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Which pipe material is specified by NGWA guidelines and IGSHPA standards as the primary piping for vertical closed-loop ground heat exchangers?

High-density polyethylene (HDPE) SDR-11

Schedule 80 PVC

Copper Type K

Galvanized steel pipe

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2026 Statistics

Key Facts: CVCLD Exam

Exam Questions

NGWA

70%

Passing Score

NGWA

$125

Exam Fee

NGWA

24 months

Experience Required

NGWA

7 CEPs/yr

Annual Renewal CEPs

NGWA

100 psi

Pressure Test Minimum

ASTM F2164

The NGWA CVCLD exam is 75 multiple-choice questions with a 70% passing score ($125 fee, administered by PSI). It tests professional competency in constructing vertical closed-loop geothermal heat exchanger wells including HDPE SDR-11 pipe (PE3408/PE4710, ASTM F714), butt and socket heat fusion, U-bend assembly with weighted insertion, thermally-enhanced bentonite/silica grout (target 0.85–1.6 Btu/hr·ft·°F), ASTM F2164 pressure testing (100 psi, 30 min), propylene glycol antifreeze, EPA UIC Class V classification, IGSHPA C448 standards, loop sizing per ton of capacity, and ANSI/NGWA-01 decommissioning requirements.

Sample CVCLD Practice Questions

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1Which pipe material is specified by NGWA guidelines and IGSHPA standards as the primary piping for vertical closed-loop ground heat exchangers?

A.High-density polyethylene (HDPE) SDR-11

B.Schedule 80 PVC

C.Copper Type K

D.Galvanized steel pipe

Explanation: NGWA guidelines and the ANSI/CSA/IGSHPA C448 standard specify HDPE SDR-11 pipe (PE3408 or PE4710 resin, per ASTM F714) as the required piping material for vertical closed-loop geothermal systems. HDPE is flexible, corrosion-resistant, has excellent thermal properties, and can be heat-fused to create leak-free joints suitable for buried loop installations.

2What does the designation 'SDR-11' mean when applied to HDPE pipe used in closed-loop geothermal systems?

A.The standard dimension ratio, meaning the outside diameter divided by the wall thickness equals 11

B.The pipe has an 11-inch inside diameter

C.The pipe is rated for 11 bar operating pressure

D.The pipe was manufactured to Schedule 11 specifications

Explanation: SDR stands for Standard Dimension Ratio, which is the ratio of the pipe's outside diameter to its wall thickness. An SDR-11 pipe has an OD-to-wall-thickness ratio of 11, giving it a consistent pressure rating regardless of size. For HDPE PE3408/PE4710 at 73°F, SDR-11 yields a pressure rating of 160 psi, which is well above the requirements for closed-loop geothermal systems.

3Which ASTM standard governs the requirements for HDPE pipe (PE3408/PE4710) used in vertical closed-loop geothermal installations?

A.ASTM F714

B.ASTM D2239

C.ASTM F441

D.ASTM D3350

Explanation: ASTM F714 is the Standard Specification for Polyethylene (PE) Plastic Pipe (DR-PR) Based on Outside Diameter, which covers HDPE pipe such as PE3408 and PE4710 in SDR ratings. NGWA loop well guidelines reference ASTM F714 as the applicable standard for the polyethylene pipe used in vertical closed-loop ground heat exchangers.

4What type of heat-fusion joint is formed when two HDPE pipe ends are heated against a flat, heated plate and then pressed together?

A.Butt fusion

B.Socket fusion

C.Electrofusion

D.Saddle fusion

Explanation: Butt fusion is the process of heating the squared, clean ends of two HDPE pipe sections against a flat, temperature-controlled heater plate (typically 400–450°F / 204–232°C), then quickly removing the plate and pressing the melted ends together with controlled fusion pressure. The result is a homogeneous joint with strength equal to or exceeding the pipe itself, making it the preferred method for field joining of loop pipe.

5During a butt fusion joint, what is the purpose of the 'heater removal and pipe joining' step being completed as quickly as possible?

