Filtration and Circulation Systems Flashcards

What is the primary purpose of a multiport valve on a sand filter?

Answer: To direct water flow through different filter operating modes

A multiport valve allows the operator to direct water through different flow paths for filtering, backwashing, rinsing, waste, recirculating, and closed positions.

During a backwash cycle on a sand filter, which direction does water flow through the filter bed?

Answer: Upward through the sand

During backwash, water flows upward through the filter media, lifting and agitating the sand to flush out trapped debris.

A cartridge filter should be cleaned when the pressure differential between inlet and outlet reaches what threshold?

Answer: 10 psi above starting pressure

A cartridge filter should be cleaned when the pressure differential rises 10 psi above the clean starting pressure.

What type of filter media is used in a diatomaceous earth (DE) filter?

Answer: Fossilized diatom skeletons coated on grids

DE filters use grids or fingers coated with diatomaceous earth — the fossilized remains of microscopic algae — as their filter media.

What is 'channeling' in a sand filter?

Answer: A condition where water bypasses the media through cracks or channels

Channeling occurs when water finds preferential pathways through cracks or voids in the filter media, bypassing proper filtration.

What is the typical turnover rate requirement for a public swimming pool?

Answer: Every 6 hours

Most regulations require the entire pool volume to be turned over (filtered) at least once every 6 hours.

Which component prevents backflow of water from the pool into the potable water supply when filling?

Answer: Air gap or backflow preventer

An air gap or approved backflow prevention device is required to prevent cross-contamination between the pool fill water and the potable water supply.