These were originally designed to take toilet water.  Nowadays dishwashers, washing machines and baths use large volumes of water which disturbs the settlement system on which septic tanks are based. 

All active ingredients in soaps and detergents are biodegradable and when used in moderation will not adversely affect the microbial action which is nessesary for a septic tank to work effectively. However septic tanks can:

• cause smells in the local area
• work in reverse if the soakaway is not working properly.  During periods of heavy rain, if the mortar between the bricks is no longer solid, it will allow water to enter the tank which will result in it filling quicker 
• become more expensive to empty

What is a septic tank

Septic tanks usually require desludging once a year dependent on capacity of the tank.  These can be one chamber containing a T piece or two chambers which separate the solids and the liquids forming a crust at the top.  This offers basic treatment of the effluent but an overflow should only go to a soakaway. 

Under no circumstances should there be any discharge to a ditch or watercourse, or a  discharge to land which affects ground water or causes nuisance to neighbouring properties. 

New systems need consent from the  Environment Agency Call 08708 506506.  Ask to speak to the consenting officer to install a soakaway.  This is a land drainage system involving perforated pipes and  pea beach.  Soakaways particularly in the Weald where the ground is often clay can be ineffective.  You should also seek advice from our Building Control team.

General advice:

• Septic tanks should be inspected monthly to check they are working correctly. (The effluent in the outlet from the tank should be free-flowing and clear. The flow in the inlet chamber should also be free-flowing. )
• If it is not free flowing, the tank may need emptying by a licensed contractor. (Some contractors offer annual maintenance contracts at reduced rates. )
• The septic tank should be emptied at least once a year or according to manufacturer's instructions. (It is normally recommended to leave some sludge in the tank to maintain biological activity.) 
• Keep desludging receipts
• Get inlets, outlets and T pipes checked during desludging for fat build up
• Ask the tanker driver to check the T piece has not fallen into the bottom of the tank.  (They often fall off when the mortar fails which holds them in place.  If you don’t have the T-piece, your tank will act as a cesspool.)
• Soakaways can become blocked if the tank is not adequately maintained.
• A high water table can cause them to act in reverse filling up the tank.   (The sediment can block the pores in the soil, making it necessary to replace the drainage field/mound more quickly than would normally be necessary. Occasionally, it can render the site unsuitable for future use as drainage field/mound.)
• Check ventilation

Disused Septic Tanks/Cesspools

Under Section 59 (drainage of building) of the Building Act 1984, where a disused cesspool, septic tank or settlement tank is prejudicial to health or a nuisance the local authority may require either the owner or the occupier to fill or remove the tank or otherwise render it innocuous.