Blog>Expert Advice>How often should you empty a septic tank?
Last updated: 11 March 2025
How often should you empty a septic tank?
Are your drains backed up or is there a bad smell around your septic tank? If so, it might be time to empty the system. Read on to find out how often you should empty a septic tank.
How often should a septic tank be emptied?
As a guide, most septic tanks should be emptied every three - five years.
The following factors determine how often a septic tank needs to be emptied:
Tank size - Tanks with a large capacity will not need to be emptied as frequently as smaller installations
Number of people in the household - The more people using the toilets, showers and bath, the more wastewater there will be. Septic tanks filter and treat wastewater but can only hold a specific volume. If your water usage is high, your home will discharge more waste into the septic tank
Number of appliances - Septic tanks also store wastewater from your dishwasher and washing machine, You may not need your septic tank emptied as often if you do not have these household appliances
There is no one-size-fits-all rule when it comes to emptying a septic tank. Some installations need to be emptied annually but others can take several years to fill up.
Emptying a septic tank too frequently can disrupt the natural buildup of bacteria in the system. This bacteria is needed to breakdown the waste and separate wastewater from the 'sludge' and 'scum'.
Waiting too long to empty your septic tank can cause damage to the environment and put your health at risk.
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Signs of a full septic tank
It is important to know the signs of a full septic tank. An overflowing septic tank can put the health of your family at risk and damage the land surrounding your installation.
These are the signs of a full septic tank:
Gurgling noises coming from the pipes
Slow draining
Foul smells in your home and garden
Pooling surface water
Drain flies
Increase in garden vegetation
Wastewater can not drain efficiently in and out of a full septic tank. Sludge and scum can buildup and stop the normal flow of waste particles inside of the tank.
When there is not enough space available in a septic tank, waste will drain away from your property more slowly than usual. Multiple blocked drains are also an indicator that it is time to empty your septic tank.
Overflowing septic tanks are prone to leaks. You will notice pools of water around your tank if wastewater is leaking out. There may also be an excess of untreated wastewater moving from the tank to the septic drainage field.
As you can imagine, all of this overflowing wastewater can lead to some unpleasant smells!
Have you noticed a surge of vegetation around your tank and drainage field? A full septic tank may be to blame if your land is starting to look more green and luscious than usual.
How to empty a septic tank
Don't ignore the signs of a full septic tank. Failing to empty the tank when it's needed can have a negative impact on your health and the surrounding environment.
Emptying a septic tank is a job that must be left to the professionals. Depending on the size of the tank, it can take 30 minutes or up to three hours for the waste to be removed.
Emptying waste from a septic tank typically involves the following steps:
A waste disposal professional will open the tank and perform a septic tank inspection
If the tank is full, a large tanker vehicle will be positioned next to your installation and a flexible hose will be inserted down into the system
The hose uses a high force of suction to remove waste from inside the septic tank
Not all waste will be removed from the tank. It is common for only the buildup of sludge and scum to be emptied out. Liquid waste is left to make sure bacteria remains inside of the tank
The waste is pumped into the tanker and driven away to be correctly disposed of
Unless you are a qualified waste disposal professional, avoid emptying waste from your septic system yourself. Regulations set out in 2020 made emptying a septic tank yourself a criminal offence.
Updates to the General Binding Rules made in 2020 also mean septic tanks can no longer discharge waste into rivers, streams and other watercourses. It is now a legal requirement for all septic tank waste to be disposed of by a professional.
Cost of hiring a professional waste disposal service
The size of your septic tank system will determine the cost of a professional emptying service.
The average cost of emptying a small septic tank is £175. This price can increase up to £312.50 for an extra large tank.
Emptying a single chamber septic tank costs less than emptying systems featuring multiple chambers.
Take a look at our septic tank emptying cost guide for more information.
Key Takeaways
Most household septic tanks need to be emptied every three - five years
Signs of a full septic tank include bad smells, blocked drains and an increase in vegetation
Emptying a septic tank too often can stop the system from working efficiently
Septic tank waste must be emptied by a professional waste disposal service to comply with current regulations
Professional septic tank emptying services typically cost between £175 -£312.50
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See the tradespeople we've checked and recommend for your job
See the tradespeople we've checked and recommend for your job