Career upgrade: Learn practical AI skills for better jobs and higher pay.
Level up
PracticeVideosBlogFlashcardsEspañol
All Practice Exams

100+ Free CHWS Practice Questions

Pass your BONENT Certified Hemodialysis Water Specialist exam on the first try — instant access, no signup required.

✓ No registration✓ No credit card✓ No hidden fees✓ Start practicing immediately
~60–70% Pass Rate
100+ Questions
100% Free
1 / 100
Question 1
Score: 0/0

A dialysis water specialist discovers the facility is served by a private well rather than a municipal water supply. An additional concern not present with municipal water is:

A
B
C
D
to track
Same family resources

Explore More BONENT Nephrology Technology Certifications

Continue into nearby exams from the same family. Each card keeps practice questions, study guides, flashcards, videos, and articles in one place.

BONENT CHBT Certified Hemodialysis Biomedical Technician

Practice Questions

BONENT CHT Certified Hemodialysis Technologist

Practice Questions
2026 Statistics

Key Facts: CHWS Exam

150

Exam Questions

BONENT CHWS

3 hrs

Exam Time

BONENT

70

Passing Score (MSPS)

BONENT all exams

20%

Water Purification Equipment

Largest domain

$235–255

Exam Fee (USA)

BONENT 2026

≥10 min

Carbon EBCT for Chloramine

AAMI minimum

The CHWS exam contains 150 questions over 3 hours. Water Purification Equipment is the largest domain at 20%, covering RO, pretreatment, deionization, UV, and distribution loop design. Eligibility requires 1–3 years dialysis water experience depending on education level. BONENT certification demonstrates mastery of AAMI/ISO 13959 water quality standards, contaminant hazards, and disinfection practices essential for patient safety in hemodialysis.

Sample CHWS Practice Questions

Try these sample questions to test your CHWS exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1Which federal law establishes maximum contaminant levels (MCLs) for public drinking water supplied to dialysis facilities?
A.Safe Drinking Water Act (SDWA)
B.Clean Water Act (CWA)
C.Resource Conservation and Recovery Act (RCRA)
D.Toxic Substances Control Act (TSCA)
Explanation: The Safe Drinking Water Act (SDWA, 1975) establishes EPA primary and secondary MCLs for public water supplies. Dialysis facilities receive municipal water regulated under SDWA, which sets baseline contaminant limits before facility-level treatment achieves AAMI/ISO product water standards.
2Under CMS Conditions for Coverage for end-stage renal disease (ESRD) facilities, which individual is ultimately responsible for the water treatment program?
A.Clinical Manager
B.Medical Director
C.Biomedical Technician
D.Governing Body
Explanation: CMS ESRD Conditions for Coverage assign the Medical Director ultimate physician-level responsibility for the water treatment program, including policy approval and corrective-action oversight. The biomedical technician performs day-to-day monitoring; the clinical manager oversees nursing operations.
3The FDA classifies dialysis water treatment systems as which device type requiring 510(k) premarket notification?
A.Class I exempt device
B.Class II device
C.Class III device requiring PMA
D.Humanitarian Use Device (HUD)
Explanation: Dialysis water treatment systems are FDA Class II medical devices subject to 510(k) premarket notification, general controls, and special controls. Class II classification reflects moderate risk and substantial equivalence to predicate devices; Class III requires full PMA and applies to high-risk implantable devices.
4AAMI/ANSI/ISO 13959 sets the action level for bacteria in hemodialysis product water at less than:
A.50 CFU/mL
B.100 CFU/mL
C.200 CFU/mL
D.500 CFU/mL
Explanation: AAMI/ANSI/ISO 13959 establishes an action level of <100 CFU/mL and a maximum allowable level of <200 CFU/mL for bacteria in hemodialysis product water. Exceeding the action level triggers investigation and corrective action before the maximum is reached.
5The AAMI/ISO maximum allowable endotoxin level in hemodialysis product water is:
A.0.125 EU/mL
B.0.25 EU/mL
C.0.5 EU/mL
D.1.0 EU/mL
Explanation: AAMI/ANSI/ISO 13959 sets the endotoxin action level at <0.25 EU/mL and the maximum allowable level at <0.5 EU/mL for hemodialysis product water. Ultrapure dialysate (used in HDF) has stricter limits: <0.03 EU/mL action and <0.1 EU/mL max.
6For dialysate (not product water), AAMI/ISO 13959 sets the bacteria action level at less than:
A.50 CFU/mL
B.100 CFU/mL
C.200 CFU/mL
D.500 CFU/mL
Explanation: AAMI/ANSI/ISO 13959 sets the dialysate bacteria action level at <50 CFU/mL and maximum at <100 CFU/mL — half the corresponding product water thresholds. Dialysate contacts the dialyzer membrane and thus requires stricter control than product water alone.
7NSF International is involved in dialysis water treatment primarily through:
A.Setting federal MCLs for drinking water contaminants
B.Certifying water treatment components to performance standards
C.Requiring 510(k) submissions for RO membranes
D.Issuing interpretive guidelines for CMS V-tags
Explanation: NSF International (National Sanitation Foundation) is a standards development and product-certification organization. NSF/ANSI standards (e.g., NSF 61 for materials in contact with drinking water) certify that plumbing components and water treatment equipment meet performance and safety criteria relevant to dialysis systems.
8Hardness in water is caused primarily by dissolved:
A.Sodium and potassium ions
B.Calcium and magnesium ions
C.Iron and manganese ions
D.Chloride and sulfate ions
Explanation: Water hardness is defined by dissolved calcium (Ca²⁺) and magnesium (Mg²⁺) ions. These divalent cations scale equipment, foul RO membranes, and exhaust water softener resin. Hardness must be removed before water reaches the RO to protect membrane life and product water quality.
9In an ion exchange water softener, calcium and magnesium ions are removed by being exchanged with:
A.Hydrogen ions (H⁺)
B.Sodium ions (Na⁺)
C.Chloride ions (Cl⁻)
D.Potassium ions (K⁺)
Explanation: Cation exchange resin in a water softener is regenerated with NaCl (brine). Ca²⁺ and Mg²⁺ ions in feed water displace Na⁺ from the resin beads, hardening the resin while releasing sodium into the softened water. Regeneration restores Na⁺ sites by flushing concentrated brine through the resin bed.
10Chloramine (monochloramine) is formed when municipal water plants combine chlorine with:
A.Fluoride
B.Ammonia
C.Bicarbonate
D.Sulfate
Explanation: Monochloramine (NH₂Cl) forms when chlorine reacts with ammonia (NH₃) added by municipal water utilities as a secondary disinfectant. Chloramine is a more stable disinfectant than free chlorine, persists longer in distribution systems, and is more difficult to remove — requiring activated carbon with adequate empty bed contact time.

