How to find a leak in a camping mattress, and patch it so it holds

First: is it actually leaking?

Knowing how to find a leak in a camping mattress starts with a question the makers ask first: is it leaking at all? A mattress that's soft in the morning but not flat may just be cold. Therm-a-Rest says that when a pad “is not flat, but not as full as you inflated it before bed, the problem can often be attributed to the loss of air pressure as your mattress cools.” It adds that “this is particularly true if you inflate your mattress by mouth,” because the warm air from your lungs loses pressure as it cools, and a few more breaths fix it.

If it goes flat, treat it as a leak and start the hunt below. One warning from the same page runs the other way: “Always partially deflate your mattress before you leave it in your tent or car for the day. A full mattress can actually burst from the extra pressure if it warms enough in a hot tent or car all day.”

How to find the leak, step by step

GEAR AID, which makes patch kits, calls finding the hole “probably the most time-consuming part” of the job. These steps combine the published instructions of Therm-a-Rest, Sea to Summit, NEMO and GEAR AID, which agree on the method:

1. Inflate it firm. Therm-a-Rest: “Inflate your mattress as firm as you can get it with your breath.”
2. Listen first. If you're lucky, you'll hear it. Therm-a-Rest notes that the sound of air escaping can tip you off “before you've seen any bubbles.”
3. Use soapy water or a dunk. Spray or sponge a film of water and dish soap over the surface, or submerge the mattress. Sea to Summit calls a swimming pool ideal, a sink difficult and a bathtub “a good compromise,” and says to dunk it in roughly 12-inch (30 cm) sections. For a big self-inflating mattress, the soap is the practical choice: Sea to Summit says submerging its Comfort Deluxe is impractical and “wiping the inflated mat with soapy water is the best option.”
4. Raise the pressure. Therm-a-Rest suggests “folding your pad in half to force more air into a section of the pad than your lungs alone can achieve.” Pressing down or sitting on the section you're checking does the same job.
5. Be patient. For a pinhole that takes all night to empty the mattress, Therm-a-Rest says bubbles can take a while to form, “in some cases ten or more minutes.” Work one section at a time.
6. Check both sides and keep going. GEAR AID says to check whether a puncture went all the way through to the other side, and Sea to Summit says to keep testing after the first hole because “there may be multiple points of air loss.”
7. Mark it, then rinse and dry. Sea to Summit and GEAR AID mark the spot with a marker or pen. On a flocked PVC air mattress, SoundAsleep says to use colored tape instead: “Do not use a pen or marker or you could permanently stain the fabric.” Rinse off the soap before you patch; Sea to Summit wants the surface “free of soap/detergent before continuing.”

Check the valve

If the fabric passes, test the valve. Sea to Summit says to submerge just the valve end, keep it under “for at least 30 seconds,” and watch the valve hinge, because “an air bubble may take around 15 seconds to form.” What you do next depends on who made the mattress:

• Therm-a-Rest sells a do-it-yourself WingLock Valve Repair Kit (the BaseCamp uses a WingLock valve) and a Classic valve kit. Its TwinLock valve, used on the MondoKing 3D and NeoLoft, has no kit: Therm-a-Rest's warranty and repair team handles those.
• Sea to Summit, for its own valves, suggests wiping the valve clean, filming the contact surfaces with petroleum jelly for 24 hours, then wiping it off. If bubbles persist, “replacing the valve insert may resolve the issue”; contact it.
• Napier lists a replacement valve, plug and cap for its Sportz truck-bed air mattress.
• Exped and NEMO list no replacement valve for the mattresses we cover. Exped repairs mats in its own workshops, and NEMO handles spare parts and repairs by request.

How to patch the leak

The makers' instructions differ in materials and cure times but agree on the sequence. Where your mattress came with a kit, its instructions win over anything general, including these.

1. Dry it completely. NEMO: “Allow the pad to dry completely before repairing; this may take overnight.” Big Agnes adds that the pad “should be warm and dry before affixing the patch.”
2. Deflate it fully and lay it on a clean, flat surface with the fabric unwrinkled under the repair.
3. Clean the spot with isopropyl alcohol. Therm-a-Rest says patch jobs “fail most often due to poor surface prep” and to clean “one-inch diameter around the puncture at the very least.” Use a little: “Isopropyl alcohol in excess can damage and weaken the fabrics,” but a wipe or a paper towel's worth is safe.
4. Apply the adhesive. Therm-a-Rest's key point: “it's the glue that does the actual sealing, not the patch.” NEMO spreads adhesive at least one inch past the hole on all sides; GEAR AID's Aquaseal FD instructions say at least half an inch.
5. Cut and place the patch. NEMO says to cut “a rounded patch (no sharp corners)” that covers the hole plus an inch of fabric all round, then smooth it down edge to edge. Sea to Summit smooths from the center outward to push out air pockets.
6. Weight it. Therm-a-Rest calls a weighted press essential for adhesives that take hours to cure, and says adhesive squeezing out from under the patch “is a good thing.” Put a towel between the patch and the weight so the glue doesn't bond to your books.
7. Let it cure, then test it overnight. Cure times are in the table below. NEMO's check: inflate the pad, put “a heavy weight (like your packed bag) on top of it,” and leave it overnight. Therm-a-Rest suggests testing that a repaired pad holds air a few days before a trip.