A.To prevent the melt bead from cooling and solidifying before fusion pressure is applied

B.To avoid overheating the pipe beyond its melting point

C.To minimize thermal expansion of the pipe ends

D.To prevent air bubbles from forming in the molten zone

Explanation: The time between removing the heater plate and applying fusion pressure (called 'changeover time') must be minimized because the molten HDPE surfaces begin to cool and oxidize immediately upon exposure to air. If the surfaces cool below their melt temperature before being pressed together, a cold weld or a void can form at the joint interface, significantly reducing joint strength.

6When assembling a U-bend at the bottom of a vertical closed-loop borehole, which fitting configuration is typically used to connect the two legs of the loop?

A.A pre-fabricated HDPE U-bend fitting heat-fused to both down-leg and return-leg pipes

B.A threaded brass elbow connector

C.A mechanical compression coupling

D.A push-fit polybutylene elbow

Explanation: The standard U-bend assembly for vertical closed-loop boreholes uses a pre-fabricated HDPE U-bend fitting (180-degree return bend) that is heat-fused (socket fusion or butt fusion at each end) to the downgoing supply pipe and the return pipe. This creates a monolithic, leak-free connection at the bottom of the borehole before the loop assembly is inserted.

7What is the primary purpose of adding weight or a ballast shoe to the U-bend end of a loop assembly before insertion into a water-filled borehole?

A.To overcome the buoyancy of the water-filled HDPE pipe and allow gravity insertion

B.To provide structural support against borehole wall collapse

C.To pre-tension the pipe against thermal contraction

D.To anchor the pipe to prevent frost heave

Explanation: HDPE pipe filled with water or antifreeze is nearly neutrally buoyant, and empty HDPE pipe is positively buoyant (floats). Adding a weighted insertion shoe or clamp weights at the U-bend end generates enough downward force to overcome buoyancy and allow the loop assembly to sink into the grout-filled or water-filled borehole under gravity. Without ballast, the assembly cannot be inserted to full depth.

8What is the target thermal conductivity range for thermally-enhanced grout used in vertical closed-loop boreholes according to IGSHPA guidelines?

A.0.85–1.6 Btu/hr·ft·°F

B.0.10–0.30 Btu/hr·ft·°F

C.2.5–4.0 Btu/hr·ft·°F

D.0.40–0.60 Btu/hr·ft·°F

Explanation: IGSHPA guidelines specify that thermally-enhanced grout should achieve a thermal conductivity of approximately 0.85–1.6 Btu/hr·ft·°F (1.47–2.77 W/m·K). This is achieved by blending bentonite with silica sand or quartz aggregate, which conducts heat much better than neat bentonite grout (~0.43 Btu/hr·ft·°F) alone. Higher thermal conductivity reduces the effective borehole resistance and shortens required borehole depth.

9Which grouting method places grout from the bottom of the borehole upward, ensuring full annular fill with minimal void formation?

A.Tremie pipe grouting (bottom-up grouting)

B.Top-pour grouting

C.Pressure injection through the borehole casing

D.Gravity fill from a funnel at the surface

Explanation: Tremie pipe (or grout pipe) grouting pumps grout through a small-diameter pipe lowered to the bottom of the borehole, filling the annular space upward as the tremie pipe is gradually withdrawn. This bottom-up method displaces water or drilling fluid upward and out of the borehole, preventing contamination entrapment and ensuring continuous, void-free grout placement — as required by NGWA and state regulations.

10According to ASTM F2164, what are the typical minimum pressure and duration requirements for a hydrostatic pressure test of a completed closed-loop geothermal piping system?

A.100 psi for a minimum of 30 minutes with no pressure drop

B.50 psi for 15 minutes with no pressure drop

C.200 psi for 60 minutes with less than 5% drop

D.150 psi for 45 minutes with less than 2% drop

Explanation: ASTM F2164 (Standard Practice for Field Leak Testing of Polyethylene Pressure Piping Systems Using Hydrostatic Pressure) specifies testing at 1.5 times the system operating pressure, with 100 psi being the widely adopted minimum for geothermal closed-loop systems, held for at least 30 minutes with no observable pressure drop indicating leaks. NGWA loop well guidelines and IGSHPA reference this test as the acceptance criterion before backfilling.

About the CVCLD Exam

Earn the NGWA Certified Vertical Closed Loop Driller (CVCLD) — the national credential for geothermal heat pump well construction. Covers HDPE pipe fusion, thermally-enhanced grouting, pressure testing, and EPA/IGSHPA regulatory compliance.

