- What the Six "Domains" Actually Are
- The Official Exam Categories Behind the Webinars
- Domain 1: Gathering Information and Interior Drainage
- Domain 2: Vents, Storm, Site Drainage and Cold Water
- Domain 3: Hot Water, Expansion and Backflow
- Domain 4: Pumps, Sustainability and Fire Suppression
- Domain 5: Fuel Gas, Medical Gas and Specifications
- Domain 6: Construction Services and Administration
- Source Conflicts You Should Know About
- Sequencing Your Study Around the Six Areas
- Exam Format and Logistics at a Glance
- Frequently Asked Questions
- The six "domains" are ASPE's 2026 CPD review webinars, not six officially weighted exam sections.
- The Certified in Plumbing Design exam has 100 multiple-choice questions in 210 minutes, open book and remotely proctored.
- ASPE's Q&A allocates roughly 65 of 100 questions to Design, but these are approximate item counts, not percentages.
- Specifications, construction services and administration are tested too, so sizing-only preparation leaves gaps.
What the Six "Domains" Actually Are
Search for the Certified in Plumbing Design (CPD) credential from the American Society of Plumbing Engineers (ASPE) and you will quickly notice that no public document lists "six exam domains with percentage weights." That framing is common in other certification programs, but it does not fit this one. The six content areas covered in this guide come from the structure of ASPE Education's 2026 CPD Review Webinar Series, which is organized as Webinar 1 through Webinar 6. We treat each webinar as a preparation heading, and we call them "domains" here only for convenience.
This distinction matters because candidates often over-invest in the sections that look biggest on a syllabus. The CPD is also not a professional engineering license: it does not confer PE registration, a professional-engineer title, or signing and stamping authority. It is a credential for engineers and designers of plumbing systems. If you are still sorting out the basics, our explainer on what CPD certification is covers the fundamentals, and the CPD requirements guide walks through eligibility.
The Official Exam Categories Behind the Webinars
ASPE's CPD Q&A page describes the exam in a different set of categories than the webinar series. These are the closest thing to a public content outline, and they are worth holding next to the webinar list as you study:
| Exam-Related Category | Approximate Published Question Allocation | What It Covers |
|---|---|---|
| Gathering Information and Administration (combined) | About 11 questions | Project scope, existing conditions, team contacts, authority-having-jurisdiction requirements, utility availability, budget constraints, work plans and schedules, coordination with other design disciplines |
| Design | About 65 questions | Identifying required systems, setting criteria for each system, designing the systems, coordinating them with each other and the building |
| Specifications | About 13 questions | Determining and coordinating specification format with the design, describing systems, coordinating plumbing specifications with other specifications |
| Construction Services | About 11 questions | Reviewing submittals and installations for contract-document compliance, witnessing system tests |
Two cautions apply. First, these are approximate item counts, not percentage weights, and they should not be used to rebuild a weighting model. Second, the combined figure of 11 for Gathering Information and Administration should not be split into two separate numbers; the source does not support that. What the table does tell you is directional: Design is by far the largest published allocation, which is why four of the six webinars lean heavily on system design and sizing.
Domain 1: Gathering Information and Interior Drainage
Webinar 1 opens the series with Gathering Information, Flow in Drains, and Interior (Sewage) Drainage Systems. It is a sensible starting point because every plumbing design begins with understanding the project before a single pipe is sized.
Gathering Information
This maps to the task of identifying scope, existing physical conditions and project-team contacts, then determining what the authority having jurisdiction requires, what utilities are available and what budget limits apply.
- Which code and local amendments govern the project
- What water, sewer, gas and storm connections exist and at what capacity
- How existing conditions constrain routing and fixture placement
Flow in Drains and Interior Drainage
Expect the hydraulic fundamentals of gravity drainage: how fixtures load a system, how pipe size and slope interact, and how branches, stacks and building drains are sized for sewage flow.
- Fixture-unit loading and its role in drain sizing
- Slope, capacity and the relationship between flow and pipe diameter
- Layout decisions that affect cleanouts, offsets and stack arrangement
Because ASPE's published task descriptions fold Gathering Information into a small combined category with Administration, do not let this first webinar convince you that project intake is a major portion of the exam. Its real value is foundational: the drainage hydraulics here underpin everything in Webinar 2.
Domain 2: Vents, Storm, Site Drainage and Cold Water
Webinar 2 is a dense one, covering Sanitary Vent Systems, Storm Drainage, Site Drainage, and Cold Water Sizing. It pairs the second half of the drainage picture with the first pressurized system in the sequence.
Sanitary Vent Systems
Venting protects trap seals and keeps drainage flowing freely. Candidates should be comfortable with how vent sizing relates to drainage loading and developed length.
- Vent types and where each is appropriate
- Sizing logic tied to fixture load and pipe length
- Common arrangements and how they are coordinated with the building
Storm and Site Drainage
These cover rainwater removal from roofs and from the site. Roof drain sizing, leaders, horizontal storm piping and site drainage all depend on rainfall design data and the area being served.
