Trace each hydronic heating piping run from the drawings into its specified material, valve assignment, and expansion provision, then compare terminal-unit connections and backflow-preventer certification for the same system before treating an isometric as coordinated.
Assemble the review package
Gather the hydronic piping plan or isometric, the terminal-unit schedule (radiators, convectors, unit heaters), the equipment room layout for pumps, expansion tanks, and air separation, the direct-digital-control point list, and the issued low temperature water heating specification. Review one loop or zone completely before assuming a similar-looking run elsewhere carries the same pipe material and valve assignment.
WBDG publishes UFGS 23 21 13.00 20: Low Temperature Water (LTW) Heating System as a public guide-specification reference (accessed September 24, 2026). Use your project’s issued specification and amendments for the actual comparison; the guide specification does not automatically govern your project. The checklist below is an original suggested review workflow, not a reproduction of the UFGS requirements.
Eight checks to run against the issued set
Use one record per location or system. The CSV contains the same eight prompts plus fields for source revisions, observed evidence, the review owner, the decision, and closure references.
| Check | Sources to compare | Question to resolve |
|---|---|---|
| Pipe material and schedule | Isometric material callout + specified steel schedule or copper type | Does the drawn pipe material and schedule or type match the specification for that service, and is Type M copper limited to drain piping rather than used on a supply or return run? |
| Valve type and function | Piping symbol at each location + specified gate, globe, check, balancing, or radiator valve | Does each valve symbol on the drawing resolve to a specific valve type in the specification, consistent with the function (isolation, throttling, balancing) shown at that location? |
| Expansion provision | Long straight-run length and anchor or guide locations + specified expansion-joint type | Where a run is long enough to require expansion accommodation, does the drawing show a loop, offset, or the specified packless bellows or guided slip-tube expansion joint at that location? |
| Terminal-unit valve pairing | Terminal-unit connection detail + radiator valve at inlet and balancing valve at outlet | Does each scheduled radiator, convector, or unit heater show both an inlet control valve and an outlet balancing valve consistent with the specification? |
| Backflow preventer certification | Makeup-water connection + specified reduced-pressure-principle backflow preventer and certification basis | Does the specified backflow preventer make, model, and size appear on the current approved-assembly listing referenced by the specification? |
| Expansion tank and air separation | Equipment room layout + specified tank sizing and connection | Can the specified expansion tank and air-separation tank be traced to the system volume and pump arrangement shown in the equipment room? |
| Controls interface | BAS point list + specified space-temperature control system reference | Are the pump, valve, and terminal-unit control points shown on the drawings consistent with what the referenced control system specification assumes it will receive? |
| Testing and balancing basis | Specified hydrostatic test pressure and flow-measuring device + system commissioning plan | Does the commissioning plan identify the hydrostatic test pressure and the flow-measuring device type (venturi, orifice, or pitot tube) the specification requires for this system? |
Worked example: a supply branch drawn in drain-only pipe
Illustrative example: an isometric shows a heating supply branch to a unit heater labeled as Type M hard-drawn copper, matching the type used elsewhere on the same sheet for condensate drain piping. The specification’s own note restricts Type M copper to drain piping, leaving the supply branch’s intended material undocumented.
Confirm the intended pipe type for the supply branch from the specification’s material table for hot water heating pipe, correct the isometric callout, and back check adjoining branches on the same sheet for the same labeling error before closing the item.
Avoid a false conflict
A pipe material shown correctly on one branch of an isometric does not confirm every branch on the same sheet uses the applicable type; drain, supply, and return piping can share a similar line weight while requiring different copper types or schedules under the specification.
When requirements disagree, follow the project’s document-control and clarification process. Do not assume that drawings always override specifications, or the reverse. Identify the exact sources and request an authorized decision.
Close the issue across the affected documents
Record the location or tag, drawing and specification references, issue dates, observed difference, and the decision needed. Assign an owner and keep the item open until the response identifies the governing requirement. Check the revised drawings and specification references together; a response email alone may leave the issued package inconsistent.
For the overall process, use the guide to drawing and specification conflicts. Mark an inapplicable checklist row with a reason, and distinguish a verified correction from a question that still needs design information.
Where Groundbook fits
Groundbook’s drawing and specification review helps investigate potential disagreements in the documents you supply. Include the relevant specification sections and drawing references, then verify the cited evidence with the responsible reviewers before acting on a finding.