How to measure your pool for a backstroke flag line

Take the width wall to wall at water level, and take it separately at each end of the pool. A purpose-built competition pool will be consistent. An older community or school pool often is not, and a difference of a few centimetres between the two ends changes nothing about the flag count but does change how the line tensions.

Measure at the water surface rather than at the deck. Coping, gutters and overhanging deck edges can make the deck-to-deck measurement several centimetres wider than the span the line actually crosses.

The flags hang from fixed stanchions, and the line has to span stanchion to stanchion — not wall to wall. If your pool already has stanchions, measure the distance between them and their height above the water surface. Those two figures, not the pool width, determine the finished length of the line.

• Distance between the two stanchions, at each end of the pool
• Height of the attachment point above the water surface
• Distance of the stanchions from the end wall, which should be 5.0 m
• How the line attaches: hook, cleat, eye bolt, or reel

• Deck-to-deck measured instead of water-level span
• Assuming both ends of the pool are identical
• Deriving the width from the lane count on a pool that was never built to competition lane widths
• Forgetting that the line needs slack to reach the stanchion and tie off, beyond the span across the water
• Measuring a pool with a moveable bulkhead in one position and ordering for another

If you are not certain, send us the measurements you have along with a photograph of the existing stanchions. That is usually enough to resolve the ambiguity without a site visit.