- Relating rainfall intensity and drained area to pipe capacity
- Distinguishing roof drainage from site and surface drainage
- Considering secondary or overflow provisions where the design calls for them
Cold Water Sizing
The shift from gravity to pressurized flow is a real change of mindset. Sizing depends on demand, available pressure, pipe length, fittings and velocity considerations.
- Demand estimation for different fixture mixes
- Pressure budgeting from the service connection to the most remote fixture
- Friction loss and how pipe material and size affect it
This is calculation-heavy territory, and because the exam is open book, the skill that matters most is knowing where to find the governing tables and method quickly and applying them correctly. A tidy, well-tabbed reference set is a genuine advantage, within the policy limits discussed later in this guide.
Domain 3: Hot Water, Expansion and Backflow
Webinar 3 groups Hot Water Sizing, Expansion & Contraction, and Backflow Prevention. Together these address how heated water systems are sized and protected, and how potable supplies are kept safe.
Hot Water Sizing
Hot water design involves heating equipment selection, storage and recovery considerations, and distribution. The reasoning builds directly on the cold water methods from Webinar 2.
- Estimating peak demand and matching it to equipment capability
- Distribution and recirculation concepts that affect delivery performance
- Coordinating water temperature with safety and code requirements
Expansion and Contraction
Piping and water both change dimension and volume with temperature. Designers must accommodate thermal movement in piping and thermal expansion of water in closed systems.
- Why thermal movement requires loops, offsets or expansion devices
- How expansion in a closed system is managed
- Support and guide arrangements that allow controlled movement
Backflow Prevention
Protecting the potable supply from contamination is a core responsibility. Candidates should understand the difference between hazard levels and which preventers or air gaps suit each.
- Cross-connection concepts and hazard classification
- Matching the device type to the degree of hazard
- Installation and accessibility considerations
One note on source consistency: the webinar listing for Webinar 4 elsewhere repeats these same three topics in its embedded description. We follow the top-level overview, which places them here under Webinar 3. More on that below.
Domain 4: Pumps, Sustainability and Fire Suppression
Webinar 4 covers a Practice Exam, Sizing Pumps & Pumped Piping Systems, Sustainable Design, and Fire Suppression. The practice exam is a separately named course activity within the series; it is part of the review class, and it does not stand in for the real 100-question test.
Sizing Pumps and Pumped Piping Systems
Pump selection ties together flow, head and system curves. This is among the more analytical topics in the series.
- Determining required flow and total dynamic head
- Reading a pump curve against a system curve
- Considering suction conditions, and how pumped systems differ from gravity systems
Sustainable Design
Water efficiency, conservation strategies and alternative water sources increasingly shape plumbing design. Expect conceptual questions on how design choices reduce consumption and how they interact with code and health requirements.
- Fixture efficiency and its effect on system loading
- Reuse and alternative-source concepts at an overview level
- Trade-offs between conservation and system performance
Fire Suppression
Fire protection is where plumbing design meets life safety. The topic is part of this webinar under the pinned overview; focus on the plumbing designer's role in water supply and coordination with fire protection requirements.
- Water supply considerations for suppression systems
- Coordination between plumbing and fire protection disciplines
If you are weighing how much effort the calculation-based sections demand, our piece on how hard the CPD exam is gives context on where candidates tend to feel pressure.
Domain 5: Fuel Gas, Medical Gas and Specifications
Webinar 5 contains Practice Exam 2, Fuel Gas Systems, Medical Gas Systems, and Specifications. It stretches from specialty piping systems into the written side of the profession.
Fuel Gas Systems
Gas piping design involves demand determination, pressure considerations and pipe sizing against allowable pressure drop, along with the safety provisions the governing code requires.
- Calculating connected load and selecting a sizing method
- Understanding pressure levels and regulation in the system
- Material, venting and installation requirements at a design level
Medical Gas Systems
Healthcare facilities demand specialized systems with strict requirements. Candidates should understand the categories of gases, system components and why these installations are held to a higher standard.
- Typical gas and vacuum services in healthcare settings
- Source equipment, distribution and zone valving concepts
- Testing and verification as part of the overall process
Specifications
This lines up with the published task of determining and coordinating specification format with the design, describing the systems, and coordinating plumbing specifications with other sections. About 13 questions are allocated to it in ASPE's approximate figures, which is a noticeable chunk for a topic many designers underestimate.
- How specifications and drawings divide and complement each other
- Writing clear descriptions of materials, methods and performance
- Avoiding conflicts with the specifications of other disciplines
Specifications is a common blind spot for designers who spend their days on drawings and calculations. Treat it as its own subject rather than hoping to absorb it from experience.
Domain 6: Construction Services and Administration
Webinar 6 closes the series with Quizzes, Construction Services, and Administration. The quizzes are course activities, not a sample of the live exam.
Construction Services
This is the phase where a design becomes a building. The published tasks center on reviewing submittals and installations for compliance with the contract documents and witnessing system tests, with roughly 11 questions allocated in ASPE's approximate figures.
- Evaluating submittals against specified requirements
- Judging whether an installation matches the contract documents
- Understanding the purpose and witnessing of system tests
Administration
Administration appears in ASPE's published categories combined with Gathering Information. The related tasks involve preparing and monitoring work plans and schedules and coordinating with the other professional design disciplines.
