TweetMeasuring the pH of pure DI water is easy when you know what to expect. In theory, pure water should have a pH of 7. When you actually measure the pH, it will most likely fall between 5.5 and 7 due to its absorption of CO2 from the atmosphere. This natural occurrence forms carbonic acid [...]
Measuring the pH of pure DI water is easy when you know what to expect. In theory, pure water should have a pH of 7. When you actually measure the pH, it will most likely fall between 5.5 and 7 due to its absorption of CO2 from the atmosphere. This natural occurrence forms carbonic acid in the water, lowering the pH. Since DI water is pure, there is nothing to buffer it and stabilize the pH. Below are a few tips to increase the accuracy of your pH measurements.
Tips for accurate pH readings
- First and foremost, use a high quality ph meter and ensure that it is properly calibrated with pH buffer solution. Check the manufacturer’s recommendations for calibration. The Ultrameter II 6P and the Techpro II TPH1 are portable pH meters that are extremely accurate and easy to use.
- When using a portable pH meter, avoid cross-contamination by thoroughly rinsing with the DI water that you will be sampling. If a glass beaker or cup is to be used, rinse that as well.
- Use small samples and minimize exposure to air, as this will lower the pH value. Taking samples from an open-air drum or tank will typically give erroneous readings. Collect samples from a sample port if possible.
- If you have access to high-purity reagent grade KCl (Potassium Chloride) salts, then you can buffer the DI water to stabilize the pH. Adding a tiny amount to the pure DI water sample will increase the ionic strength and reduce the absorption of CO2 from the atmosphere. Be careful not to contaminate the KCl salts. Use proper tools/utensils to add the KCl salts
- If no salt is available and all you need is a quick check of your system, you can flow the water from a sample port into your portable pH meter to measure the pH values. This will take slightly longer to stabilize. Be sure to use an accurate, waterproof pH meter and hold it closely to the sample port.
- Changes in temperature can affect the pH. Use a pH meter that is temperature compensated to remedy this issue.
If you need pH buffer solution, you can find it here at an affordable price.
Tweet If you are a greenhouse grower then you are most likely familiar with the importance of proper water quality for your crops. Water quality can easily be determined by taking measurements periodically. It is important to use accurate and reliable equipment to perform the measurements. A wide selection of high quality conductivity testers and [...]
If you are a greenhouse grower then you are most likely familiar with the importance of proper water quality for your crops. Water quality can easily be determined by taking measurements periodically. It is important to use accurate and reliable equipment to perform the measurements. A wide selection of high quality conductivity testers and hydroponic pH testers can be found here at an affordable price.
To determine the suitability of water for irrigation you can easily take measurements of the Electrical Conductivity (EC) and the Sodium Adsorption Ratio (SAR). In general, the higher the EC and SAR, the less suitable the water is for irrigation. Irrigation using water with high sodium adsorption ratio may require soil amendments to prevent long-term damage to the soil.
SAR measurements are provided with laboratory analysis of the water. However, EC measurements can be made using a portable EC meter. The Myron L AG6/pH was specifically designed as a pH and conductivity tester for greenhouse crops.
As a rule of thumb, the water is considered borderline and its use can present problems if conductivity values are higher than 0.8 millisiemens/cm (mS) and SAR is over 4. If the conductivity measurement is below 0.8 mS and the SAR measurement is below 4, the water is suitable for greenhouse irrigation. Particular management practices should be used when water is outside the acceptable limits. This might include using a growing medium with excellent drainage, leaching with every watering and compensating the sodium with calcium and magnesium.
If galvanized steel is used throughout the greenhouse and water is reclaimed for irrigation, it is a good idea to check the amount of Zinc in the water and make nutrient correction accordingly.
Many greenhouses use drip irrigation systems, which are efficient and low maintenance, but nozzles can become clogged by hard water. Check for high levels of bicarbonates (above 100 ppm) in the water and neutralize with the appropriate acids.
There are many factors that affect water quality and greenhouse crop growth. Consult your fertilizer manufacturer for recommendations on proper nutrient levels.