Where a maker's own figures disagree, as Therm-a-Rest's do, patch in the evening and leave it overnight.

Knit tops, flocked PVC and big air beds

The steps above cover most rips in plain shell fabric. Three kinds of surface need their own approach.

Stretch-knit tops

Several of the thick foam mattresses in our registry have a knit top. Therm-a-Rest's Instant Field Repair Kit “works on all current Therm-a-Rest sleeping pads, except pads with knit fabric: MondoKing, LuxuryMap, Trail Pro.” Its Permanent Home Repair Kit is “compatible with all Therm-a-Rest sleeping pads” and is the one it recommends for larger tears. Sea to Summit repairs the Comfort Deluxe's knit top with silicone adhesive alone for holes under 1/8 inch (3 mm), and with silicone plus the kit's mesh for holes up to 3/4 inch (20 mm).

Flocked PVC air mattresses

SoundAsleep, which makes PVC air mattresses, says its patch kit “does not work particularly well on the top of the mattress because the material is flocked for comfort,” nor on the seams. For those spots it recommends a PVC glue, used to the glue maker's instructions, and it says to focus the leak hunt on the seams.

Big air beds

GEAR AID warns that its Tenacious Tape patches “alone may not be strong enough to hold the amount of PSI (pounds per square inch)” in a large inflatable bed, and uses its Aquaseal FD adhesive for those repairs. A light sleeping pad can take a tape patch by itself. If you're still choosing between a tall air bed and a foam mattress, our self-inflating vs air mattress comparison covers what a puncture costs you with each.

When to send it in instead

Stop patching and call the maker if the leak is at a seam or a valve you can't service, if the mattress is losing air from many places (Sea to Summit asks for exactly that case to come through its warranty form), or if it's young enough that the failure could be a defect. Check the warranty before you glue anything. Luno, for one, excludes “unauthorized modifications or repairs” from its 3-year warranty.

Therm-a-Rest's flat repair fee “covers up to 10 punctures at any one time”; past that, it calls the mattress “at the end of its service life.” Send it clean, or it comes back unworked.

How to prevent the next leak

• Keep it clean. Therm-a-Rest says “body oils, bug spray, and sunscreen” can break down the laminates that bond the outer fabric to the inside of a pad, and suggests a camp sheet or sleeping in base layers.
• Let some air out on hot days. A full mattress left in a sunny tent or car can burst, per Therm-a-Rest.
• Store it with the valve open. Sea to Summit says this lets moisture dry out and “prevents undue pressure from possibly deforming the valve.”
• Put something under it. Therm-a-Rest markets its closed-cell Z Lite SOL as an under-layer that adds R 2.0 and “protection from punctures.” On a cot, a pad sits off the ground entirely; our best cot pads rank the ones sized for it.

If it's done: what to look for in the next mattress

Every inflatable can puncture. What changes is what a puncture costs you, and whether the maker helps you fix it. Look for:

• A foam core. A self-inflating mattress still has foam under you when it loses air. An air mattress or air pad doesn't.
• A valve kit and a patch kit you can buy. Therm-a-Rest sells both for WingLock-valve pads like the BaseCamp. Most makers sell only patches, or nothing online.
• A published repair service. Therm-a-Rest, Exped, Sea to Summit and NEMO all repair mattresses, usually for a fee once a puncture is involved.
• A published bottom-fabric denier. Exped, Therm-a-Rest and Sea to Summit publish 75D polyester bases; NEMO publishes no denier for the Roamer, and the PVC air mattresses publish no thickness.
• A warranty longer than the trip. Terms in our registry run from lifetime down to Napier's 30 days. They cover defects rather than punctures, but a long term covers the valve and seam defects a patch can't fix.

Mattresses with repair support

The BaseCamp is a 2-inch pad, not a thick mattress, so it suits a cot or a sleeper who values repairability over cushioning. For a full-thickness mattress, the MondoKing 3D is the top scorer in our best camping mattresses ranking, and the MegaMat is the warmer of the two single mattresses here. If a leak has you rethinking air altogether, cot vs air mattress compares sleeping off the ground with sleeping on air. To start from scratch, read how to choose a camping mattress. Torn chair fabric is a different repair, covered in how to fix a torn camping chair. Every mattress and pad we score is on the camping mattresses hub.