ro/di system maintenance

Good water quality is essential for successful reef-keeping. Reverse osmosis water purification systems have become the number-one way of ensuring the water used for top-offs and to mix saltwater are free of toxins and algae-promoting nutrients, but for optimum filtration they do require regular maintenance.   If not serviced on a regular basis, RO systems produce less water and begin to let contaminants pass through the filter system. We’ll look at the main serviceable components of an RO system and explain how to service each part of your system. If you take care of your RO system it will always provide pure water when you need it.


Sediment Prefilter

The prefilter captures large particles like sand, iron particles and mineral scale which can exhaust your other, finer filters very quickly.  As the prefilter clogs, it gets harder for the water to pass through and move on to the other filtration stages.  This filter needs to replaced every six months or sooner if you notice a decline in water production.


Activated Carbon Cartridge

Activated carbon cartridges can contain either granular carbon or a solid carbon block.  The carbon cartridge removes chlorine, chloramine, pesticides and pharmaceuticals.  Like the sediment filter, Carbon need to be changed around every six months as they will eventually clog with particles or even bacterial slime.


Reverse Osmosis Membrane


This is a spiral wound semi-permeable membrane, which “rejects” minerals, salts, nitrate, phosphate and heavy metals, sending them down the wastewater drain.  The RO membrane can become fouled with calcium carbonate, bacteria and other contaminants.  One way to maintain the membrane is to use a RO Flush Kit to blast it with water and wash away most of the blockage.  You will know it is time to replace the RO membrane if you see an increase in pollutants like nitrate, phosphate or water hardness in the filtered water. You can also use a total dissolved solids (TDS) meter to monitor the water quality which quickly degrade when the membrane is exhausted.


Deionization Cartridge

The DI cartridge is the last stage in most RO/DI systems and is filled with deionization resin.  DI resin strips out any traces of pollutants that slip past the RO membrane .  If you continue to use a DI cartridge after its exhausted your product water can come out with a slight fishy odor. A TDS meter can also check for water purity.  Many DI cartridges will actually contain color changing resin to give you an indication of when it is time to swap it out or yo can use a TDS meter to check if your water is still coming out pure.


Hoses and Fittings

Make sure to hand-tighten all fittings after performing maintenance, but If a fitting leaks, reseat the hose and hand-tighten once again.  Replace cracked or poorly-seating hoses before a leak can occur


Filter Canisters and Housings

The major parts of the RO/DI system are the Canisters which hold the cartridges and the housings which hold the RO membrane.  An O-ring creates the seal in the opening or each but can stretch or crack over time so replace the O-ring every year or if you see drips.


How to Replace Your RO/DI Filter Cartridges Tutorial