Sand, DE & Cartridge Filtration Flashcards
7 cards from real CPI practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Sand, DE & Cartridge Filtration flashcards as text
What is the typical operating pressure range for a properly functioning sand filter?
Answer: 8–15 PSI
Sand filters normally operate between 8–15 PSI at startup; a rise of 8–10 PSI above the clean baseline signals that backwashing is needed.
Which sand filter component prevents sand from passing back into the pool during normal filtration?
Answer: Lateral assembly
Laterals are slotted tubes at the bottom of the sand bed whose narrow slots allow water through but retain sand particles.
A pool inspector notices the sand filter sight glass remains cloudy after a full backwash cycle. The MOST likely cause is:
Answer: Channeling through the sand bed
Channeling creates bypass paths through the sand so water is never fully filtered, leaving effluent turbid even after backwashing.
DE filter grids must be inspected for which defect that allows DE powder to pass into the pool?
Answer: Tears or holes in the fabric
Torn or deteriorated grid fabric allows DE powder to bypass filtration and return to the pool, appearing as white cloudy material.
What is the correct procedure after adding fresh DE powder to a DE filter following a backwash?
Answer: Add powder directly into the skimmer with the pump running
DE powder is slurried and poured into the skimmer with the pump running so it coats the grids evenly inside the filter.
A cartridge filter element showing pleats that are collapsed or matted together indicates:
Answer: Excessive flow rate or pump oversizing
Collapsed pleats result from excessive flow velocity forcing the filter media together, dramatically reducing effective surface area and filtration efficiency.
Which valve position on a sand filter multiport valve is used to waste backwash water directly to drain WITHOUT sending it through the filter?
Answer: Waste
The Waste position routes water from the pump past the filter and directly out the waste line, used for vacuuming heavy debris or lowering water level.