How to drive through flood water

With the risk of floods increasing, it’s important to know how to stay safe when travelling in wet conditions.

Written by

Car and technology expert

Last Updated

16 SEPTEMBER 2022

9 min read

Tips for driving through floods and standing water

According to the Environmental Agency, the number one cause of death during flooding is driving through flood water. Just an egg-cupful of water sucked into your car’s engine, it says, could lead to severe damage to your car – leaving you stranded in a dangerous situation. Understand the risks and what you can do if your route is flooded.

1. Find a different route

The best course of action is to try to avoid standing water completely. You should also stay completely clear of any fast-flowing water, especially in spaces where depth can increase quickly.

Your journey might take a little longer than you planned, but you could avoid damage to your vehicle or, worse still, avoid it being swept away.

2. Size up the water

If you have to drive through water, you should make sure that it’s no more than 10cm deep. Most modern cars, except for 4x4s with a high clearance on the road, could start to float in 30cm of water.

It pays to be very cautious – when you factor in waves from other drivers and uneven road surfaces, you could easily find yourself in unexpectedly deep water.

Try stepping out of the car and, if you have them handy, wading through the water in a pair of wellies. Alternatively, you can pick up a stick to try to gauge the depth of the water instead.

But it’s better to be safe than sorry. The Environment Agency’s advice is to ‘never drive through flood water. Turn around and find another route’. And we strongly recommend that you follow this guidance to keep you and your vehicle safe.

3. Let other vehicles pass

However, if you have no choice and have decided to risk it and the water is shallow enough to drive through safely – 10cm or lower – it’s time to look for oncoming vehicles. Vans, lorries and buses will usually cause a bigger wave than smaller cars and they could make water levels dangerously high, so wait for your turn to use the road.

4. Take the high road

Now that you’ve let oncoming vehicles pass, you can take advantage of the full width of the road to drive along its highest point – this is usually away from the kerb and in the middle of the road.

If there isn’t an option to use the middle of the road, try to spot higher sections to stay in shallower water. If you have some local knowledge of the roads, it would certainly help to stay away from large potholes. Remember, all road surfaces aren’t made evenly.

5. Drive slowly and steadily

Aim to drive at 3-4 mph and stick to first or second gear, but don’t change gear once you’re in the water. If you pick up too much speed, you could create a wave that affects other drivers or, even worse, your tyres could aquaplane and lose contact with the road. If this happens, keep your steering wheel straight and gradually take your feet off the accelerator and brake until the aquaplaning stops.

It’s important not to stop your car. Try to keep a consistent speed and your revs high. You can do this in a manual car by slipping out of gear with the clutch and keeping your foot on the accelerator. This will help you to avoid stalling.

In an automatic car, where there isn’t a clutch to slip, try putting the gearbox into first, marked with a number 1, or braking gently with your left foot while using your right foot on the accelerator. Again, this can help to keep your speed low and your revs high. But don’t brake too hard and stop the vehicle.

By moving at all times, you should stop water getting into your exhaust pipe and damaging your car.

6. Test your brakes

Once you’re high and relatively dry, you’ll need to check your brakes work as expected. Increase the gap between you and any vehicle in front, then try pressing on your brakes to see how they respond. Using them a few times should help to dry off any excess water and can give you the chance to see if there are any problems.

Tips for driving in heavy rain

Driving in wet conditions can be hazardous. Follow our tips below to help you stay safe:

Clear your windscreen of any grease or condensation ahead of time to make sure you have a clear view of the road. Keeping your air conditioning on could help stop your windscreen misting up.
Check that your windscreen wipers are clean, work properly and replace the blades if necessary. Some experts recommend so-called aero wipers, particularly for older cars, as these can keep the wiper closer to the windscreen than standard wipers – preventing them lifting off at high speeds and helping them work more effectively.
Check your tyres. Good tread depth can prevent your car from aquaplaning or losing grip on the road. To be legal, your tyres must have tread depth of 1.6mm across the central three-quarters of the tyre around the whole tyre.
Turn on your headlights so other drivers can see you.
Be mindful of longer stopping distances. The time it takes to react to a hazard (thinking distance) and the time it takes to slow your car down after applying the brakes (braking distance) will be considerably longer in wet weather. This is especially important as visibility will be reduced in such conditions.
Keep your distance and remember that driving at the usual speed limit can be dangerous if you don’t leave enough space between you and the vehicle in front.
Slow down to let your tyres grip the road better and to give you time to respond to hazards.
Avoid deep puddles that might cause your car to lose grip or break down.

