Water and water treatment is a complex business. The quality of water, suburb-to-suburb, city-to-city varies significantly.
Firstly, Australian water providers are dealing with an arid climate. Cities like Perth have large populations while having limited water resources. Due to this, the water that we receive is undoubtedly compromised by this factor.
Secondly, we have miles upon miles of pipes that feed our homes with the water that we use at significant rates. There is not much point spending millions of dollars on water treatment if the water, after leaving the catchments, is polluted in the pipeline system before it is consumed or (in this case) fed to plants.
Ultimately, water is a controversial subject. Suspect water supplies are played down by Water Authority spin-doctors. According to our Water Authorities our water is of pristine quality. Critics, however, argue strongly against this. Chlorine, fluoride, metals (alum, iron, lead), bacteria and so on are just some of the things found in scheme water supplies. Leaching of contaminants into ground water supplies, and nasties known as THM’s (Trihalomethanes) — chlorine combining with humic acid from decayed leaves, soil, algae and other natural debris are ever present’ dangers in scheme water. Dangerous because they are carcinogenic.
In fact, a 1983 report on South Australian drinking water concluded that the THM concentrations in the water supply were among the highest in the world!
Once you have created the right environment, provided the right nutrition, and optimized everything in the grow room the rest comes down to water. Plain old water! Hydroponics at this point becomes 99% H20.
So, how to get decent water?
Water Filtration – High Flow Water Filter
The Easiest way to make a big difference to your Water Quality is to use one of our High Flow Water Filters -FINEST CARBON MATRIX FILTER IN THE INDUSTRY @ 1 micron! The combination of a quality sediment filter and Carbon Filter means around 95%+ of contaminants are removed with NO LOSS OF WATER FLOW!!!
This is a big advantage as RO whilst being LAB standard is very slow and depending on water quality can discard large amounts of salty water.
Simply plug inline with snap fit hose fittings or we can provide different fittings for permanent installation with either 1/4 (4mm) or 3/4(6mm) High Pressure hosing.
Reverse Osmosis – Reverse Osmosis Water Filter
To understand Reverse Osmosis (RO), it is necessary to understand the process of osmosis. In living things, osmosis is frequently seen. The component parts include a pure or relatively pure water solution and a saline or contaminated water solution, separated by a semi-permeable membrane.
The semi-permeable membrane is so designated because it permits certain elements to pass through it while blocking other elements. The elements that pass through the membrane include water, usually smaller molecules of dissolved solids, and most gases.
A fundamental scientific principle now comes into play. That is, dissimilar liquid systems will try to reach the same concentration of materials on both sides of the membrane. The only way for this to occur is for the pure water to pass through the membrane to the saline side of the membrane. This attempt to reach equilibrium is called osmosis.
In the early 1950’s an Indian scientist (Sourirajan) working at the University of California discovered that by reversing osmosis saline water could be purified. This was achieved by reversing the natural osmotic flow and forcing salt water, under pressure, through a permeable membrane. Through this process tiny water molecules were able to penetrate the membrane while larger salt molecules remained outside the membrane.
By collecting only the water that had penetrated the membrane an almost pure H2O product could be obtained.
Reverse Osmosis for Scheme Water
What’s in Tap Water?
Salts analysis test conducted on a sample of Perth scheme water.
- Phosphate 1.69
- Nitrate 0.15
- Ammonium 0.18
- Potassium 7.7
- Calcium 41.9
- Magnesium 14.4
- Sulphate 12.3
- Iron 0.07
- Sodium 161
- Chloride 202
- EC (mS cm-1) 0.78
Tap water supplies, as can be seen, contain moderate to high levels of salts.
The average Perth water supply will be a combination of bore and dam water. The mixing ratio of bore/dam water is dependent on which water tower (based on location) the water is drawn from. In some areas there may be as much as 90% bore water in your tap water supply.
Perth tap water contains salts at between 0.8 – 1.2 EC (again, dependent on which area you live in). This means that the water you are using in your hydroponics system begins at a relatively high EC. For instance, if the tap water was 1.2 (12) and you were in grow with a total EC of 1.8 (18) there would be minimal levels of balanced food salts available to the plants.
