How do I know if my septic tank or treatment plant needs emptying?

Posted by Callum Vallance-Poole, on July 25, 2022.

Once you have installed a septic tank or sewage treatment plant it can usually be left to its own devices to collect your waste and dispose of the wastewater away from your home. However, aside from general checks and maintenance inspections, one thing you do have to remain aware of is its capacity and when it needs to be emptied to avoid a build-up of solid waste. Here we explain more about the tell-tale signs that will indicate you need to empty the system.

Do septic tanks and sewage treatment plants do the same job?

A septic tank and sewage treatment plant both rely on gravity to naturally separate solid waste from liquid waste. The main difference between the two systems is that the effluent isn’t treated inside a septic tank, and it can only be discharged into a drainage field. A sewage treatment plant does treat the waste until it is almost fully cleaned, and it can then be discharged into a watercourse (river or stream etc.).

How often should you empty a septic tank or treatment plant?

Ideally, you should plan to empty your septic tank or treatment plan at least once a year. However, you must bear in mind the size and usage levels of the system, as this could mean it has to be emptied more frequently to ensure you avoid any technical problems. For example, if only one or two people live in a property, the system will not need to be emptied as frequently as one used by 4 or 5 residents. When you have the system installed, this is a good question to ask so you can plan for later in the year.

What are the signs of a full septic tank or treatment plant?

A helpful tip to avoid your system becoming full without being aware of it is to schedule reminders to check the tank every few months after it was last emptied. This will ensure you spot any issues before they develop into larger, costly ones that are more expensive to repair.

Slow drains

A sign that your septic tank or treatment plant needs emptying is when the drains in your home are taking longer than usual to clear. If water in your sink, toilet or bath is filtering slowly down the plughole, it could mean the system is full and needs to be emptied, or there is a clog that has to be cleared away. Rather than calling in a professional, you could use a drain cleaner in the first instance, as this may resolve the problem. If not, contact a company that can empty the tank or plant for you, and this should be enough to fix things.

Bad odours

If bad odours start emitting from the sewage treatment plant or septic tank, there is a good chance it is full or very close to its capacity. There is also a chance there could be a leak, so it’s worth having a look to see what the issue could be. Depending on the position of the tank the smell could also be affecting your neighbours, so it’s important to pay attention to bad odours before they raise any complaints.

Drainage backup

This is linked to the slow drain issue we mentioned above. If the tank is not emptied before it becomes full, because it is connected to your home, when too full it will eventually start to back up into the property. It will usually happen in the lowest drains in the house and will likely need you to call in a professional company to clean things up, which adds to your overall costs. Ideally, you want to address the problem before it gets to this point, but if for some reason you are unable to, seeing the drains backup will be clear proof that the system needs to be emptied.

Pooling water

You may spot pools of water sitting around the system, which is usually a good indication that it needs to be emptied. Of course, it could be due to heavy rainfall, but if it has been relatively dry in recent days and weeks then it’s likely that the tank is overflowing and spilling onto the surrounding area. Even if you can’t spot pooling water, take a closer look at the drainage field, because if there is tree root damage or the piping has collapsed, it will need urgent attention.

Lush lawns

Noticing that your garden lawn is looking particularly lush and vibrant may not seem like a warning sign, especially if you have been working hard on it for the past few months. However, while household wastewater isn’t particularly appealing to humans, plants and flowers can’t get enough of it. They absorb some of the nutrients and nitrates found in the waste (similar to manure) encouraging them to grow and really come to life. If you spot this in patches on the lawn, or out of season, it is worth checking the septic tank or sewage plant system to see if there is a leak.

Can you replace the drainage field?

If you are still having problems with your septic tank or sewage treatment plant after it has been emptied, there is likely a deeper cause that needs to be resolved. There are times when the system fails due to age and this can be the case if there are no signs of damage to the tank, plant, or drainage field.

While there is a ‘general’ amount of time you should expect one of these systems to last, there is no single hard and fast rule. That’s because there are so many factors that influence their performance, including the ground conditions, usage levels and overall maintenance. If the pipework is undamaged, but a professional camera survey reveals there is a lot of water inside or that water is re-entering the system after being emptied, this is usually a sign that it needs to be fully replaced.

Marketing Coordinator - Based at our UK HQ in Banbury, Oxfordshire, Callum is responsible for promoting Water Management Systems, Attenuation Tanks, Treatment Plants, Rainwater Harvesting Systems and more!