What should I look out for when driving in flooded conditions?

Water can make it hard to see the road edge and sections of the road might also be damaged. There may also be other hidden hazards such as:

Downed power lines
Raised or missing drain covers
Debris swept along by the water or from a previous accident
Thick mud hidden beneath the surface of the water that could cause you unexpected problems
Contaminated water, which can carry diseases
Other submerged objects.

It’s also wise to look out for other types of road users, such as motorbike riders, cyclists and pedestrians. Remember, it’s not just rude to splash pedestrians using your car – it’s illegal under section 3 of the Road Traffic Act and you could be fined or given penalty points for driving ‘without reasonable consideration for other persons’.

Never ignore or move ‘Road Closed’ signs. They’re put there because the road isn’t safe to be driven on. If you ignore a road closed sign and drive into a hazard, which ruins your car or leads to an accident, you could find that your insurance provider will refuse to pay out.

It’s also worth knowing where your air intake is situated. In some vehicles this can filter into the bumper or to the wheel well, which could be a problem when driving through a flood or ford. Some 4x4 vehicles are equipped with snorkels that allow them to wade through deep water while keeping the air intake at a safe level.

And don’t forget your mobile phone, so if you do get stuck or stranded you could ring for help – particularly if you have breakdown insurance.

How to cross a ford

It’s estimated that there are more than 2,000 fords in the UK, so it’s important to know what to do if you come across one.

There isn’t always a gate or barrier to stop you from driving through a ford when it’s unsafe, so you should weigh up the risk yourself. Some fords have a depth gauge (normally a large vertical measuring stick) if there’s one handy, check that before starting across. If the water is higher than 10cm you should turn around and find a different route. 15cm of flowing water can be enough to sweep you off your feet so try to gauge the water without wading through it.

Even if you’ve driven through the same ford regularly, remember that the depth of water and how fast it’s flowing can vary widely depending on how much it’s rained recently. Just because you’ve made it across once before doesn’t mean you’ll make it every time.

And don’t automatically follow sat nav instructions to cross there – it has no idea what the conditions are like. You need to decide for yourself if it’s the right thing to do.

If the conditions appear safe, choose a low gear and drive slowly and steadily through the ford to avoid creating large waves. Once you’ve made your way through the water, test your brakes as soon as possible.

Is it better to drive fast through water?

No, it’s never a good idea to drive fast through water for two key reasons:

Aquaplaning – your tyres could lose contact with the road, increasing your risk of losing control and being swept away. If you find yourself aquaplaning, don’t slam on the brakes. Instead hold the steering wheel straight, ease off the accelerator until the wheels contact the road again, then let the car slow down naturally to a safe speed to avoid it recurring.
Waves – the faster you drive through water, the greater the size of waves your car might make. The deeper water can get into exhaust pipes or non-watertight areas of your car or other people’s, causing expensive damage.

Frequently asked questions

What should I do if I break down in a flood?

If you break down in a flood stay in your car and phone for help. If you have breakdown cover, you may be able to get towed to a nearby garage.

Restarting the engine or opening the bonnet could make the initial damage much worse.

Will my car insurance cover flood damage?

You’re most likely to be covered for flood damage with fully comprehensive cover. Even so, you should check the terms and conditions of your policy to be sure. Some policies won’t cover you if, for example, you’ve not taken all reasonable steps to avoid your car being damaged – which could potentially include knowingly driving into a flood.

Find out if your car insurance will cover flood damage

How can I avoid driving on flooded roads?

To help you avoid travelling in flooded conditions, you can sign up for flood warnings by phone, text or email. Each of the devolved nations has its own warning system.