Questions

75 scored questions

Time Limit

Contact PSI for session time

Passing Score

70%

Exam Fee

$125 (NGWA / PSI)

CVCLD Exam Content Outline

~15%

Pipe Materials & Standards

HDPE SDR-11 pipe (ASTM F714, PE3408/PE4710), identification, handling, UV protection

~15%

Heat Fusion Welding

Butt fusion, socket fusion, joint quality, bead inspection, fusion qualifications

~20%

Loop Assembly & Installation

U-bend assembly, weighted insertion, headers, flushing, commissioning, documentation

~15%

Grouting & Thermal Performance

Thermally-enhanced grout (bentonite + silica), tremie-pipe grouting, thermal conductivity

~10%

Pressure Testing

ASTM F2164 hydrostatic testing (100 psi / 30 min), pre- and post-grout test protocols

~10%

Antifreeze & Heat Transfer Fluids

Propylene glycol, methanol, freeze point, hydrometer/refractometer testing

~10%

System Design & Sizing

Loop length per ton, undisturbed ground temperature, borehole thermal resistance, COP

~5%

Regulatory Compliance

EPA UIC Class V, ANSI/NGWA-01, IGSHPA C448, permits, decommissioning

How to Pass the CVCLD Exam

What You Need to Know

Passing score: 70%
Exam length: 75 questions
Time limit: Contact PSI for session time
Exam fee: $125

Keys to Passing

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

CVCLD Study Tips from Top Performers

1Know butt fusion step-by-step: facing, heating, changeover, joining under pressure, cooling — and what constitutes a rejected joint (asymmetric or flat-spot bead)

2Memorize ASTM F2164 test parameters: 100 psi minimum, 30 minutes, zero pressure drop accepted; hydrostatic only (no pneumatic testing)

3Understand why propylene glycol is preferred: non-toxic, FDA GRAS, biodegradable — methanol is allowed where state regulations permit but is toxic and flammable

4Know that tremie (bottom-up) grouting is required — top-pour is not acceptable for properly sealed boreholes

5Study IGSHPA's 200–300 feet per ton rule of thumb and understand how formation thermal conductivity affects borehole depth

6Review EPA UIC Class V classification: closed-loop geothermal wells are Class V, must not endanger underground sources of drinking water (USDWs)

Frequently Asked Questions

How many questions are on the NGWA CVCLD exam?

The NGWA CVCLD exam has 75 multiple-choice questions administered by PSI at computer-based testing centers. A passing score of 70% (53 correct) is required. The exam is available year-round at 400+ PSI locations nationwide, scheduled at test-takers.psiexams.com/ngwa or by calling (855) 579-4642.

What experience is required to apply for the CVCLD?

Applicants must be at least 20 years old and have 24 consecutive months of experience constructing loop wells or conventional water supply wells. They must also submit two professional references, a Certification Agreement, and a signed affidavit confirming no relevant criminal convictions.

What pipe material does the CVCLD exam test?

The exam focuses on HDPE (high-density polyethylene) SDR-11 pipe — specifically PE3408 and PE4710 resin grades per ASTM F714. Key tested topics include the SDR ratio definition, butt fusion and socket fusion procedures, the ASTM F2164 pressure test (100 psi, 30 min), and proper handling to prevent kinking or UV degradation.

What is thermally-enhanced grout on the CVCLD exam?

Thermally-enhanced grout blends bentonite with silica (quartz) sand to achieve a thermal conductivity of 0.85–1.6 Btu/hr·ft·°F, compared to approximately 0.43 Btu/hr·ft·°F for neat bentonite. It is placed via tremie pipe (bottom-up) to fill the borehole annulus around the loop pipe, reducing borehole thermal resistance and improving system efficiency.

What regulatory standards appear on the CVCLD exam?

Key regulatory topics include: EPA Underground Injection Control (UIC) Class V well classification for closed-loop geothermal systems, ANSI/NGWA-01 (well construction and decommissioning standards), ANSI/CSA/IGSHPA C448 (design and installation standard for ground source heat pump systems), and applicable state permit and well completion report requirements.