CPO Filtration and Circulation Systems 2 — Questions and Answers
Question 1: What is the primary purpose of a multiport valve on a sand filter?
- To regulate chemical dosing
- To direct water flow through different filter operating modes (Correct answer)
- To control pump speed
- To measure filter pressure
Correct 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.
Question 2: During a backwash cycle on a sand filter, which direction does water flow through the filter bed?
- Downward through the sand
- Horizontally across the laterals
- Upward through the sand (Correct answer)
- In a circular pattern around the tank
Correct answer: Upward through the sand
During backwash, water flows upward through the filter media, lifting and agitating the sand to flush out trapped debris.
Question 3: A cartridge filter should be cleaned when the pressure differential between inlet and outlet reaches what threshold?
- 5 psi above starting pressure
- 10 psi above starting pressure (Correct answer)
- 15 psi above starting pressure
- 20 psi above starting pressure
Correct answer: 10 psi above starting pressure
A cartridge filter should be cleaned when the pressure differential rises 10 psi above the clean starting pressure.
Question 4: What type of filter media is used in a diatomaceous earth (DE) filter?
- Silica sand and anthracite
- Crushed glass beads
- Fossilized diatom skeletons coated on grids (Correct answer)
- Polyester fiber cartridges
Correct 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.
Question 5: What is 'channeling' in a sand filter?
- The normal pathway water takes through clean sand
- A condition where water bypasses the media through cracks or channels (Correct answer)
- The process of adding new sand to the filter
- A method of distributing water evenly across the sand surface
Correct 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.
Question 6: What is the typical turnover rate requirement for a public swimming pool?
- Every 2 hours
- Every 6 hours (Correct answer)
- Every 12 hours
- Every 24 hours
Correct answer: Every 6 hours
Most regulations require the entire pool volume to be turned over (filtered) at least once every 6 hours.
Question 7: Which component prevents backflow of water from the pool into the potable water supply when filling?
- Pressure relief valve
- Check valve
- Air gap or backflow preventer (Correct answer)
- Gate valve
Correct 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.
CPO Filtration and Circulation Systems 2
What is the primary purpose of a multiport valve on a sand filter?