How a septic tank works
A septic tank is a large underground tank that treats waste from your home. Solids settle at the bottom, while fats float to the top. The liquid in the middle leaves the tank and soaks away, usually through a drainage field.
Bacteria in the tank break down some of the waste. However, the tank still needs emptying, because sludge builds up. A full tank lets solids pass into the drainage field and damage it.
Septic tanks vs package treatment plants
A package treatment plant cleans waste water more fully than a basic septic tank. It uses air and bacteria to treat the water. It also needs power and regular servicing.
Both systems need care. Check your paperwork to see which one you have, since the care steps differ. The maker’s manual gives the details.
The 2020 General Binding Rules
In England, the general binding rules set out what owners of small sewage systems must do. One key change took effect on 1 January 2020. A septic tank must not discharge directly into a ditch, stream or other surface water.
Owners with such a tank had to upgrade or replace it, or connect to a mains sewer. Because the rules have been updated since, check the current guidance on gov.uk. Wales, Scotland and Northern Ireland have their own rules.
How often to desludge
The tank needs emptying before it fills with sludge. How often depends on the size of the tank and how many people use it. Your manual or installer can tell you the right interval.
Use a registered waste carrier to empty the tank. Ask for a receipt, because it shows you have looked after the system. Keep these records in one place.
Signs your septic system is failing
Slow drains, gurgling and bad smells can all be signs. Wet, soggy ground near the drainage field is another. Sewage backing up into the house is a serious warning.
Act quickly if you notice these signs, since a failing system can pollute. Call a specialist for advice. Our guide to soakaways explains related drainage.
What to avoid with a septic tank
Do not flush wipes, nappies or fat. They can clog the tank and the field. Avoid heavy use of strong bleach and disinfectants, because they can harm the bacteria.
Spread out laundry through the week, so the tank is not overloaded. Never let rainwater from roofs flow into the tank. It can wash out the solids.
Annual inspection checklist
Look at the tank cover and any manholes for damage. Check for smells and wet patches on the ground. Make sure the outlet and field are clear.
Record the date of each emptying and service. Review your system once a year, because early checks catch problems. If you need help, you can ask for a free quote on our site.
Related guides and local help
If you want to know more, read Soakaway Problems: Why They Fail and What to Do About It. You can also read 7 Signs Your Restaurant Drain Needs a Maintenance Contract and 10 Hidden Plumbing Problems in Victorian Homes to Look For, because they cover closely related problems.
These guides help too: 5 Warning Signs of Pitch Fibre Pipe Failure to Watch For, Foul Drain vs Surface Water Drain: What Goes Where?, Manhole Cover Replacement: Types, Load Ratings and Costs, Why Drains Smell Worse in Summer and How to Stop It and Landlord Drainage Responsibilities: What UK Landlords Do. Each one explains a related topic in plain English.
Need help near you? Read our drain jetting page first, or see Drain Jetting in Blairgowrie and Drain Jetting in Blaydon. You can also see Blocked Drains in Crofton, since every service page has a free quote form. We pass each request to a local drainage engineer.
