Why is the carpet in my car wet?

A wet footwell is almost never a mystery once you know where cars actually let water in. There are five or six usual suspects and each one has a distinctive pattern of where the water appears.

Safety

What you'll need

• Towels and a wet vacuum
• A torch
• A hosepipe and a helper (optional)
• A dehumidifier (optional)

Step by step

1. Establish where the water actually is.Front footwells, rear footwells, boot well, or under the carpet rather than on it. Lift the carpet and feel the underlay — carpets often feel dry while the felt beneath is soaked.
2. Decide whether it is a leak or condensation.Condensation shows as general dampness and misted windows and follows cold nights. A leak produces a wet patch, usually in one place, and follows rain or a car wash.
3. Check the scuttle drains first.The channel below the windscreen where the wipers sit collects leaves. When the drains block, the water backs up and comes into the footwells or the fusebox area. Clearing them fixes a large share of wet cars.
4. Check the sunroof drains if you have one.A sunroof is designed to let water in and drain it away through four tubes down the pillars. Blocked tubes send water into the headlining and down into the footwells, often on the opposite side to where it entered.
5. Look at the door membranes.Behind each door card is a plastic sheet that directs water down and out through drain holes in the bottom of the door. A torn membrane or blocked drain holes put water straight into the footwell.
6. Check the boot seals and light clusters.Water in the spare wheel well is usually a rear light seal or the tailgate seal. It is common, cheap to fix, and it rusts the boot floor if ignored.
7. Consider the air conditioning drain.A blocked condensate drain sends water that should have dripped under the car into the passenger footwell instead. It appears in warm weather with the air conditioning running, which is a useful clue.
8. Test with a hose and a helper.Someone inside with a torch while you run water gently over one area at a time, starting low and working up. Patience here saves a lot of guessing.
9. Dry it out completely.Lift the carpet and the underlay if you can, use a wet vacuum, then a dehumidifier or a heater with the windows slightly open. Underlay holds an astonishing amount of water and will not dry in place.
10. Check for corrosion and electrics while the carpet is up.Look for rust, and for connectors sitting in the wet. Drying a connector and protecting it now avoids a baffling electrical fault later.
11. Deal with the smell separately.Once dry, treat any residual musty smell with an enzyme cleaner and airing rather than a fragrance.

Tips

• Clear the scuttle of leaves every autumn. It takes five minutes and prevents the most common leak there is.
• Rubber mats hold water underneath them and hide a leak for months. Lift them when you check.
• A car that mists heavily inside every morning usually has water in the carpets, not a heater problem.

Common mistakes

• Drying the carpet without finding the source — The water comes back with the next rain, and each cycle adds more corrosion and more risk to the electrics underneath. Find the leak first, always.
• Leaving the underlay in place while drying — The felt underlay holds water for weeks and cannot dry through a carpet. Lifting it is the difference between a dry car and one that smells damp all winter.

If it doesn't work

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