- Planning and tracking design deliverables
- Coordinating with architects and other engineers
Candidates focused on career outcomes often wonder how much this kind of project-level knowledge matters in practice. Our overview of CPD jobs and the analysis of whether the credential is worth it explore that angle without inventing salary numbers the issuer has not published.
Source Conflicts You Should Know About
Honest preparation means knowing where the public information disagrees with itself. Three conflicts are worth flagging:
- Webinar contents differ between listings. The top-level overview assigns Fire Suppression to Webinar 4 and the hot water, expansion and backflow topics to Webinar 3. The embedded descriptions for Webinars 4 and 5 repeat some of those topics in different places. This guide follows the top-level overview and does not move subtopics around.
- Calculator rules are inconsistent. ASPE's CPD Q&A says any calculator is permitted, while ASPE Education's review-class page specifies a nonprogrammable calculator. A review-class instruction cannot settle the live exam rule, so confirm with your candidate instructions.
- Electronic-reference rules are not fully reconciled. The Q&A's electronic reference policy permits approved electronic references, pre-existing personal notes and document search, but prohibits AI assistance, secondary devices and outside help. The older open-book FAQ takes a stricter view of CD-ROMs and similar digital media. Do not treat either as blanket permission or prohibition.
Sequencing Your Study Around the Six Areas
You do not need a generic study system here. You need a sequence that respects how the topics build on one another. Since drainage hydraulics feeds venting and storm design, and cold water methods feed hot water, a front-to-back order mirrors the webinar series for good reason.
Drainage foundations
- Work Webinar 1 material: project intake, flow in drains, interior drainage
- Practice fixture-unit loading and drain sizing by hand
Venting, storm, site, cold water
- Cover Webinar 2 in full; this is calculation-heavy, so budget extra time
- Build your tab-free reference organization as you go
Hot water, expansion, backflow, then pumps and fire
- Study Webinars 3 and 4, linking hot water back to cold water methods
- Work pump-curve problems and review sustainable design concepts
Gas systems, specs, construction, administration
- Cover Webinars 5 and 6, giving Specifications dedicated attention
- Finish with timed practice across all areas
Stretch or compress this to fit your schedule; it is a scaffold, not a requirement. For a broader plan that includes resources and pacing, see the CPD study guide, and keep the CPD cheat sheet handy for quick fact review. You can also test yourself on the main practice test site with independently authored questions. Those questions support knowledge preparation only; they are not actual or recalled ASPE questions and are not an official mock exam.
Exam Format and Logistics at a Glance
| Item | Detail |
|---|---|
| Governing body | American Society of Plumbing Engineers (ASPE) |
| Questions | 100 multiple-choice; scored/unscored split unpublished |
| Time | 3.5 hours (210 minutes) |
| Format | Electronically delivered, remotely proctored, open-book written exam |
| Exam fee | $450 ASPE members; $675 nonmembers (current published amounts) |
| Review webinar series | $300 member / $500 nonmember, a separate course price, not an exam fee |
| Results timing | Six to eight weeks |
| Validity | Two years; renewal through CEUs |
The passing score is a committee- and psychometrician-set cut score, not a published fixed number, and scoring reflects correct answers without a wrong-answer penalty. For more on that, read our passing score guide and the CPD pass rate overview. ASPE reported roughly 51% passing for April 2023 and a preceding average around 61%, but those historical cohorts do not predict current results or your individual outcome.
On scheduling, the 2026 exam has been completed, and the credential has not been retired. ASPE indicates to check in November for 2027 dates, and its Q&A says spring 2027 with dates TBD. No exact 2027 dates are asserted here; our exam dates page tracks updates. For cost planning beyond the exam fee, including recertification, see the CPD certification cost breakdown.
Key Takeaway
Use the six webinars as a study map, but weight your time by the published question allocations: Design is the largest category, while Specifications, Construction Services and the combined Gathering Information/Administration group together still account for a meaningful share. Skipping them is a mistake.
Frequently Asked Questions
No. They are the six webinars in ASPE's 2026 CPD Review Webinar Series, used here as preparation headings. ASPE has not published percentage weights for them, and they are not a complete exam blueprint.
ASPE's Q&A allocates about 65 of the 100 questions to Design, with roughly 13 for Specifications and about 11 each for Construction Services and for Gathering Information plus Administration combined. These are approximate counts, not percentages.
Yes, but with conditions. Bound printed references with annotations inside them are allowed, while loose notes, sticky notes and tabs are not. Electronic references are governed by a separate policy that prohibits AI assistance and secondary devices. Confirm details in your candidate instructions.
No. The CPD is not PE registration and does not confer a professional-engineer title or signing and stamping authority. ASPE's own June 2023 article makes this distinction.
The 2026 exam is complete, and 2027 dates are not yet confirmed; ASPE lists spring 2027 as TBD. Eligibility depends on membership approval or a combination of degree and plumbing-design experience, so review our requirements guide and confirm your specific situation with ASPE.