Homeowners have been been told to brace themselves for further flooding as the Government gave warning that water levels on some parts of the River Thames had not yet reached their peak.

Hilary Benn, the Environment Secretary, said that flooding may be unavoidable in vulnerable areas in Henley, Reading and Marlow, where water levels are expected to peak early today. Windsor does not expect to experience its peak until tomorrow. Mr Benn added: “This emergency is still not over.”

About 30 homes were evacuated last night as fresh flooding engulfed a lowlying area of west Oxford, the Environment Agency said.

The Met Office said that 2mm to 4mm (11½in) of rain was likely today and that more sustained downpours of between 5mm and 10mm across the Thames region could arrive tomorrow. It said that the threat of persistent heavy rain would continue through the weekend.

Six severe flood warnings are still in place – three on the Severn and three on the Thames – while on the Great Ouse there is concern for houses in St Neots, Cambridgeshire.

As the waters start to recede in some areas, those left with flood-ravaged rooms face new dilemmas: the clean-up and the inevitable battle with insurers. Despite the urge to get on with the job, householders were urged to remember that the floodwaters pose a risk to health. Tony Thompson, head of emergency response for the Red Cross, told The Times: “If you even handle floodwater you should disinfect yourself. It should be treated as potentially poisonous.”

The water may have been contaminated with sewage, animal waste and other potential toxins, the Health Protection Agency said.

Although harmful microorganisms in floodwater are generally very diluted and present a low risk, infection dangers can be minimised by wearing protective clothing, such as waterproof boots and gloves, while cleaning up. The agency also advised that any open cuts or sores be kept clean and protected from exposure to floodwater by wearing waterproof plasters.

Parents of infants should be careful about using bottled mineral water to make up baby milk. Some brands contain levels of salts that could harm a developing child, official studies have found. As a general rule, sodium concentrations of less than 20mg per litre are preferable and those containing more than 200 mg per litre should be avoided. There should be labelling on the bottle that will indicate if it is not suitable for making up infant formula. The Department of Health and the National Childbirth Trust already advise mothers to use tap water – boiled and then cooled – to make up bottle feed.

The British Damage Management Association, the certifying authority for recovery and restoration professionals, has issued guidelines for those cleaning up and preparing insurance claims. It said that those whose houses are caught in the flooding should try to stop further damage by using brooms and mops to remove any remaining water or residue. Face masks may be needed.

Piles of rubble and mud could damage the structure of the property if left to stand, so should be moved. Possessions that have not been damaged should be moved to safety.

For items that cannot be washed or dry-cleaned, such as mattresses and upholstered furniture, householders were urged to air dry them in the sun, then spray them thoroughly with a disinfectant and steam-clean all carpeting. Mould can form quickly, so householders were told not to use central heating or appliances to try to dry out the house. Instead, they should open windows and doors.

Walls, floors, and many other surfaces should be cleaned with soap and water and disinfected with a solution of one cup of bleach to five gallons of water. Samples of damaged fabrics and flooring should be kept to use as evidence of the damage caused. Similarly, families were urged to take photographs of the damage to show to insurers, and to keep a log of the state of the house, a list of damaged items and their condition. As the water subsides, people should mark the highest point, and the date at which it was reached, on the wall, the association said. It also told people not to switch on electrical appliances that have been in floodwater unless a competent electrician has checked them.

The Royal Mail has agreed to distribute leaflets containing advice from water companies, and the Red Cross has set up a helpline on 08443 911048.

Survivor’s guide

No electricity?

— Be careful with candles, because of the risk from the naked flame

— If you can get to the shops, buy batteries and torches

— Tune in to a local radio station for the latest news

— Get to a friend’s or relative’s house for a shower, or for washing clothes

Source: Red Cross

No running water?

— Water from a bowser should be boiled for ten minutes and then left to cool, to make it safe to drink

— Avoid using water for anything that is nonvital. Make sure the water you have is not wasted

— For those with babies: if mixing formula milk, use bowser or bottled water after it has been brought to the boil. Alternatively, use formula milk

— Water from washing, bathing, or cooking can be reused to flush toilets

Source: Severn Trent Water

Staying safe

— Do not swim in the flood waters. You don’t know what’s below the surface

— Disinfect yourself if you have been in the water. It is filled with all sorts of germs