Turn off the flow of water to the filter housing. In some cases, this means turning off the pool's pump. If you have a diverter valve, you can divert the flow of water from the filter.
Remove the lid from the filter and pull the filter media out of the filter housing. This process depends on the type of filter you have. Follow normal filter changing process for your filter.
Sop all of the water out of the housing, using a wet towel. Dry off the inside and outside of the housing.
Use a rotary tool equipped with a V-groove cutter to cut a groove along the crack on the inside of the filter housing. Extend the groove approximately a quarter inch past each end of the crack. Cut the groove on the inside of the housing, because water will naturally push the epoxy into the crack and not out of it. Always seal from the inside, if possible.
Mix the two-part epoxy together with a toothpick and fill the V-groove with it. Overflow the epoxy onto the sidewall of the housing. Allow 24 hours drying.
Place the filter back into the housing and reinstall the lid. Turn the water back on and check for leaks.