the difference between bad bacteria or good bacteria. This can also be an excellent time to begin sterilizing any growing equipment you have.

The addition of root builders can also be beneficial in helping roots grow stronger. These are packed full of good bacteria and help to aerate your nutrient solution. Many growers also use this as an addition to their regular feeding schedule as a way to boost plant growth and claim impressive results.

One other type of compound which can be added are microbial inoculant mixtures, these also help with new growth in the rooting system, and also aid in the eradication of diseases. The bacteria in these lead to the breakdown of what is causing the root rot.

Both the root builders or the microbial inoculants can be added as a prevention rather than a cure. However, these methods should not be relied on as the overall way of preventing root rot, this will come down to many other factors which will need your attention.

If you are looking for a natural remedy for root rot rather than using any of the above chemicals. The following natural recipe was devised by Heisenberg, who is a member of the rollitup forum. The following methods help breed beneficial microbes in DWC systems.

The following recipe needs to be added after you have performed the previous root sterilization, and system clean with Physan 20. This formulation isn’t added directly to your nutrient solution but formulated as a tea, which you then add as required. To make this tea, you do need to purchase a few ingredients, some of which are discontinued so we will provide alternatives.

Hydroguard or any solution that contains the bacteria Bacillus genus can be used. Hydroguard has plenty of good reviews, but the Hydroguard solution requires use within six months of opening, so it is better to order the smallest bottle required.

Great White comes from the same company as the root builder specified above, it delivers explosive root growth and contains mycorrhizal fungus that is well suited for a variety of plants.

Ancient Forest consists of 100% pure forest humus and contains a high diversity of microorganisms. This can be replaced by any earthworm casting product, but this is produced by General Hydroponics who are well renowned for superior products.

Before proceeding with the formula, there was an edit to the post. Both the Hydroguard and the Great White solutions can be replaced by Mycogrow soluble as a cheaper alternative.

Heisenberg Natural Formula Steps (Edited)

  1. Add 2 gallons of non-chlorinated water to a clean bucket, and add two air stones. For this to be effective, you need as much air as possible.
  2. Now, add 15-30ml of Hydroguard and about 1/4 to 1/2 scoop of the Great White powder (these are approximate, just don’t go overboard).
  3. Take an old pair of stockings or pantyhose and place 2 handfuls of Ancient Forest (or EWC alternative) inside.
  4. Tie off and place over one of the air stones in the solution. You can also put one air stone inside the stocking to give more stimulation. This method is more straightforward than straining two gallons of tea if you add the Ancient Forest directly to the bucket.
  5. Add one tablespoon of molasses. This wakes the microbes and gives them something to eat. Never add molasses to your nutrient tank. The beneficial bacteria will die in the tank due to starvation, but you will be replacing these, so it is okay.
  6. Let your tea solution bubble for 48-hours at room temperature. You can use it after 24, but it is more effective at 48. If you are using EWC, the water will foam, this is normal.
  7. After 48 hours, you can store your tea in the refrigerator where it can stay fresh for up to 10 days. If it begins to go bad, you can smell a bad odor. If you smell anything like rotting or sweaty socks, throw it away and make a new batch. Your fresh tea can smell of earth or slightly mushroomy.
  8. To start, add 1 cup to your nutrient tank for every gallon of water.
  9. Add 1 cup to the tank at 3-day intervals.
  10. You can drizzle a little of the tea at the base of your plant stalks. This helps inoculate the root crown (plant dependent). The solution can become cloudy, but your roots will remain white and highly stimulated.

When you multiply microbes with this method, your products will last longer. Once you have ridden your roots of slime build-up from root rot, you can add 1 cup for every 10 gallons at one-week intervals to help prevent future outbreaks.

Prevention of Root Rot in Your Hydroponic Systems

As we can see from the above information, root rot is a culmination of different elements and organisms. Before looking at how we can prevent root rot in your systems, here is a quick recap of the factors which can lead to its appearance:

  • Dead or decaying matter in the reservoir – any dead leaves can start something terrible.
  • Lack of oxygen – Once water becomes stationary, it becomes stagnant, and there is no oxygen passing to your roots.
  • Heat – Warm nutrient solutions make it easy for bacteria to reproduce. A cool reservoir makes it harder for bacteria and fungi to survive.
  • Agitating young roots: When roots are young, they need a chance to build up their defenses. Moving them will weaken these and expose them to pathogens that can quickly attack.
  • Light leaking into the reservoir – This can be a boost to any unwanted growths.

Solutions to Prevent Root Rot

To not only get rid of but to also prevent root rot, you need to take a two-pronged approach. This includes:

  1. Directly treating the plant’s roots – same as above in treating against root rot.
  2. Changing your plant’s environment – changing how plants are growing, so root rot is unable to.

