After a flood or water damage: cleaning, drying and using EM against odours

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A cellar flooded after a storm, a leak that has soaked a floor, a river that has burst its banks and invaded the ground floor: after the water come the mud, the damp and, very quickly, a persistent smell of silt and mustiness. Effective microorganisms are sometimes used to reduce these odours during the clean-up.

They can help, but only in their proper place, which is right at the very end. Before them come safety, cleaning and, above all, drying. This guide takes you through it step by step, without promising anything EM cannot do.

Safety first

• Electricity: do not switch the power back on in a flooded room until an electrician has checked the installation. Never touch any electrical appliance while standing in water.
• Gas and heating: have the boiler and any gas appliances that got wet checked. Never use a generator, a petrol-powered pump or a fuel-burning heater indoors: carbon monoxide is invisible, odourless and deadly.
• Contaminated water: floodwater is almost always dirty, and sometimes mixed with sewage or hydrocarbons. Wear boots, waterproof gloves, long clothing, goggles and a mask, and wash your hands often.
• Vulnerable people: keep children away from the work area. If you have asthma or allergies, avoid doing the cleaning yourself.
• Tap water: mains water remains safe to use unless your local authority or water supplier advises otherwise. Water from a flooded private well should be considered unfit to drink until it has been tested.

Think about your insurance before throwing anything away

Photograph the rooms, furniture and damaged items before taking them out, and keep the receipts. Report the damage to your insurer as soon as possible: notification deadlines depend on your policy and the rules in your country, so check your contract.

Remove, clean, dry

Remove the water and mud

Remove standing water and then the mud as quickly as possible. Throw away all food that has been in contact with the water, including jars and damaged tins, as well as medicines and toiletries.

Sort the materials

Porous materials that have been soaked generally cannot be saved: carpet, plasterboard, insulation, chipboard, mattresses, cushions, soft toys, books. They stay damp deep inside and become breeding grounds for mould. Hard surfaces, on the other hand, can be cleaned: tiles, concrete, metal, glass, plastic, solid wood.

Clean hard surfaces

Wash them with clean hot water and an all-purpose cleaner, scrubbing with a brush, then rinse. If the water was mixed with sewage, or for items that go in the mouth (crockery, toys), follow the disinfection advice given by your local authority or public health services. EM does not replace this step.

Dry, above all dry

This is the crucial step. Mould takes hold when materials stay wet: ideally, dry them out within 48 hours. Open everything wide, create draughts, use fans and a dehumidifier. A small, inexpensive hygrometer lets you monitor the air humidity: aim for below 50 to 60%.

Key points

After a flood, the order matters: safety, removal, sorting, cleaning, drying. EM only comes in at the end, for odours, and never in place of any of these steps.

Using EM against odours

Once the mud has gone and the surfaces have been washed, a muddy smell may linger in walls, bare floors or corners. This is where EM can be useful, by steering the breakdown of the last organic residues towards fermentation rather than putrefaction.

Dilution

The manufacturer recommends diluting Microferm EM-A Active Solution at between 1 and 10%: in practice, about 1 litre in a watering can holding 10 to 15 litres of non-chlorinated water. Spray it on the surfaces the water reached, after cleaning, and repeat as often as necessary. As with all uses of EM, it is better to apply more often than to increase the dose.

To wash hard surfaces during the clean-up, you can also use EM Clean multi-purpose cleaner, at the dilutions given in our guide Natural cleaning with EM Clean.

Three precautions

• Never straight after bleach. If you have disinfected, rinse with clean water and wait until everything is dry. Bleach destroys microorganisms, and mixing it with an acidic product such as EM releases a toxic gas.
• Spray a fine mist, don't drench. Each application puts a little moisture back into the room: a light misting in a well-ventilated room won't slow the drying. Heavy watering will.
• Use non-chlorinated water for dilution, and only prepare what you will use that day. The other rules are gathered in our guide Getting started with EM.

Emy's tip

Open doors and windows for a good hour after each spraying. Circulating air carries away the moisture you have just added, and there is nothing to be gained by shutting up a damp room.

Let's be honest: the use of EM after a flood is based mainly on users' experience and the manufacturer's advice. No independent study has measured its effect in a flood-damaged home. EM does not make a home sanitary, does not replace disinfection when it is needed, and does not get rid of mould. If the smell persists despite thorough drying, look for material that is still damp or hidden mould. For everyday odours, see also our guide Banishing bad odours with EM.

Mould: when to call in a professional

Despite all your efforts, mould may appear in the following weeks. The signs: a musty, earthy or cellar-like smell, black, green or white patches, wallpaper that bubbles or peels.

• Small patches, covering less than about 1 m²: you can deal with them yourself. Wear a filter mask, gloves and goggles, clean with a detergent, rinse and dry quickly. Throw away any affected porous materials.
• Larger areas, recurring mould, or a vulnerable person in the home: call in a specialist company, and track down the source of the damp.

Mould can cause or worsen coughs, irritation, allergies and asthma. If you have symptoms, see your doctor.

Did you know?

A musty smell is often the first sign of invisible mould, hidden behind furniture, under floor coverings or in wall linings. Your nose detects the problem long before your eyes do.

Garden, vegetable patch and septic tank after a flood

• In the vegetable garden, do not eat any vegetable, fruit or herb that has been submerged or splashed by floodwater, even cooked: the water may have carried sewage, hydrocarbons or other pollutants, and washing is not enough. Pull up these plants and put them in your general waste bin, without composting them. Then let the soil drain before working it again, so as not to compact it. The usual guidelines for caution: wait at least two months before resowing or replanting vegetables, and allow around three months between the water receding and the first harvest, or even four for root vegetables and those that touch the ground. Work with gloves, wash your tools and hands, and leave boots and gardening clothes outside. If in doubt about the nature of the water, check with your local authority.
• The septic tank: a flooded tank can be disrupted or filled with silt. Have it checked, and emptied if necessary, before returning to normal use. No product replaces this inspection, as we explain in our guide Septic tanks, drains and composting toilets.

In summary

After a flood or water damage, the priorities are safety, insurance, removing the water and mud, sorting porous materials, cleaning and, above all, drying quickly, ideally within 48 hours. EM only comes in at the end: one litre of Microferm in a 10 to 15 litre watering can, in fine, repeated sprayings on cleaned surfaces, to reduce muddy odours, never straight after bleach. EM does not make a home sanitary and does not treat mould: beyond about 1 m² of mould, call in a professional.

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