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 recommended particle filtration size rating for diatomaceous earth (DE) filters?
Answer: 1–3 microns
DE filters can trap particles as small as 1–3 microns, making them the finest filtering media among the three common pool filter types.
Which condition in a cartridge filter MOST directly reduces flow rate and increases filter pressure?
Answer: Debris and biofilm clogging the pleats
Accumulated debris and biofilm in the cartridge pleats restrict water passage, causing pressure to rise and flow rate to drop.
A pool operator mentions the sand filter requires backwashing every day instead of the normal weekly schedule. The inspector should suspect:
Answer: Algae bloom or heavy organic contamination
Unusually rapid filter fouling typically indicates heavy organic loading from an algae bloom, storm debris, or unusually high bather load.
When inspecting a cartridge filter, the inspector notices the end caps are cracked. This defect is significant because:
Answer: Water can bypass the filter media through the cracks
Cracked end caps create a path for unfiltered water to pass around the cartridge media entirely, defeating filtration.
What is the correct pressure at which a pool inspector should note a DE or sand filter as requiring immediate attention due to over-pressure risk?
Answer: At or above the filter's maximum rated pressure (commonly 50 PSI)
Operating at or above the manufacturer's maximum rated pressure (often 50 PSI for residential filters) risks tank failure and is a safety hazard requiring immediate attention.
Which component in a sand filter directs water flow to different modes and is the MOST common source of internal leaks?
Answer: Multiport valve spider gasket
The spider gasket inside the multiport valve seals each port channel; when it cracks or warps, water leaks between positions, causing poor filtration or backwash bypass.
A cartridge filter tank has a split or bulging outer shell. An inspector should classify this as:
Answer: A safety hazard requiring the filter to be taken out of service
A split or bulging filter tank indicates structural failure under pressure and is a serious safety hazard that warrants immediate decommissioning.