Some of the following procedures will be the same as the treatment steps above but are crucial steps nonetheless.

Adding Beneficial Root Bacteria

As prevention, these beneficial bacteria can be added throughout your plant’s growth. Once mixed with the water, they are a handy way of preventing and treating root-related diseases while making sure nutrients are available to your plants. Subculture B, Rooters and Piranha being alternatives to the preferred formula Hydroguard.

The one bacteria that is most beneficial is Bacillus Amyloliquefaciens because it will survive better in reservoirs than other forms of Bacillus bacteria while fighting a vast number of root ailments.

Plenty of Bubbles

Because lack of oxygen in your system is the primary cause of root rot, it is essential to make sure you have plenty of bubbles. If everything appears to be okay in your system, and you are still showing symptoms, it might mean you need a secondary air pump, or a larger unit altogether.

Root rot can’t thrive in an oxygenated environment, but, it is also crucial to make sure your roots are not being overly disturbed. You can never have too much oxygen in your water, so finding the ideal position for your pump will bring nothing but benefits. You can find some air pumps with dual outlets. These can either be placed in separate tanks or different locations to maintain healthy air flow.

One pro tip is to make sure your hoses are black so no light can penetrate.

A Cool Grow Room

It is essential your growing area is under 80F with the ideal being under 75F if possible. This is the easiest way you can lower your reservoir temperature without the use of a chiller unit. The warmer solutions become, the less dissolved oxygen they can retain, and then can’t pass the highest oxygen amounts to your plants.

Using one of the supplements mentioned, you can let you run your system a few degrees warmer, but it is far better to try and maintain around the optimal 72F for your water.

Being Clean and Sterile

Any dead leaves or debris that find their way into your reservoir will become a breeding ground for bacteria. Cleanliness extends way beyond your reservoir and includes all of your growing areas. One bit of advice is to thoroughly clean all of your growing tools either in between growing periods or on a routine basis. Hydrogen peroxide only delivers a temporary solution. Anything stronger and you need to make sure it doesn’t find its way to your system.

When you have a regular cleaning routine, this goes a long way to letting any pathogens survive in your growing area and hydroponic system.

Stop Disturbing Roots

With the way a hydroponic system works, it is essential for you to change your water on a regular basis. When you do this, you can disturb the rooting systems. In the later stages of plant growth (flowering stage), these become sensitive to pH and nutrients. Changing water between one week and ten days helps plants access nutrients easier.

What is crucial is do not disturb plants when they are seedlings or clones and are trying to become established in your system. At this stage, they lack a colony of beneficial bacteria and have not developed their own biofilm which helps protect their roots against pathogens.

If you are in need of changing a full reservoir, this can severely upset the balance, and young roots might find they have to start again from scratch.

During the first few weeks of a plants growth (plant dependent), it is advisable to only top the reservoir up with additional nutrient water before making a full change and system flush. It is, for this reason, it is a continual struggle against root rot.

Prevent Light Entering Your Reservoir

As much as harmful bacteria and organisms love the light, roots hate it in equal amounts (think air pruning). If you are using grow lights, this problem is worsened because you are giving everything these bacteria need to thrive.

DWC reservoirs are kept in almost pitch black by a lot of hydroponic growers. To be sure you have a reservoir which is capable of fending off any light, there are a few things you can do to help.

  • Use black tubing – This stops light leaks which might not be obvious.
  • Reflective coverings – Your reservoir lid could be getting warm from your grow lights if it is dark in color. However, using a reflective material can prevent heat seeping through the cover and warming your reservoir interior.
  • Reservoir construction – there are many reservoirs which have a thin wall construction. The thicker you can get the better because these are less likely to let any light soak through.
  • Taping light leaks – light can get in all sorts of cracks and gaps. Be sure to tape these with thick tape that will prevent light seepage.
  • Net pot light seepage – you can cover the tops of net pots to prevent light soaking through the growing media. Net pot covers are a quick and easy way to avoid this.
  • Black tubing – dark tubes can prevent light exposure to your reservoir. This often goes unnoticed.

Conclusion

There are plenty of hydroponic growers who throw in the towel if they find out they have root rot, and get rid of all their plants and start again. However, not all occasions require anything this drastic, and the same problem can occur if there are no preventative measures in place.

It can be more beneficial to get root rot and save your plants, because this way, you will know the symptoms, and best of all, you will know how to tackle the problems. There will be occasions when you can’t save your plants, but when you know there is something you can do, it will reduce the chances of losing any crops at a later date.