How your septic tank may be affected in the event of flooding
Toilets and septic tanks
During flooding, both as a result of groundwater, surface water and overtopping of rivers, sewage systems may become inundated by floodwater and this floodwater may become contaminated by pathogenic organisms. However, infection problems arising from floods in the UK are rare. Despite the rarity of such events it is important to be aware of the small risk.
Raw or partially treated sewage may attract domestic animals, vermin and pests which can create an unpleasant environment (odour and sight), but also could be a risk to public health.
The Environment Agency and Public Health England (PHE) work together. This may include risk assessment of whether significant pollution has been produced by industry or from sewage treatment works and/or additional monitoring of watercourses. Environment Agency monitoring information is shared with PHE as required.
It is important to re-emphasise that washing your hands is the most important way to get rid of harmful bugs. Using warm, clean water and soap, rinsing and and drying hands after going to the toilet, before eating or preparing food, after being in contact with floodwater, sewage or with items that have been in the water is the most effective way of preventing infection. Use cold water to wash if warm is not available. If there is no clean water, use disposable soapy, wet wipes or sanitising gel to carefully clean all parts of your hands and dry them.
What if the toilet can’t be flushed at all because of blockage?
The following options may be available to householders whose toilets cannot be used:
it may be possible and practicable to use the facilities of unaffected family, friends, neighbours, public toilets, local shops, supermarkets and hotels. Chemical toilets may be provided in your area
portable bag in bag products designed for solid and urine waste may be provided in your area. Once used according to manufacturers’ instructions, the waste bag should be placed inside another bag, such as a bin liner, and disposed of in the usual way
If you live in a flood-affected area and floodwaters have affected your property, and have a septic tank system (also known as an onsite wastewater system), this may also be affected.
Wastewater from your home contains sewage from your toilet and grey-water from your bathroom, kitchen and laundry. Wastewater can contain human disease-causing micro- organisms such as bacteria, viruses and parasites. Diseases can be transmitted to humans from wastewater if appropriate measures are not taken although this is very rare if safe hygiene measures are followed. The safe disposal of wastewater is an essential part of protecting your health and the health of others. Ensure children and pets are kept away from wastewater affected areas.
The advice in the Environment Agency note, ‘’Dealing with Septic tanks during flooding’, sets. out advice for members of the public and operators responsible for dealing with septic tanks during flooding, with suggestions for what immediate action can be taken if the septic tank is waterlogged and will not drain30. In addition it sets out other options for action in the short and longer term. It also highlights sources of further information.
How will I know if my septic tank system has been affected?
Septic tank systems typically comprise a concrete, plastic or fibre glass tank. In a functioning system, the solids in the wastewater settle in a primary tank, the wastewater is then discharged through pipes into soil in a designated area on your property often called a soakaway or drainage field.
Failed systems are not easy to identify, however some simple indications may include:
a pungent odour around the tank and land application area
blocked fixtures and wastewater overflowing from the relief point
high sludge levels within the primary tank
sewage flowing up through the toilet and sinks
For septic tanks affected by floodwater – recommended immediate, short and long-term actions are:
While there is general flooding in your area:
while a flood is in progress homeowners are advised to eliminate all non-essential water use and flush toilets as little as possible. Continue to do this until the ground is no longer flooded. The Waterwise website has quick tips on reducing water use in the home
although this is unlikely to be sustainable in the long term, it may be necessary to arrange to have your septic tank emptied and the contents removed by a contractor on a regular basis until the ground is no longer flooded
before having your tank emptied get advice from your drainage contractor as in some circumstances emptying the tank can cause mud or silt to be drawn into the tank or, in extreme cases, result in it lifting out of the ground
. If your septic tank system becomes covered with water:
if the area where your septic tank and/or drainage field is located becomes covered with water, if possible do not use the system at all and avoid contact with any standing water that may contain sewage. Continue to do this until the septic tank and/or drainage field is no longer covered in water and make arrangements to have your tank emptied if the situation allows (see above)
consider hiring temporary portable toilet services
if you see pollution please report it to the Environment Agency incident hotline 0800 80 70 60 (Freephone, 24 hour service) so that a team can investigate and take the appropriate action
Short-term actions are:
ensure there are no surface water or clean water connections to the dirty water system. This will reduce effluent volume. It is usually acceptable to dispose of clean surface water via a drainage field or stream without treatment
keep away from the septic tank drainage area, as standing water/wet ground/ponded water may contain untreated sewage. Avoid doing works until the ground conditions are suitable
if you have put caustic or toxic chemicals in your septic tank in the past, and your system backs up into your cellar, basement or drainage field, be especially careful to protect your eyes, skin and lungs from the fumes
if sewage has backed up into the house clean the area and disinfect the floor. Use a household bleach based detergent (according to manufacturer’s instructions) to disinfect the area thoroughly have your septic tank professionally inspected and serviced if you suspect damage. Only trained specialists should clean or repair septic tanks because tanks may contain dangerous gases
for composting toilets or other similar approved systems, contact the manufacturer for specific advice on how flooding or power outages may affect these systems
Recommended long-term actions are:
consider connecting to the public foul sewer if possible. Your local sewerage undertaker will be able to provide details on applications for this connection
keep your system well maintained, so it is better able to cope in extreme weather
consider more appropriate siting of the septic tank and soakaway, away from areas associated with flooding/waterlogging if available
consider an improved treatment option which can be discharged directly to surface water, removing the need for an infiltration system. For further information please contact the Environment Agency National Customer Contact Centre (NCCC) on 03708 506 506, and visit the Environment Agency website for guidance on environmental permits
After the flooding event:
inspect the septic tank system for signs of damage and to determine if removal of silt or debris is required, then take any actions required. An appropriately qualified contractor may be needed to inspect and take action
where surface water or groundwater flooding results in pollution or amenity problems from septic tanks or package treatment plants serving more than one property, and where these cannot be overcome by repairing or maintaining your existing system, your sewerage undertaker may have a duty to provide a public sewer under s101A, Water Industry Act 1991.
Further information on wastewater treatment systems is available on the British Water website34. The Environment Agency website also has advice on the treatment and disposal of sewage where no foul sewer is available35.
The above information comes from Public Health England’s
Guidance on Recovery from Flooding
Essential information for frontline responders
Here is the link should you require further information on how to deal with the aftermath of flooding and flood damage