About the CHWS Exam

The CHWS certification validates specialized expertise in dialysis water treatment — the critical system that purifies municipal water to AAMI/ISO 13959 standards before it contacts patients during hemodialysis. The 150-question, 3-hour exam covers seven domains: Water Quality Standards (15%), Water Treatment Terminology (5%), Basic Water Chemistry (15%), Risks & Hazards of Inadequately Treated Water (15%), Water Purification Equipment (20%), Water System Performance & Monitoring (15%), and Disinfection Strategies (15%). Key technical areas include AAMI bacteria/endotoxin limits, RO membrane performance, carbon EBCT for chloramine removal, biofilm management, and chemical disinfection verification.

Questions

150 scored questions

Time Limit

3 hours

Passing Score

70 scaled score (MSPS)

Exam Fee

$235–$255 (Board of Nephrology Examiners Nursing and Technology (BONENT))

CHWS Exam Content Outline

20%

Water Purification Equipment

Pretreatment (multimedia, carbon, softener), reverse osmosis (single/double-pass, rejection, recovery), deionization, UV, ultrafiltration, distribution loop design, system design, and vendor selection

15%

Water Quality Standards

SDWA, FDA (510k, GMP), AAMI/ANSI/ISO 13959 chemical and microbiological limits, CMS Conditions for Coverage (V-tags), and water quality associations (NSF, AWWA, WQA)

15%

Basic Water and Water Quality

Water chemistry (pH, ions, hardness, redox), hydrologic cycle, contaminant sources, acids, bases, and fundamental analytical chemistry

15%

Risks & Hazards of Inadequately Treated Water

Chloramine toxicity (hemolysis), aluminum (encephalopathy), fluoride, copper, endotoxin (pyrogenic reactions), microbiological contaminants, source water surveillance

15%

Water System Performance and Monitoring

Microbiological culture methods, LAL endotoxin testing, chloramine (DPD) testing, conductivity, hardness titration, automated/manual monitoring, trending, and system failure investigation

