Why is my tent leaking, and how do I reproof it?

A flysheet keeps water out by a coating on the inside and a taped or sealed seam. Both age. But most reported tent leaks are not leaks: they are condensation, which forms on the inside of the flysheet overnight and drips, or water tracking through where the inner tent touches the wet fly.

What you'll need

• Seam sealer suited to your fabric
• A spray-on or wash-in tent proofer
• A soft brush and mild soap
• A dry day, or a garage
• A groundsheet or footprint (optional)

Step by step

1. Rule out condensation first.Condensation appears as a fine even film or many small droplets over the whole inner surface of the flysheet, is worst on cold still nights with several people inside, and often forms without any rain at all. A genuine leak appears at a specific point, usually a seam, a zip or a stress point. Getting this wrong means proofing a tent that had nothing wrong with it.
2. Check for touch-through.If the inner tent is pressed against the wet flysheet — by wind, by a badly pitched inner, or by kit stacked against the wall — water wicks straight across. Wet patches directly where the inner touches the fly are this, not a leak. Repitch so the two layers are separated.
3. Find where the water is actually entering.Pitch it in the garden and use a hose on a gentle spray, one section at a time, with someone inside watching. Start at the top and work down. It is worth the hour because it stops you treating the whole tent for a fault in one seam.
4. Clean the tent before treating anything.Cool water, a soft brush and a mild non-detergent soap or a dedicated tech wash. Never use ordinary detergent or fabric conditioner, which strip and contaminate the coating. Let it dry completely.
5. Seal the seams if that is where it comes in.Seams are stitched, which means thousands of needle holes. Most tents have tape over them from the factory; when the tape lifts or perishes, they leak. Apply a seam sealer matched to the fabric — different products for polyurethane-coated polyester and for silicone-coated nylon — along the inside of the seam, working it in and letting it cure fully.
6. Reproof the fabric if water is soaking through rather than beading.Two different things age: the durable water repellent finish on the outside, which makes water bead, and the coating on the inside, which is the actual waterproof layer. A spray-on proofer restores the outer repellency. If the inner coating has failed — visible as flaking, stickiness or a tent that wets through evenly — it is usually the end of the flysheet.
7. Apply proofer to a clean, correctly damp or dry surface.Follow the product: some go on a wet tent, some on a dry one. Pitch the tent, work in sections, do not miss the areas under the guy points, and let it cure fully before packing.
8. Deal with the groundsheet separately.Water coming up is either a failing groundsheet coating, a pinhole, or hydrostatic pressure from pitching in a hollow. A footprint or a plain groundsheet under the tent solves most of it and protects the floor from abrasion, which is what causes pinholes.
9. Patch a hole rather than proofing round it.Self-adhesive repair patches on the inside of the flysheet or the groundsheet, with a matching patch outside for larger tears. Clean and dry the area first and round the corners of the patch.
10. Check the zips and the pole sleeves.Water tracks along a zip and in through the pole sleeve openings. Storm flaps must be positioned over zips, and a proofer applied along the stitching helps.
11. Pitch it properly next time.A taut flysheet sheds water; a slack one holds pools that eventually push through. Guy it out properly and re-tension after rain.
12. Test before you rely on it.Hose it again after treatment, from the top down, before the next trip.

Tips

• Never wash a tent with ordinary detergent or fabric conditioner. Both destroy water repellency and conditioner leaves a wick that draws water through.
• Reproof at the end of the season rather than the night before a trip. Everything needs a full cure.
• Ventilation is the fix for condensation. Open the vents even when it is cold and wet — especially then.

Common mistakes

• Reproofing a tent that is condensing, not leaking — Condensation forms on the inside of the fly from the moisture people breathe out and it drips. Proofing the outside makes no difference, because the water was never coming from outside. Ventilation and separating the inner from the fly are the fix.
• Washing a tent in a machine with detergent — Detergent residue and fabric conditioner both act as wicks and strip the water-repellent finish. A tent washed this way leaks worse afterwards, and the damage is not always reversible.

If it doesn't work

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