Sewage and drainage

Septic tanks take wastewater from your toilet and grey-water from your bathroom, kitchen and laundry. Check your septic tank meets ‘the general binding rules’ on GOV.UK. If your system does not meet the rules, you must apply for a permit on GOV.UK.

We do not empty septic tanks, you'll need to find a private contractor instead. Empty septic tanks annually to prevent a build-up of sludge.

Replacing a septic tank with a new treatment plant

To comply with the general binding rules you may want to replace a septic tank with a new treatment plant. Building regulations class this as building work, so you must make a building control application. 

Septic tanks affected by flood waters 

If floodwaters have affected your property and you have a septic tank system it may also be affected. It's not easy to identify a failed system, but some indicators include:

• a strong odour around the tank and soakaway area
• wastewater overflowing from the tank
• high sludge levels within the septic tank
• sewage flowing up through the toilet and sinks

For composting toilets or other similar systems, contact the manufacturer for specific advice on how flooding may affect these systems.

Immediate actions while there's flooding in your area

Try to stop all non-essential water use and flush toilets as little as possible. Continue to do this until the ground is no longer flooded.

You may need to have your septic tank emptied more frequently until the ground is no longer flooded. However, 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.

Keep away from the septic tank drainage area, as standing water may contain untreated sewage. Avoid doing works until the ground conditions are suitable.

If your septic tank system becomes flooded

If your septic tank and/or soakaway becomes covered with water, try not to use the system and avoid contact with any standing water that may contain sewage. Continue to do this until the flooding stops and make arrangements to have your tank emptied (if your drainage contractor has confirmed emptying the tank will not cause further issues).

If you’ve 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 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.

When safe to do so, inspect the septic tank system for signs of damage and to check if removal of silt or debris is needed. An appropriately qualified contractor may be needed to inspect and take action. Only trained specialists should clean or repair septic tanks because tanks may contain dangerous gases.