The only way to give the plant/s more food is:
- A) Up the EC to 2.0-2.2 (or)
- B) Reduce the existing salt levels in the water
Option A would mean higher levels of salts and therefore an increased possibility of salt build up in the medium and in the root system of the plants.
Option B would mean using rainwater, distilled water, or tap water that had been filtered through Reverse Osmosis.
The Advantages of Reverse Osmosis
The EPA recommends reverse osmosis as the most satisfactory technology for removing impurities from water. With the exception of distillation, reverse osmosis is the only known process that & they remove turbidity, sediment, colloidal matter, total dissolved solids, toxic metals, radioactive elements, pesticides and herbicides.
The energy (to output ratio) used for reverse osmosis is far superior to that of distillation energy required is mains pressure which forces the pure water through the permeable membrane. Disoflira,on the other hand requires high energy usage to water output as it is necessary to boil water through some other form of energy such as gas.
Reverse Osmosis Filtration
RO water has a salt content of approximately 0.02 EC.
RO filtration systems have at least one carbon filter before the permeable membrane to remove chlorine from the water prior to RO treatment. This is because the membrane will degrade rapidly if subjected to chlorine.
A basic household RO system that runs off mains pressure will filter the water through a carbon pre-filter, then the RO membrane, and finally through a second carbon filter.
A reverse osmosis system for hydroponics that runs off mains pressure will differ somewhat from this due to the amounts of water that are required to pass through it. For smaller amounts of water (between 50-100 litres a week) a sediment pre-filter, carbon pre-filter, then RO membrane unit would suffice. For more intense use (100 litres or more a week) a sediment pre-filter, carbon pre-filter, a second carbon filter, then RO membrane would be better suited to the job.
In addition to this, the larger the carbon and sediment filters the RO system utilizes, the higher the volume they will produce before they become contaminated.
Quantity is Quality!
The quality of carbon filters, and permeable membranes can vary greatly when it comes to RO filtration units. In addition to this, there is some questionable advice and support being given by some of the suppliers of RO units.
It isn’t unheard of for hydro growers to runoff to their local water filtration supplier and forget to mention just what the RO unit is to be used for. The supplier then assumes that it is for drinking water and sells a unit that is completely unsuitable for the purpose of hydroponics (i.e. large outputs). There is very little point buying a RO unit that is designed for low capacity use when you need high capacity output.
Buying the correct filtration unit to suit your purposes can prove to be a problematic business!
After you purchase your unit you will need to get it serviced on a regular basis. Just how regularly will depend on the volume of output and the quality of your tap water.
This will also depend on the number of, the density of, the size of, and quality of the sediment and carbon filters. Quantity is quality when it comes to high volume output.
The Major Advantage
The major advantage of removing the existing salts from your hydroponics water supply is that it ensures your plants are getting only the best salts. That is, salts that are blended for the purpose of plant growth (in the form of nutrient).
Tap water is that the salts are very random and (mostly) not suitable for plant growth. When you mix nutrient with tap water the balance can be a bit out of whack due to the combination of tap water salts with nutrient salts. Then as your plants uptake water and nutrients, the salts change further.
If you top up your tank with tap water (a combination of salts and H20) and then add more nutrient to bring the salts back to desirable (EC) levels this further throws the blend of salts out of balance.
Eventually you will end up giving your plants completely imbalanced nutrition. This can result in your plants burning due to the imbalanced food that they are receiving. At best their vigor will be affected by various deficiencies and extremes. This is why – if you are using tap water – you should only top up your nutrient tank (in a recycling system) with water and not add further nutrient salts.
By using de-mineralised (salt free) water you are able to ensure that your plants are receiving the correct balance of salts/food between tank changes. Furthermore, because there are no mineral salts in the water, you are able to add water (top up the nutrient tank with water) and nutrient (then add nutrient to the desired salts (EC) level) with every top up of the nutrient tank. Because of this the plants are constantly receiving optimum nutrition. In addition to this, the necessity for nutrient dumps (complete water and nutrient changes) is greatly reduced.