Sand Filter is commonly used for swimming pool for keeping the pool water clean and clear. There are some koi pond owners use Sand Filter in the final stage of filtration process to polish their pond water. In my ten years of keeping koi, I have also installed a sand filter for my pond system but I have merely ran it for six months. The sand filter and the centrifugal pump that is required to feed the sand filter has since idled.
I must agree that Sand Filter is excellent in polishing the pond water and the end result is a crystal clear pond water which allow me to see the base of my 5ft deep pond easily. The sand filter that I used was filled with sand and some zeolite and to push the water through the filter, a 1HP centrifugal pump is used to pump the water from the last stage of filtration and the water return to the pond after the polishing process.
1 Horse Power or 750watt equal to the power consumption of 5 Tsurumi pump and that is a lot. The use of Sand Filter immediately pump up my electricity bill substantially and that is one main reason that discourage me from using it further.
After using the Sand Fitler for one day, you will notice that the presure built up in the piping system leading to the sand filter increased substantially and there is always a need to backwash the filter once a day to clear the clog and reduce pumping presure. Having to do that is quite troublesome and in the process of backwashing, you will lost quite a lot of pond water as well.
Overall, the Sand Filter is easy to install. The PVC pipe require for the installation are that of greater thickness that are able to withstand high operating presure of the sand filter.
After using the sand filter for a few months, you will notice that the backwash action will not reduce operating pressure very much and that indicate that the sand has clog up quite alot and there is a need to open up the sand filter chamber to clean the sand inside.
A filter that require too much maintenance is not fun in koi keeping hobby and finally I gave up the use of sand filter after only six months of use.