Lines are not lanes, and the difference is two
A six-lane pool with a line on both sides of every lane carries seven lines. The same pool with the side walls doing the work at the outside carries five. Nobody gets this wrong on the drawing and plenty of people get it wrong on the purchase order, because the word lane is doing two jobs in the same sentence. Decide which arrangement your pool uses before pricing anything, since two lines on a six-lane order is close to a third of the money.
Where the float count comes from
Floats are strung along the cable and each one occupies a fixed length of it, so the count is the made-up length divided by that pitch. Six-inch spacing on a 78 foot made-up line is 156 floats, and it does not matter whether the floats are four inches across or six — the diameter changes the wave-damping and the storage, not the count.
The count matters because lines get repaired float by float. Knowing that a line carries 156 floats, of which 60 are in the two end sections, is what turns a damaged line into a parts order rather than a new line. The end sections are the ones that get destroyed, because that is where the wall is and where every turn happens.
The tensioning allowance, and why it is a field
A lane line is longer than the course it spans. The tensioner takes up cable, the hook and the terminations take up more, and how much depends entirely on the hardware — which is why this page asks rather than assumes. Three feet is a common working figure and it is what the field starts at, but the number that belongs there comes from whoever made the line and the anchors already set in your walls.
Get it wrong short and the line will not reach; get it wrong long and there is slack you cannot take up, which is worse, because a slack lane line does not do the one thing it is for.
Reel capacity is a wound-length problem
A storage reel holds line in layers wound side by side. The number of wraps across is the usable width divided by the float diameter, the number of layers is the space between the drum and the flange divided by the same, and the length per turn is the circumference at the mean wound diameter. Multiply the three and you have a capacity in feet.
The mean diameter is the part that gets skipped. Line on the outer layer is wrapping a much bigger circle than line against the drum, so capacity grows faster than the layer count suggests — going from three layers to five on a 20 inch drum with four-inch floats does not add two-thirds of the capacity, it adds more, because the added layers are the long ones.
Handling, and the thing to name out loud
A lane line under tension stores energy along its whole length. When a tensioner, hook, anchor or cable lets go, it goes somewhere, and people have been hurt by hardware coming off a wall. Tensioning, anchoring and inspection follow the instructions of whoever made the line and the practice of your facility, and there is no procedure for any of it here.
Weight is the other half of handling. A 78 foot line at 0.55 pounds a foot is 43 pounds of awkward, uncooperative object that wants to go back in the water, and a full set of seven is three hundred pounds moving across a wet deck. Plan the crew rather than discovering the problem at six in the morning.
For the geometry the lines are being set to — lane widths, margins and course length — see the pool lane layout calculator. For how many swimmers those lanes then hold, the swim lane capacity calculator.
Every figure on this page came from you. Lane counts, per-lane loadings, lane widths, course lengths, send-off intervals, spacings and session lengths are fields you fill in from your health department, your facility operator, the governing body you compete under, the event organiser or your coach. The page holds none of them, does not know which apply to you, and nothing it prints is a statement of what any pool, programme, event or competition requires.
Questions people ask
How many lane lines does a six-lane pool need?
Either seven or five, and the pool decides which. If every lane is bounded by a line on both sides, including the outside lanes, the count is lanes plus one. If the side walls bound the outside lanes, it is lanes minus one. Competition pools are usually the first arrangement and recreational lap setups are frequently the second, but that is a description of what is common rather than a rule, and your facility and the body you compete under settle it. The calculator asks because getting it wrong is a two-line error, and lane lines are not a cheap thing to be two out on.
Why is the line longer than the pool?
Because the cable has to reach past the water to whatever tensions it. The tensioner, the hook, the terminations at each end and the anchor all consume cable, and how much depends on the hardware. This page takes the allowance as an input rather than assuming one, and the figure to put in it comes from whoever made the line and from the anchors already in your walls. Ordering to the exact course length gives you a line that will not reach; ordering wildly long gives you slack that cannot be taken up, which defeats the point of the line entirely.
How many floats are on a lane line?
The made-up length divided by how much cable each float occupies. At six inches a float, a 78 foot line carries 156. The number is worth having written down because lines are repaired in parts rather than replaced: when a section gets chewed up against the wall you are ordering floats, not a line. The end sections are the ones that suffer, since every turn happens there, which is also why they are a different colour in the first place. The calculator splits the count into end and mid so the parts order matches the damage.
How many lane lines fit on one storage reel?
It depends on the drum, the flanges and the float diameter, and the calculator works it through: wraps across the drum, layers deep, and the length per turn at the mean wound diameter. A 20 inch drum with 60 inch flanges and 48 inches between them takes twelve wraps across and five layers deep with four-inch floats, which is a little over 600 feet — eight lines of 78 feet. Reels fill up faster than people expect with large-diameter floats, because the float diameter divides into both the width and the depth, so doubling it from four inches to eight cuts this reel from 628 feet to 113.
Is there a safe way to tension a lane line?
There is, and it is not on this page. Tensioning, anchoring and inspecting lane lines follows the instructions of whoever made the line and the practice your facility has established, and no procedure appears here. What is worth naming is why it matters: a tensioned line stores energy along its whole length, and when a hook, anchor or cable fails it releases all of it at once toward whoever is standing at the end. That is a real injury mechanism, not a theoretical one. Anything that looks worn at the terminations is a conversation with the maker, not something to improvise around.