A custom duct quote is only as good as the information behind it. Give a fabricator the ten items below and you’ll get an accurate, buildable price the first time, leave them out and you’ll get a range, a list of questions, or a number that changes at submittal.
Every custom duct system is defined by what moves through it and where it has to fit. Here’s exactly what a fabricator needs, and why each item changes the quote.
1. Application and Type of Exhaust
Start with what the duct is actually for. A laboratory fume-hood manifold, a plating-line scrubber duct, and a woodshop dust-collection branch all carry different velocities, materials, and code obligations.
Tell the fabricator the process, the equipment being served, and whether the stream is gas, vapor, fume, mist, or particulate-laden. Corrosive vapors point toward corrosion-resistant thermoplastic; abrasive dust changes both wall thickness and velocity targets.
What information do I need for a custom PVC duct quote?
At minimum: application, chemical constituents, operating and peak temperature, airflow in CFM, duct diameters and lengths, pressure or vacuum conditions, required fittings, and any drawings or field dimensions you have.
2. Chemicals and Concentrations
List every chemical the duct will see, not just the headline one, with concentrations. Compatibility is concentration- and temperature-dependent, so a chemical PVC shrugs off when cold can be aggressive when hot.
Wet, acidic condensate is often more aggressive than the vapor above it. If condensation is expected, say so, it affects material choice, slope, and drain provisions.
3. Normal and Peak Temperatures
Give both the continuous operating temperature and the worst-case peak, including steam cleaning and process upsets. Standard PVC handles continuous service to about 140°F; CPVC extends that to roughly 200°F. See PVC duct temperature limits for the detail.
Quote to the peak, not the average.
A run that averages 120°F but spikes to 160°F is a CPVC job. Reporting only the average is the most common cause of a re-quote.
4. Required Airflow / CFM
Airflow sets diameter, and diameter drives nearly every downstream cost. Provide the design CFM for the system and, on manifolded systems, for each branch.
If you don’t have a CFM figure yet, provide what you do have, hood sash dimensions and target face velocity, or equipment nameplate data, and the fabricator can work back to it. Our guide to sizing fume-hood exhaust duct walks through that math.
5. Duct Dimensions: Diameter, Length, Gauge / Wall Thickness
Send the geometry the run has to satisfy:
- Diameters for each section and branch
- Total run lengths: including vertical rises
- Wall thickness or schedule: if specified
- Support spacing or available hanger points
- Connection sizes at equipment and stack
If wall thickness isn’t specified, the fabricator will recommend one based on diameter, pressure, temperature, and support spacing.
What specifications does a duct fabricator need?
Material, diameter, wall thickness or schedule, total length, fitting types and quantities, joint method, pressure/vacuum rating, service temperature, and connection details at both ends.
6. Pressure / Vacuum Conditions
State whether the duct runs under positive pressure, negative pressure, or strong vacuum, and give the design static pressure if known. Thermoplastic pressure ratings derate as temperature rises, pressure and temperature must be quoted together, never separately.
Strong vacuum drives collapse resistance, which can mean heavier wall or external reinforcement regardless of the chemistry.
7. Fittings and Equipment Connections
A complete fitting count is where quotes get accurate. Identify the type and quantity of each:
- 45° and 90° elbows, with radius preference
- Tees, laterals, and wyes
- Reducers and increasers
- Blast gates and dampers
- Flanges, couplings, and expansion joints
- Hoods, stacks, and end caps
Elbow choice affects both cost and performance, see 90° vs. 45° elbow pressure loss. Also note how the duct terminates at fans, scrubbers, and collectors: flange pattern, bolt circle, and any transition from round to rectangular.
8. Drawings, Sketches and Field Dimensions
Send whatever you have. A dimensioned sketch on paper beats a verbal description every time; a P&ID, isometric, or plan-and-elevation set is better still.
Useful to include:
- Plan and elevation views
- Overall run lengths and rise heights
- Obstructions and clearances
- Tie-in points and equipment locations
- Field-measured dimensions for retrofits
What should I send a PVC duct fabricator?
A short scope description, the chemical and temperature data, CFM, a dimensioned sketch or drawing, a fitting list, and photos of the tie-in points for retrofit work.
9. Installation Constraints
Fabrication decisions follow installation reality. Tell the fabricator where the system will be installed and how it will get there:
- Indoor, outdoor, or plenum space
- UV exposure for outdoor runs
- Access and rigging limits, door widths, hatch sizes, crane reach
- Maximum practical spool length for transport and handling
- Shutdown windows and phased tie-ins
- Who installs, your crew, a contractor, or PDI
Spool lengths and joint locations are a fabrication choice with a delivery consequence. Flagging access limits early avoids sections that can’t reach their final location.
10. Code / Project Requirements
Finally, identify any specification or code requirements that apply to the installation:
- Applicable fire or building-code references
- Insurer or FM Approvals requirements
- Cleanroom or plenum-space classifications
- Smoke and flame-spread ratings
- Testing, documentation, or certification requirements
- Project schedule and delivery milestones
Where the duct is installed can override thermal and chemical ratings, so bring code in at quote stage rather than at submittal review.
What Happens If You Don’t Have Everything?
You don’t need all ten items to start a conversation, but you should know what a partial package buys you.
With application, rough dimensions, and a description of the exhaust, a fabricator can usually give a budgetary range and tell you which unknowns matter most. A firm, buildable number requires the temperature, chemistry, airflow, and fitting detail.
The quickest path is usually a short call: describe the process, and the fabricator will tell you which of the ten items actually drive your price.
Checklist: How to Request a Quote for Custom PVC Ductwork
How do I request a quote for industrial exhaust ductwork?
Gather the items below and send them in one package:
- Application: process, equipment served, exhaust type
- Chemistry: all constituents with concentrations; note condensation
- Temperature: continuous and peak, including cleaning cycles
- Airflow: total CFM and per-branch CFM
- Dimensions: diameters, run lengths, rise heights
- Wall thickness: schedule if specified, or let the fabricator recommend
- Pressure: positive, negative, or vacuum, with design static pressure
- Fittings: type and quantity of elbows, tees, reducers, gates, dampers
- Connections: flange patterns and equipment interfaces at both ends
- Drawings: sketch, plan/elevation, or field measurements plus photos
- Install constraints: location, access limits, shutdown windows
- Code requirements: fire, insurer, cleanroom, documentation
- Schedule: required delivery date and any phasing
Get a More Accurate Custom Ductwork Quote
An accurate quote protects both sides: it prevents a change order when the real temperature surfaces mid-project, and it lets the fabricator recommend the material that actually fits rather than the safest, most expensive one.
If you have the first ten items, you’ll get a firm number. If you have three, you’ll get a range and a clear list of what to confirm next, which is still a useful place to start.
Have your specs ready?
Send your custom PVC or CPVC ductwork requirements to PDI and we’ll respond with a recommendation and pricing within one business day.
