Published 23 December, 2016

In this article we would like to help you to understand how a reverse osmosis membrane works. The following information is valid for all reverse osmosis membranes, supplied by GrowMax Water or other manufacturers.

A reverse osmosis membrane is made of different polyamide layers through which tap water is filtered. With this process, we obtain a water with a lower EC (with a low salt level) and free of bacteria and virus. The pores of the polyamide layers are able to filter up to 0,0001 microns.

Production specifications of the reverse osmosis membranes

The specification is made by the Membrane Manufacturers and is based on the following parameters:

1 – Water Temperature: 25º C

2 – Water Pressure: 60 psi (4.3 kg/cm3

3 – TDS (Total Dissolved Solids): 500 ppm (0.7 EC)


Therefore the production will increase or decrease according to variations in the above water conditions. Example:

-Water production will decrease by 3.6% for each degree below 25º C. So, if your water temperature is 15ºC, then; 10º (less) x 3.6% = 36% decrease. Now, 20 L/h can be about 13 L/h.

-If the temperature is even lower, let’s say 10ºC, then: 15º (less) x 3.6% = 54% decrease. 20 L/h can now be as low as 9 L/h.
-Also, at the same time if the inlet pressure is lower than 60 psi (4,3 kg) then your production will also decrease.
-Also if the TDS is higher than 500 ppm (EC higher than 0.7), then again, you will have another lower production rate. The higher the EC, more inlet water pressure is needed.

How long will a membrane last?

We cannot know exactly how long a reverse osmosis membrane will last, because it depends on three factors:

1- The quality of the water
2- The amount of water passing thru
3- The amount of waste water.

For example, the higher the EC, the worse is the quality water filtered, means the membrane can sooner be incrusted with salts. The higher the amount of water filtered, the less is the life of the membrane, and the same happens because of the amount of waste water, that is to say, the less waste water amount the sooner the membrane will be full of salts. This last point is very important, so we will explain it in more detail below.

The waste water in RO systems

reverse osmosisAll the reverse osmosis systems must send waste water to the drain. Why? The different polyamide layers of the membrane retain the salts from the water, but that portion of the water doesn’t go to the drain needs to be flushed out of the membrane, so that the membrane doesn’t become incrusted with those salts.

GrowMax has designed its reverse osmosis systems for the Hydroponic and Gardening markets. Because we are not using pressurized holding tanks, different from residential RO units, we have designed our units to REJECT MUCH LESS water than others conventional units.

Most RO systems are designed to reject 4:1, 5:1, 6:1 or more. This means for each liter of water produced, 4, 5 or 6 times of the amount of water is needed and send it to the drain (or garden). GrowMax units are designed to reject only 2:1. This saves a lot of water.

However, the downside to this design is that if the TDS or EC is very high, more than 500 ppm (> 0.7 EC) then the lifespan of the reverse osmosis membrane can be diminished.

GrowMax Water reverse osmosis systems use 150 GPD (Gallon per Day) membranes for the POWER GROW, MEGA GROW and MAXQUARIUM.

This is the highest production membrane currently available in this size and configuration, without using much higher cost membranes that require much higher inlet pressures, pumps and motors.

Reverse osmosis membrane diagram:

membrana osmosis inversa
Accessories to improve the reverse osmosis membrane

bomba-de-presion-para-osmosis-inversaGrowMax offers solutions to improve your installation or help in the case of adverse water conditions. These solutions are different accessories that will help you to boost the membrane production:
If your inlet water pressure is low (less than 40psi/3 kg), you have to install a GrowMax Water Booster Pump to your RO system. This will increase the water pressure to a 4-5 kg constant inlet water pressure. We have a Booster Pump Kit valid for use with POWER GROW and MAXQUARIUM and also a High Flow Booster Pump Kit, valid for use with the MEGA GROW.


In case your water has a high EC level, the membrane can be saturated and clogged sooner. You can change out the FLOW RESTRICTOR in your unit, to a larger flow restrictor, to allow for more water rejection to the drain, thus helping to prolong the life of your membrane.

POWER GROW 400ml 550ml (foto)restrictor-de-flujo
MEGA GROW 550 ml 800ml (foto)
MAXQUARIUM 400 ml 550ml (foto)



Learn more about GrowMax Water Reverse Osmosis Systems designed for hydroponics and gardening.


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