15%

Disinfection Strategies and Prevention Practices

Chemical disinfection (PAA, bleach, formaldehyde, ozone), thermal sanitization, biofilm management, residual testing, high-level disinfection, and outbreak remediation

5%

Water Treatment Terminology and Acronyms

Core industry terminology, units of measure (gpg, EU/mL, CFU/mL, µS/cm), and calculation formulas for EBCT, recovery, rejection, and log reduction

How to Pass the CHWS Exam

What You Need to Know

  • Passing score: 70 scaled score (MSPS)
  • Exam length: 150 questions
  • Time limit: 3 hours
  • Exam fee: $235–$255

Keys to Passing

  • Complete 500+ practice questions
  • Score 80%+ consistently before scheduling
  • Focus on highest-weighted sections
  • Use our AI tutor for tough concepts

CHWS Study Tips from Top Performers

1Memorize AAMI/ISO 13959 limits: bacteria product water <100 CFU/mL action / <200 max; endotoxin <0.25 EU/mL action / <0.5 max
2Know dialysate limits separately: bacteria <50 CFU/mL action / <100 max; endotoxin <0.125 EU/mL action / <0.25 max
3Carbon EBCT ≥10 min for chloramine removal; calculate EBCT = bed volume ÷ flow rate
4DPD method is the AAMI-recommended field test for chloramine; test before every treatment session
5Understand RO performance: % Rejection = (Feed − Permeate conductivity) / Feed × 100; Recovery = Permeate flow / Feed flow × 100
6Know the clinical toxicity syndromes: chloramine → hemolysis; aluminum → encephalopathy; endotoxin → pyrogenic reactions
7Distribution loop design: continuous recirculation, minimize dead legs (<1.5× pipe diameter), use heat-fusible materials (PVDF), avoid solvent-cemented PVC
8UV at 254 nm kills bacteria but does NOT remove endotoxin; ultrafilters (UF) are needed for endotoxin retention
9CMS V-tag surveys require 3 years of water quality documentation; monthly cultures, pre-treatment chloramine testing logs
10Understand disinfectant residual verification: PAA requires PAA-specific test; bleach requires DPD chlorine test; both must confirm zero residual before patient use

Frequently Asked Questions

What is the CHWS certification?

The CHWS (Certified Hemodialysis Water Specialist) is a BONENT credential for professionals who design, operate, and maintain water treatment systems in hemodialysis facilities. It validates mastery of AAMI/ISO 13959 water quality standards, purification equipment, monitoring methods, and disinfection practices that protect dialysis patients from waterborne contaminants.

How many questions are on the CHWS exam?

The CHWS exam contains 150 multiple-choice questions and has a 3-hour time limit. It is offered in paper-and-pencil format at approved testing sites and as computer-based testing (CBT). The minimum scaled passing score (MSPS) is 70.

What are the CHWS eligibility requirements?

Eligibility requires dialysis water experience: 3 years with a high school diploma, 2 years with an Associates degree, or 1 year with a Bachelor's degree or current BONENT (CHT/CHBT), NNCO (CCNT/CBNT), or NNCC (CCHT) certification or a healthcare credential. Documentation must be submitted with the application.

What topics are covered on the CHWS exam?

The CHWS exam covers seven domains: Water Quality Standards (15%), Water Treatment Terminology (5%), Basic Water Chemistry (15%), Risks & Hazards of Inadequately Treated Water (15%), Water Purification Equipment (20%), Water System Performance & Monitoring (15%), and Disinfection Strategies (15%). Water Purification Equipment is the largest domain.

How much does the CHWS exam cost?

BONENT exam fees are $235 for paper-and-pencil testing and $255 for computer-based testing in the USA. An optional expedited application fee of $100 is available for faster processing. Annual certification maintenance requires a $65 fee after passing.

What is the AAMI action level for bacteria in dialysis product water?

AAMI/ANSI/ISO 13959 sets the action level for bacteria in hemodialysis product water at <100 CFU/mL and the maximum allowable level at <200 CFU/mL. For dialysate, stricter limits apply: action level <50 CFU/mL and maximum <100 CFU/mL.

How should I prepare for the CHWS exam?

Download and study the official BONENT CHWS Study Guide/Exam Content Outline PDF. Focus on the largest domain (Water Purification Equipment, 20%) covering RO mechanics, carbon EBCT (≥10 min for chloramine), and loop design. Master AAMI/ISO 13959 chemical and microbiological limits, CMS Conditions for Coverage, DPD testing methods, and disinfection verification protocols.