Confirm which interlock the specification selects (single or electric-pneumatic double), then trace it into the detection drawn in each protected room, the releasing control unit and its power, the nitrogen supply that supervises the piping, and the sequence of operation. Most conflicts sit between the sprinkler sheets and the fire alarm sheets, which are often drawn by different people.
Assemble the review package
Gather the fire protection plans and riser diagram, the fire alarm plans and riser showing the releasing control unit and detectors, the reflected ceiling plans for the protected rooms, the electrical plans for the panel and nitrogen equipment circuits, the sequence of operation or input/output matrix, and the issued Section 21 13 18. Review one protected room from detector to deluge valve before assuming another room with the same name is drawn the same way.
WBDG publishes UFGS 21 13 18: Preaction Sprinkler Systems, Fire Protection as a public guide-specification reference (accessed October 17, 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 |
|---|---|---|
| Interlock type | System Description article + riser diagram + sequence of operation | Does every document describe the same interlock (single or double), and does the valve trim drawn match it? |
| Detection in each protected room | System Actuation article + fire alarm plans + reflected ceiling plans | Is the detector type and count the actuation article calls for drawn in every room the preaction system protects, including above raised floors or ceilings where specified? |
| Releasing control unit | Releasing Control Unit article + fire alarm riser + equipment plan | Is a releasing control unit shown, located, and connected to the building fire alarm system as the section describes? |
| Manual release and annunciation | Manual actuation, annunciator articles + plans | Are manual release stations and annunciators drawn where the specification and the sequence of operation expect them? |
| Nitrogen supervision | Supervisory Nitrogen System article + riser diagram + electrical plans | Are the nitrogen generator, pressure maintenance device, and supervisory switches shown and circuited for each preaction riser? |
| Primary and secondary power | Electric Power and Secondary Power Supply articles + panel schedules | Is the releasing control unit on a dedicated circuit shown on the panel schedule, and does the battery calculation the section requires cover the devices actually drawn? |
| Notification in the protected area | Notification Appliances article + fire alarm plans | Are the horns and visual appliances the section specifies drawn in each protected room and at its entrances? |
| Hydraulic basis and system volume | Hydraulic Design and System Volume Limitations articles + design notes | Are the density, design area, flow test, and any volume or delivery-time basis the section asks for shown for each preaction system? |
Worked example: a double-interlock specification with single-interlock drawings
Illustrative example: the issued Section 21 13 18 selects an electric-pneumatic double-interlock system for a server room. The riser diagram labels the system single interlock, and the fire alarm plan shows one smoke detector circuit in the room with no input from a low-pressure switch on the sprinkler piping.
Ask the fire protection designer which interlock is intended, then align the riser diagram, the fire alarm sequence, and the detector layout with it. Recheck every other room served by preaction valves, since the same template is usually copied across them.
Avoid a false conflict
A preaction valve on the riser diagram does not tell you the release logic. The interlock type lives in the specification and the sequence of operation, and the detection lives on another discipline’s sheets, so check all three together.
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.