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A mat that goes soft overnight needs a diagnosis before it needs a patch. Start with the valve setting and the conditions in which it was inflated, then look for an actual leak. Patching a guessed location wastes repair material and can make later inspection harder.
Table of Contents
Confirm that air is escaping
Check the closure according to the valve instructions. A change in firmness after warm air cools is not identical to a puncture. Inflate the mat as directed, let it settle in stable conditions and observe whether it continues losing support.
Therm-a-Rest’s leak-finding guidance explains both cooling-related pressure changes and bubble checks for escaping air. Follow the method approved for your mat, including whether a soapy cloth or water test is appropriate. Keep soap and dirty equipment out of natural waterways.
Locate and mark the damage
Work through small sections, including the underside and areas around seams and the valve. Tiny leaks may take time to reveal themselves. Mark the location using a method that will not damage the fabric, then clean and dry the area before applying the repair.
If the leak is at a welded seam, inside the valve assembly or associated with a large bulge, ask the manufacturer about repair options. A simple fabric patch may not address that kind of failure.
Use the correct kit and preparation
The Therm-a-Rest Permanent Home Repair Kit is a model-family repair option to investigate. Check the kit listing on Amazon UK and confirm compatibility with your mat. It is not a universal recommendation for every inflatable product.
Therm-a-Rest’s repair instructions emphasise proper cleaning and adhesive application. Follow the supplied sequence, amount and curing requirements. Do not substitute an instant field-repair procedure for a kit that needs time and pressure to bond.
Test before returning it to the kit bag
After the required cure, inflate the mat normally and inspect the repair. Leave enough time to check whether support is maintained and whether another leak remains. Avoid overinflation as a substitute for a proper test.
Finally, review the likely puncture source: grit in the tent, sharp equipment or an unprotected packing arrangement. Keep the compatible repair kit with the mat and replace used supplies. A sound patch plus better handling is more useful than carrying an almost-empty kit into the next trip.
If bubbles come from the closure, use our sleeping-mat valve leak guide. For a larger mattress that softens after its first inflation, also read the air-bed stretch and cooling checks.
Continue with our camping mattress guide.
Reviewed 10 September 2026. This guide is based on published specifications and guidance.