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The abbreviations PPM confuse many marijuana growers. In fact, most are ignorant about it altogether. PPM means Parts Per Million. When used in marijuana farming, it refers to the concentration of minerals in the water given to your plants. It is important to know the amount of minerals in the water so as to give the required ratios to our plants. 1 part per million is equal to 1 mg of solubles per litre of water. Most of the times, tap water will be between 200 ppm and 400 ppm. We are going to demystify ppm, TDS meter, EC meter and how they assist in marijuana growing.

TDS meter

To measure the ppm of water a marijuana grower will use a TDS meter. It is a perfect tool for measuring the ppm and a credible grower ought to have one. There exists a wide range of TDS meters in the market. Some even measure temperature. It will narrow down to your budget. In marijuana growing, the ppm levels will not exceed 3500ppm. For indoor plants, the ppm level will be around 1500 ppm.

EC meter

An EC meter is a tool to measure the amount of electoral conductivity in water. In marijuana farming, TDS and EC meters are almost the same. The reading in the EC meter comes in handy in knowing the range of solubles available in water. This is the same as in TDS. However, for the purposes of distinction, electrical conductivity is measured in s/m (Siemens per meter).

One can convert s/m into ppm. We can, therefore, see that these two tools are very much related. It is advisable to use the TDS meter over the EC meter to avoid complications. This is especially because many feeding charts for our plants will be written in terms of ppm. Therefore, if you are using an EC meter, you might be pissed off trying to convert figures.

Importance of these meters

We have come to a conclusion that the TDS meter is the simplest and yet efficient one to use. Using it will help you prevent issues of overfeeding your plants. Sometimes you will find that your plants will ever get burnt by nutrients even after reducing the nutrient level. This might be as a result of variations in the mineral concentration in the water. What you need to do is to get a TDS meter, buy a calibration liquid which ensures the meter gives correct readings and you will be good to go.

The process is a simple one as it involves putting the electrode of the meter in the water to be tested. After 2-3 minutes, you should be able to make a reading.

Values at different stages of growth

We are going to have an estimate of what you will expect during the entire growth process of the marijuana plants. When measuring the ppm pH level.

During transplantation marijuana seedlings, the measure will/should be between 500-600ppm. At the vegetative phase, the reading will be around 800-900ppm. During the period where the pants move from the vegetative phase to the flowering phase, the concentration will be between 1000 and 1100 ppm. The level lowers during the pre-harvest to harvesting. At this stage, it is usually between 400-500ppm.

pH meter

A pH meter for the soil would be ideal to use alongside the TDS/EC meters. This is because sometimes the soil nutrient concentration may be high or low. It will a=directly affect the plants’ growth. The best pH level for growing marijuana plants is around 6.5. Corrections for the soil pH can be done using phosphoric acid and potassium hydroxide.


The concept of pH measuring in water and soil in marijuana growing is widely ignored by most growers. However, it is these small details that make a difference. They could cost you a lot if not taken care of. It would be advisable to seal any possible loophole since our sole aim is to have healthy plants.