Cartridge-type filters are those where the cartridge itself is the filter aid. Cartridge filters can be either pressure or vacuum-type and are subject to the same general piping and tank specifications as diatomite-type filters. Replacement cartridges are divided into two types: depth and area. General specifications, however, are the same for both. Cartridge filters shall not require the addition of any flocculating agents such as ammonium alum, aluminum sulfate or potassium alum. They shall be subject to the same requirements listed under Section 1339.04 for all types of filters. All types of cartridges shall have sufficient structural strength to resist rupturing, channeling, collapsing or bursting at a maximum pressure differential of fifty psi. Cartridge seals shall be so designed as to prevent any bypassing of unfiltered water. If provision is made for backwashing, it shall be so arranged as to not permit any backwash water to enter the recirculating system. No residue shall be permitted to remain in the filter housing that could be picked up in the next filtering cycle.
Cartridge elements shall be divided into two types:
(a) Depth-type cartridges are elements where the porosity varies from the inlet to the discharge surface. They shall have sufficient depth to provide adequate dirt-holding capacity and be designed for a flow of no more than one gallon per minute per five cubic inches of volume with a pressure drop not to exceed two psi across clean cartridges and not to pass any particulate matter larger than twenty-five microns.
(b) Area or surface-type cartridges are those which rely on the surface area for their dirt-holding capacity and they shall follow the same flow per square foot of area as diatomite filters, namely three gallons per minute per square foot of area for pressure filters and two and one-fourth gallons per minute per square foot of filter area for vacuum filters.
(c) The filter shall be capable of filtering the entire contents of a pool in eighteen hours or less.
(d) Filter capacity shall be such that it need not be cleaned more frequently than once every four days under proper conditions of water and operation.
(e) All filters shall be designed so as to permit easy removal of the cartridges.
(Ord. B-751. Passed 7-9-62.)