If an adjustable swim nappy gaps at the legs or feels tight at the waist, change one setting at a time. Start with the front rise adjustment, refasten the waist, then check both leg openings while your child moves. Tightening every snap at once can hide which part of the fit needs attention.
Start here: this guide troubleshoots the settings on a nappy you already own. If you are choosing a size, begin with our swim nappy size guide. Weight is a starting point; the waist, legs and rise still need to fit securely now.
Know which snaps do what
The nine studs on the front of a Sarah-Jane Collection swim nappy adjust its height, also called the rise. The waist studs fasten the wings around your child. These are separate adjustments: a waist that feels loose does not automatically mean the rise must be shortened.
- Shortest rise: fasten the top and bottom front rows together.
- Middle rise: fasten the top and middle front rows together.
- Tallest rise: leave the front rise fully open.
These settings follow our written swim nappy fitting instructions. Other brands can have different snap arrangements, so use the instructions for the actual nappy.
Reset the fit in a clear order
- Lay the clean nappy open and identify the front rise studs. The Sarah-Jane Collection logo sits at the back.
- Choose a rise setting that provides comfortable coverage. Do not force the shortest setting simply because your child is young.
- Position the nappy and fasten the waist studs evenly on both sides, starting with a comfortable secure setting.
- Check each leg separately. Look for obvious gaps, fabric caught awkwardly around the opening, or digging.
- Let your child move their legs, then check again. If the fit changes, undo the fastenings and reposition before changing another setting.
If there is a gap at one or both legs
First check whether the nappy is sitting centrally and the sides are evenly fastened. Reposition it, then reassess. If the rise is very tall for your child, try the next shorter rise setting and refasten the waist. Keep the change only if it improves the leg fit without pulling or restricting movement.
Do not keep tightening the waist to compensate for a nappy that is too large overall. If the smaller settings still leave obvious gaps, compare the current fit with the size guide or contact us before using it for swimming.
If the waist fits but the legs feel tight
Undo the nappy and check whether the rise is pulling the fabric upwards. Try a taller rise, then refasten and assess both legs again. If the elastic still digs in or movement is restricted, the size or cut may no longer suit. A comfortable waist alone is not enough to confirm the whole nappy fits.
If the snaps will not fasten securely
Check that the matching studs are aligned and that fabric is not caught between them. Do not force, modify or glue a damaged fastening. If a stud is cracked, loose or repeatedly comes undone, stop using that nappy and contact us with a photo of the fastening and product details.
When adjustment is no longer the answer
SJC standard swim nappies cover approximately 4.5–12 kg and large options approximately 10–18 kg. In the overlap, fit decides. A nappy at its largest settings that still digs in may need replacing with the next size; a larger nappy that gaps is not useful growing room.
The Blue Whale reusable swim nappy currently has a standard 4.5–12 kg variant. Check the actual variant when browsing our reusable swim nappies because sizes vary by print.
Before the lesson: swim nappies help contain solids; they do not absorb urine or guarantee containment. Follow the venue’s requirements and use our first swimming lesson packing checklist to keep a clean spare and dry change ready.