Septic Tank Myth Busters

Separating Fact from Fiction

Those of us who work to improve our environment regularly hear myths and misunderstandings regarding the operation of septic tanks and their impact on the environment. 

This section will help you to find the answers to some commonly asked questions about your septic tank and hopefully put these myths to bed once and for all!

Myth No.1

Once installed a septic tank doesn’t need maintenance and never needs emptying 

FALSE!!!

Empty your septic tank and carry out maintenance once per year or in accordance with manufacturer’s guidelines.

The current advice from the Environment Agency is that septic tanks should be emptied once a year although this can be less frequent depending on usage and manufacturers recommendations.

The reason for this frequency of emptying is that modern fully enclosed septic tank units basically settle out solids and offer little opportunity for treatment and reduction in the volume of sludge. This sludge will eventually fill the tank and overtop blocking your drainage field/soakaway and potentially leading to total system failure. 

We often hear the phrase, ‘I haven’t emptied my septic tank for 40 years’. This may be possible because with some older septic tank systems in use, such as brick lined/concrete tanks, are exposed to air and in these circumstances biodegradation of the sludge will occur and you will experience a reduction in sludge volume. However the old BS6297 standard for these types of tanks does specify annual desludging and in any case failing to desludge any system could result in total system failure.

There are a number of aging brick lined septic tanks that seep straight to ground with no drainage field attached. These systems are illegal and are not permitted under the General Binding Rules. The General Binding Rules state that treated sewage discharged to ground must receive prior treatment from a drainage field/soakaway to avoid the risk of groundwater and surface water pollution. 

Myth No.2

You can flush anything down the drain to a septic tank system

FALSE!!!

Overuse of household bleaches and large solid items can interfere with the operation of a septic tank and could lead to total system failure. Use bleaches sparingly and only flush the 3 P’s, pooh, pee and paper.

This is false. Overuse of household bleaches, disinfectants and solids can diminish or eliminate the microbes in the tank and drainage field/soakaway and can increase the risk of system failure. Users should not dispose of milk, paint brush washings, waste wallpaper paste, unused antibiotics, alcohol & home brewing washings, photographic developing chemicals, weed killer or oils via their foul drainage systems.  Similarly hot tubs and swimming pools containing chlorine must not be connected.  

Also as with any sewage system large flushable items have the ability to block pipes and interfere in the operation of the plant. Excess cooking oil or animal fats can cause excess solids retention and choking of the biological treatment in small plants.  Kitchen waste disposal units are not advisable as these cause excess solids to accumulate it primary tanks and hence there is a need for more frequent desludging.

Remember the 3 P’s; only flush Pee, Pooh and Paper into a septic tank. Certain household products can be used safely in moderation so consider using environmental friendly phosphate free household cleaners and use all chemicals sparingly and in small amounts.

Myth No.3

It is ok for rainfall to drain to my septic tank

FALSE!!!

A septic tank system is designed for the volume of sewage produced by a household/s. Additional volumes are more likely to lead to system failure.

Your septic tank system is designed for the volume of sewage produced by a household/s. Any additional volume has the ability to harm the operation of the system by flushing settled solids through the tank or plant and is more likely to lead to system failure by blocking the drainage field/soakaway. Rainwater from large roof areas can also lead to exceeding the discharge limits under the GBR’s. Divert all rainfall drainage to a watercourse or soakaway.

Myth No.4

It’s ok for my septic tank to discharge direct to a watercourse/river  

FALSE!!!

The General Binding Rules prohibit the discharge of septic tank effluent directly to a river. A British Standard drainage field/soakaway must be installed to dispose of the effluent. If you need further advice on this matter please call the Environment Agency on 03708 506 506.

The General Binding Rules clearly prohibit the discharge of septic tank effluent direct to river. Modern septic tanks offer no treatment of the sewage other than settlement of the solids with the remaining liquid portion having the potential to cause serious pollution. The rules require the remaining liquid portion to be treated by a drainage field/soakaway and must not be discharged directly to a watercourse/river. If your septic is arranged in this manner please contact the Environment Agency for advice on 03708 506 506. 

Myth No.5

A dead animal should be added to a septic tank to help it function  

FALSE!!!

Septic tank systems only require human waste to get started.

This is a common misconception. Modern septic tanks do not need to be seeded, i.e. the addition of organic material to your system to help the process work. Septic systems only require human waste to get started. Occasionally biological materials are used to improve poorly performing drainage fields.

Myth No.6

My septic tank will collapse if I empty it

FALSE!!!

Modern septic tanks are designed to British Standards of engineering and should not collapse when emptied

There is some truth to this claim but employing the services of an experienced and registered contractor should reduce the risk of this occurring. On the whole modern septic tanks are designed to British Standards of engineering and should not collapse when emptied. Another problem is poorly installed tanks being emptied in wet conditions and floating out of the ground on a high water table. Using accredited installers will reduce the risk of this problem occurring.

If you have an older brick lined septic tank and it is at risk of collapsing you should consider replacing the tank with a modern system.  Many of these older tanks have been constructed with block walls, sometimes rendered, and the chemicals in the sewage (especially oils/fats) attack the cement and eat away the render, mortar or the blocks themselves.  Repairs may be possible but it is probably best to replace the tank completely with a modern, more resistant type.

Myth No.7

I only need to empty my tank when it smells

FALSE!!!

This could be a costly mistake as by the time your septic tank emits foul odour’s it is often too late. Aim to have your tank emptied once per year and refer to the manufacturers guidelines for further advice on servicing and maintaining your system.

Waiting to empty a septic tank when it smells could be a costly mistake as by the time your septic tank emits foul odours it is often too late. Aim to have your tank emptied once per year and refer to the manufacturers guidelines for further advice on servicing and maintaining your system.

Myth No.8

Anybody can empty my septic tank  

FALSE!!!

Septic tanks should only be emptied by businesses/persons registered with the Environment Agency as a waste carrier. Ask the contractor for a copy of the licence or licence number before engaging their services. A registered waste carrier should also issue you with a waste transfer note which you should retain for your records.

Only businesses/persons registered with the Environment Agency as a waste carrier are permitted to remove and dispose of sludge from your septic tank. Ask your contractor for the waste carrier’s registration number. Use this number to check on the Environment Agency public register of waste carriers website below. Also check that the registration has not expired.
Check Carriers

Worried about your Contractors??

If you have any concerns about your contractor we would advise that you use another contractor and report the incident to the Environment Agency on 0370 850 6506. 

A registered waste carrier will always provide you with waste transfer note which should be retained for your records.

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