CWS Point-of-Use vs Point-of-Entry Systems 3 â Questions and Answers
Question 1: A customer's water report shows high levels of arsenic only in drinking water samples. Which treatment approach does the WQA typically recommend first?
- POE chlorination system
- POU reverse osmosis or POU anion exchange (Correct answer)
- POE water softener
- POE sediment filter
Correct answer: POU reverse osmosis or POU anion exchange
For arsenic reduction, a POU RO or POU anion exchange (for arsenate) is commonly recommended because treatment at the drinking outlet is highly effective and avoids whole-house treatment costs.
Question 2: In a POE system serving a single-family home, the treatment device is typically installed:
- Under the kitchen sink
- On the cold-water line after the pressure tank or meter (Correct answer)
- At each individual bathroom fixture
- Inside the water heater
Correct answer: On the cold-water line after the pressure tank or meter
POE equipment is placed on the main supply lineâusually after the pressure tank (private well) or after the meter (municipal)âso it treats all water entering the home.
Question 3: Which of the following contaminants is BEST addressed by a POE system rather than a POU system?
- Lead from a kitchen faucet cartridge
- Hydrogen sulfide causing odor from all hot and cold faucets (Correct answer)
- Arsenic at the drinking tap
- Chlorine taste at one sink
Correct answer: Hydrogen sulfide causing odor from all hot and cold faucets
Hydrogen sulfide that affects all fixturesâincluding showers where inhalation is a concernâwarrants a whole-house POE treatment solution.
Question 4: A POU drinking water system is certified under NSF/ANSI Standard 58. This standard covers:
- Whole-house softeners
- Reverse osmosis drinking water treatment systems (Correct answer)
- Point-of-entry iron filters
- Atmospheric water generators
Correct answer: Reverse osmosis drinking water treatment systems
NSF/ANSI 58 is the standard for reverse osmosis drinking water treatment systems, covering contaminant reduction, structural integrity, and materials safety.
Question 5: When comparing maintenance requirements, POE systems generally require:
- More frequent filter changes because they handle larger volumes of water (Correct answer)
- No maintenance once installed
- Less maintenance than POU systems because they use larger media beds
- Maintenance only at the specific tap being treated
Correct answer: More frequent filter changes because they handle larger volumes of water
POE systems treat all household water, exposing media and filters to higher total volumes, which typically requires more frequent or larger-scale media replenishment and backwashing.
Question 6: A whole-house POE activated carbon system is primarily used to reduce:
- Total dissolved solids and nitrates
- Chlorine, chloramines, and volatile organic compounds throughout the home (Correct answer)
- Hardness and scale in all fixtures
- Iron and manganese in drinking water only
Correct answer: Chlorine, chloramines, and volatile organic compounds throughout the home
POE carbon systems reduce chlorine, chloramines, and VOCs from all water used in the home, including showers where chloroform inhalation can occur.
Question 7: A POU system under a sink treats only cold water. To also treat hot water at the same location, the installer would need to:
- Install a separate POE softener upstream
- Add a second POU treatment train on the hot-water line feeding that faucet (Correct answer)
- Replace the water heater with a tankless unit
- Install a bypass valve on the main line
Correct answer: Add a second POU treatment train on the hot-water line feeding that faucet
Most under-sink POU systems treat only the cold-water supply; treating hot water at the same point requires an additional POU unit on the hot-water branch.
CWS Point-of-Use vs Point-of-Entry Systems 3
A customer's water report shows high levels of arsenic only in drinking water samples.
Which treatment approach does the WQA typically recommend first?