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What should the E.C and pH be of my grow room drainage water from a run to waste system?

Generally, you would want the output E.C to be about 0.1 - 0.5 (200ppm/3Cf) higher than the input E.C.

For example, if your input conductivity is E.C 2.0 then the water draining from the pot should be around 2.1-2.5 E.C is higher than the input by > 0.5 higher you will need longer irrigation times, if the output E.C is the same or lower than the input E.C then shorten the irrigation times. These rules only really apply as the plants gets bigger (maybe 3-4 weeks old) and start to use significant amounts of nutrients and water.

Note that with smaller plants the drainage will tend to have conductivity similar to the input. With the pH, try to maintain the average between 5.5 and 6.5. For example, if your output pH is 6.0 and the input is 5.8 then the average is 5.9. You will have to adjust your input pH in order to get the desired output if your pH is outside the desired range.

What should the pH of the nutrient solution be?

Ideally, the pH should be maintained at 6.0 as at this point, a drift of half a pH point down to 5.5 or up to 6.5 is entirely acceptable for your grow room.

It will fluctuate, so maintaining the pH between 5 and 6.8 is fine. A short time a bit outside of this range should not cause any real problems but try and keep it within the recommended levels as much as possible.

When the pH is outside the recommended range the plant will not be able to take up certain vital nutrients and therefore the growth will slow and severe cases the plant will starve.

Why does the pH of my nutrient solution go UP?

Assuming your system is set up correctly, this is normal and desirable in the vegetative period. It means that the plants are growing strongly, as they should be. If it occurs later than about four weeks into the bloom period it may mean that nitrogen levels are too high.

Another cause of dramatic fluctuation of the pH is the reservoir being too small to cope with normal pH fluctuation.

Why does the pH of my nutrient solution go DOWN?

Assuming your system is set up correctly, this will often occur in the bloom phase as the plants take up nutrients in different ratios. Normally, the pH drop is not as large as the pH rise in the growth phase. If it does drop significantly it could be root diseases attacking your plants or an undersized reservoir.

Always check your roots for disease.

What is a pH meter and do I need one for my grow room?

A pH meter is a small electronic device that is used to accurately measure the pH of a solution.

It works by a glass probe detecting the tiny voltage produced when the hydrogen ion in the solution makes contact with the glass probe. The more hydrogen in solution the more acidic the solution is. The meter will give a reading of a whole number followed by one or more decimals, 0.0-6.9 is acidic, 7.0 are neutral and 7.1 - 14.0 is alkaline.

It is very important to maintain the correct pH levels. Colorimetric pH measuring kits are also available but not as accurate. As all meters are inclined to drift, they become inaccurate over time. They need to be calibrated regularly.