All city water, by law, is required to have a level of chlorine or chlorine type chemical added to it. The purpose of adding chlorine to the water is to kill any bacteria or parasites in the water that might present a threat to public health. The problem with chlorine in the water is that it can be very harmful to koi. Chlorine in the water at low levels will burn the gills of a koi. At higher levels it will kill them.
Adding chlorinated water to a pond in small increments is typically not a problem because the chlorine will usually evaporate before it has a chance to build up. If, on the other hand, you are adding a large amount of chlorinated water at one time you will need to either remove the chlorine from the water before it enters the pond or neutralize it once it enters the pond. You have two options.
The Advantage Carbon Filter is designed to automatically remove any chlorine from city water before it enters your koi pond. Each filter contains over one cubic foot of activated carbon media. Additionally, these filters come with an automatic backwash system. Depending on the amount of water you are sending through the filter you can program it to automatically backwash from once to several times a week. This back washing assures the filter will stay clean and never begin to channel. Channeling is what occurs when a filter starts to plug up and the water begins to create a channel through the filter media. When this happens the water is exposed to only a fraction of the filtering media rather than flowing evenly through all the media thereby greatly reducing the filters efficiency.
How often do you need to replace the carbon media in the Advantage Carbon Filter?
There are a number of variables to consider as to how often the carbon needs to be replaced such as;
If you are only changing 200 gallons a week on average in your pond, you allow your auto fill to slowly replace the water and the chlorine level in your city water is .02%, one cubic foot of carbon would probably last 5 years without changing.
On the other hand, if you are changing 3,000 gallons a week on average in your pond, you are using a garden hose to quickly refill the pond and the chlorine level of your city water is .05%, one cubic foot of media would probably last 1 1/2 to 2 years.
If you want to be overly cautious you can just change out the carbon once a year. Because carbon filters loose their ability to filter out chlorine very slowly, another option is, after the first year, to start testing the fill water coming from the carbon filter once a month for chlorine. Then, at the first sign of any chlorine in the water, change out the carbon. This will now tell you, in the future, how long you can go before you need to change out the carbon in the filter again.