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Protecting Gear During Caving

Why a cave is harder on gear than a storm

Rain is intermittent and falls from above. A cave is continuous, three-dimensional wet: you crawl through it, you kneel in it, and you drag your bag across it. Water arrives as thin mud films that work into zips, folds and buckle mechanisms rather than as a jet you can plan around. Add 100% relative humidity and there is no drying phase during the trip, so anything damp stays damp for six hours.

The second difference is abrasion. Limestone and sandstone in a crawl have edges measured in millimetres, and a bag dragged 200 metres through a muddy passage accumulates more surface damage than a season of kayaking. That is why fabric choice here is an abrasion decision first and a waterproofing decision second, and why the failure mode you should design against is a scored film rather than a failed seam.

The third difference is consequence. Underground, a wet spare layer is a hypothermia risk rather than a discomfort, and a failed headlamp battery is a navigation problem. Cavers carry redundancy for light and for warmth, and a dry bag is the container that makes redundancy possible. The bag itself is cheap; what it protects is not.

What genuinely has to stay dry underground

Sort the kit into three tiers. Tier one is survival: spare batteries, a backup light, a warm insulation layer and a first-aid pouch. Tier two is comfort and food. Tier three is optional survey or photography kit. Only tier one belongs in a welded bag with a rolled closure; tier two can live in a lighter splash-resistant sack; tier three gets a bag only if the trip is dry enough to justify it.

Weights matter more underground than anywhere else because you carry everything through sections where your hands are busy. A tier-one load of 2.4 kg in a 5L welded bag is a realistic minimum for a competent group. Add 1.1 kg of food and you are at the point where two bags split the load better than one, both for squeeze geometry and for the way weight hangs off a harness.

Bag profiles that pass a squeeze

Volume is the wrong first question underground. Profile is. A tall 20L bag with a 26 cm diameter will not pass a 30 cm tight section, while a 10L bag with a 20 cm diameter will, even though the smaller bag holds less. Cavers choose by diameter and length, then check whether the volume that geometry gives them is enough. Slim and long beats wide and short nearly every time.

Note the usable-volume column, which is 15 to 18% below the label once three folds are taken. A 10L bag gives you 8.3 litres, which is exactly the tier-one load plus food for one person. That is why the common caving answer is one 10L bag for the group kit and one 5L personal bag each, rather than a single 20L bag that has to be passed hand to hand through every tight section.

Abrasion: what limestone does to fabric

Drag resistance is a function of film thickness and face fabric together. A 0.3 mm TPU film on a 210D face scores visibly after about 40 metres of muddy crawl, because the film is thin enough that a sharp edge reaches the weave and cuts filaments. A 0.5 mm film on a 420D or 500D face survives several full trips before the surface shows more than polish, and a 0.7 mm film is what we specify for bags that are hauled rather than carried.

Laboratory abrasion testing gives repeatable numbers where a crawl does not, which is why we quote cycles to a standard method rather than metres of passage. The ASTM publishes abrasion test methods for coated fabrics, and a bag maker who can quote cycles to a named method is quoting something you can compare. Field detail on that testing is in our abrasion guide.

Construction detail changes the result as much as thickness. A bag with welded corners rather than folded-and-stitched corners has no thread to abrade, and a bag with the weld on the inside of the base keeps the seam off the rock. Look at where the seams sit before you buy: a seam that runs along the bottom of the bag is a seam you will grind into every crawl.

Mud management and the double-bag rule

Mud is the delivery mechanism for almost every water ingress underground. It packs into the fold line, holds grit against the film and wicks moisture along the closure by capillary action. A bag that is clean and dry on the outside before you roll will seal; the same bag rolled with a film of mud on the fold will seep steadily for hours.

1. Wipe the fold line with a wet hand or a cloth before every roll.
2. Roll away from your body so mud on the outside never touches the inside face.
3. Keep tier-one kit in an inner 2 L pouch inside the 10 L outer bag.
4. Clip muddy bags to the outside of the pack, never inside it.
5. Rinse the closure first when you reach a stream, before you drink or eat.

The double-bag rule is not paranoia, it is a recognition of how closures fail. The outer bag gets muddy and may seep; the inner pouch stays clean because it is only ever opened inside a tent or at the surface. Two seals cost 240 grams and turn a potential hypothermia problem into a wet bag you dry out later.

Closures you can work with numb hands

After two hours in 11 °C water your fingers lose fine dexterity, and a closure that requires pinching a stiff clip becomes genuinely hard to operate. Side-squeeze buckles with a 40 mm webbing tail are the practical answer: they release with a palm press and they can be tightened by pulling the tail with a gloved hand. Small centre-release clips on lightweight bags are the wrong choice underground.

Two rolls instead of three is a reasonable compromise for a bag you open often, provided the bag is carried rather than submerged. Three folds remain the rule for anything that will be hauled through a waterfall or dunked in a sump. Write the rule on the bag if you share kit: a group with mixed habits will otherwise seal the same bag differently every trip.

Cold, water and battery behaviour

Battery capacity falls with temperature, and cavers feel this as a light that dims in the last hour. An alkaline cell at 5 °C delivers noticeably less of its rated capacity than the same cell at 20 °C, and a lithium cell holds up far better in the same conditions. Keep spare cells in an inner pouch close to your body rather than in the outer bag, where they sit in the coldest position on the harness.

