Reverse osmosis: Which filters and when to change?
Standard 3 stages RO
The large 5-stages reverse osmosis units are produced in
Filter No. 2 in the standard system from the Far East is an active carbon filter (Granulated Active Carbon), which consists of baked carbon particles that have large capacity to absorb chlorine and other chemicals. Europe does not have the same amount of chlorine in the water as in for example USA. Therefore the active carbon filter (GAC) is not as relevant in Europe - but use it anyway.
Filter no. 3 is a carbon Block filter that is better than a GAC carbon filter. It weighs more than the GAC filter.
It looks like this:
You just use the RO system as it is the first 6-12 months. After this period of time it is recommended to replace the active carbon filter with a sediment filter 1µ.
System with 2 filter housings 10"
System with 3 filter housings 10"
System with 3 filter housings 10" + optional harpiksfilter
System with 3 filter housings 10", where 3rd filter housing is used as DI filter
When to change filters and membrane?
The more often you change your filters, the better protected is the membrane and the longer the membrane lasts, and since the membrane is significantly more expensive than the filters, it makes good sense.
The 10" filters for the large filter housings have a capacity of 11.000 liters or 3.000 Gallons. The small inline filters for the small 3 stages systems has a capacity of 6.000 liters or 1.500 Gallons. Remember to calculate with your waste water factor.
If you make 100 liters of osmosis water a week with a membrane having a waste water factor of 3, you have 100 +300 = 400 liters of water a week through your filters. That makes 400 * 52 = 20,000 liters a year.
Otherwise you measure when what should be changed:
Immediately after installing a new system you measure:
The serious user monitors these values permanent with a TDS Monitor, that measures at two points simultaneously.
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