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 type of sand is recommended for pool sand filters, and what is the standard mesh size?
Answer: #20 silica sand (0.45–0.55 mm)
#20 grade silica sand (0.45–0.55 mm particle size) is the industry-standard media for pool sand filters because it balances filtration efficiency with adequate flow rate.
How often should cartridge filter elements typically be replaced under normal residential pool use?
Answer: Every 1–2 years
Under normal conditions, cartridge elements typically last 1–2 years before the media degrades enough that even thorough cleaning cannot restore adequate flow and filtration.
An inspector finds a DE filter with no pressure gauge installed. This is a concern because:
Answer: Without a gauge, operators cannot determine when the filter needs servicing
A pressure gauge is essential for all filter types to monitor clean baseline pressure and identify when the filter is dirty and needs servicing.
What maintenance step is recommended for cartridge filters at least once per season but NOT required for sand or DE filters?
Answer: Soaking the cartridge in a filter cleaning solution overnight
Cartridge elements benefit from an overnight chemical soak in a filter cleaner solution to dissolve oils and scale that hosing alone cannot remove.
Which filter type requires NO backwashing and is typically cleaned by removing and hosing down the element?
Answer: Cartridge filter
Cartridge filters are cleaned by removing the element and hosing it off; they have no backwash valve because water flows from outside-in through the media.
When a sand filter is set to 'Recirculate,' water is routed:
Answer: From the pump directly back to the pool, bypassing the filter media
Recirculate bypasses the sand bed entirely, allowing pool water to circulate for chemical mixing or treating without passing through the filter media.
A pool inspector should flag a DE filter that lacks a separation tank (or equivalent) on the backwash line because:
Answer: Discharging DE to a municipal sewer without settling may violate local codes
Many municipalities prohibit discharging diatomaceous earth directly into the sewer system; a separation tank allows DE to settle out before the water is discharged.