Store cells in a rigid container inside the pouch so they cannot be crushed against rock, and never carry loose cells in a pocket where a metal key can bridge the terminals. A shorted cell in a bag is a fire risk that no amount of waterproofing helps with. This is also the argument for keeping the pouch small: fewer items, less chance of contact.

Colour, markings and finding kit in the dark

Visibility underground is a safety feature. A black bag dropped in a muddy passage is genuinely hard to find even with a good headlamp, because wet black film reflects almost nothing. A mint, orange or pale blue bag is visible at 10 metres with a 300 lumen beam, which is the difference between a two-minute search and a lost group kit.

Reflective piping helps when a bag is clipped to the outside of a pack and catches the beam at an angle, but it is not a substitute for a light colour. Mark every bag with a durable code rather than a paper label, since paper labels dissolve in a muddy bag within an hour. Groups running shared kit should colour-code by content: one colour for first aid, another for food, another for group spares.

Lashing and hauling bags on a rope

Anything hauled up a pitch needs hard points rated for the job, and this is where lightweight bags fail. A welded D-ring on a TPU bag takes a 40 mm strap and a shock load without deforming; a sewn webbing loop on a cheap bag can tear at 60 to 80 kg. If a bag will be hauled, check that the load path runs through a welded point and not through a seam.

Haul bags also need a closure that will not invert when the bag swings. Roll the closure down towards the base, tape the fold with a short strip of cloth tape for long hauls, and keep the bag upright with a small weight at the bottom. A bag that swings and inverts on a 20 metre pitch usually arrives with the closure unrolled and the contents spread across the pitch floor.

Water crossings, waterfalls and sumps

Caves put bags under water in ways other activities do not: a waterfall in a vertical descent, a chest-deep canal, or a short sump where the bag is pushed ahead of you. Each is a compression event as much as an immersion event, because the bag is squeezed between rock and body while submerged. That is exactly the condition a coated, stitched bag fails and a welded bag survives.

For planned immersion, aim for IPX7 with a 0.5 mm film or heavier, three folds, and a bag packed to no more than 80% so the film has room to flex. Expel air before the final fold so the bag does not fight you in a narrow passage. If the trip includes a known sump, read the immersion material in our canyoneering packing list, which covers the same problem at higher flow rates.

Carry position and harness balance

Where a bag sits on the body decides how much it slows you down. A 3 kg bag clipped to the back of a harness is stable in a crawl and keeps your hands free, but it adds height that catches on low ceilings. A bag carried in front is easier to monitor and to pass through a squeeze ahead of you, at the cost of blocking your own view of the floor. Most experienced cavers run one bag on the back and one small pouch on a chest strap.

Weight distribution matters in vertical work. A bag that hangs below the seat on a long cowstail swings on every move and bruises the thigh; the same bag clipped short to the harness hip point moves with you and stays out of the rope path. Keep the total hanging load under 4 kg and never clip a bag to the same point as a rack or a descender, where it can be trapped during a changeover.

Inside a crawl the rule is simple: push the bag ahead rather than dragging it beside you, and push it on its side so the weld seam along the base is not the contact surface. Pushing takes more effort for the first 20 minutes and then becomes automatic, and it typically halves the abrasion a bag accumulates over a six-hour trip. Groups should agree the convention before the first tight section rather than improvising underground.

The wash routine after a muddy trip

1. Hose the bag down outside before it dries; dried cave mud is far harder to remove.
2. Open the closure fully and flush the fold line with fresh water at ambient temperature.
3. Turn the bag inside out and wipe the interior with a soft cloth and clean water.
4. Work every buckle through its full travel while wet to push grit out of the mechanism.
5. Dry in shade with the mouth open for at least six hours, then store loosely rolled.
6. Inspect the weld corners and the base before the next trip; that is where scoring starts.

Never use a pressure washer on a welded bag, and never use a solvent to remove mud. High pressure can lift a weld edge, and solvents attack the film and the print in the same pass. Warm water, a soft brush and patience remove everything a cave can deposit, and a bag treated this way lasts far longer than one that is scrubbed hard.

Health matters too. Cave mud and standing water can carry organisms that cause illness, so wash hands and any skin contact thoroughly after a trip and keep drinking water separate from anything that touched the passage. The CDC publishes guidance on water and soil-borne exposure that is worth reading before a first expedition.

Specifying caving bags for a club or a retail range

A club fleet is the hardest test a bag faces: shared kit, mixed handling habits, muddy storage and no owner to notice early wear. Specify 0.5 mm film minimum, 500D face, welded D-rings, side-squeeze buckles, a light colourway and a print that survives washing. Those five lines decide whether a fleet lasts one season or five, and they cost less than 15% more than a light-duty build.

For a retail range, the same spec reads differently on the hang tag: drag distance, wash cycles and closure type are the numbers cavers actually compare. We have built waterproof bags since 2014 in an SGS-verified 4,950 m2 facility with 137 staff across seven production lines, sampling in 6 to 10 working days and bulk in 35 to 50 days.

Start from the current product line for sizes and film options, then match volume to your trip profile with our first-aid kit sizing notes and the rock climbing guide, since vertical work shares the same hauling and abrasion problems. Our roll-top range covers the slim profiles that actually pass a tight section.