Skip to content
Septic Tank Problem blocked soakaway

The top 10 causes of Septic Tank Problems and how to solve them

In this guide, we will be looking at the top 10 warning signs that your Septic Tank has a problem. The 10 most likely causes of these problems & some practical tips to solve them.  We offer a FREE consultation for any Septic Tank Problem. Get in touch with us on 0800 3101092 or via our contact form.


A guide to Septic Tank Problems and the Causes

 Get in contact with us on 0800 3101092  or via our Contact Page
Septic Tank Survey Reviews

Septic Tanks fail and have problems, this is inevitable. As a homeowner, the implications can be daunting and cause a potential headache. Please give us a call and we can help you through it. 

This guide will start by outlining the usual signs that something is not as it should be. The slow flushing toilet combined with obnoxious smells and puddles on your lawn is the beginning of a potential nightmare.

While the signs of septic tank problems are well known and seemingly obvious we have a put a list of the common ones below. It’s likely that initially, the problem signs will be intermittent and usually occurring after a period of heavy rain. Septic Tank problems when it rains are not a feature of a healthy system. Take the warning and get the issue sorted before a repair becomes impossibility. In extreme cases, you may become liable for prosecution if the septic tank is causing pollution or a health risk.

The top 10 warning signs of Septic Tank Problems.

  • Slow flushing or in extreme cases an overflowing toilet.
  • Effluent or liquid surfacing around your septic tank, soakaway or drainage field.
  • If you’re discharging to a watercourse, a slow odorous discharge.
  • Movements in the ground in the vicinity of your system.
  • Horrible smells.
  • Gurgling or overflowing drains.
  • Septic tank problems after it rains
  • Problems with your washing machine, dishwasher, etc.
  • Your tank needs emptying more frequently.
  • Water collecting around your manholes.

The main causes of Septic Tank Problems

The main cause of septic tank issues, problems and failures, for both brick and fiberglass models are due to the drainage field or soakaway failing. Please see our guide on soakaway and drainage field problems. Essentially even if your soakaway was properly installed it only has a finite lifespan, based on a multitude of factors.

The other main cause is poor maintenance. Many people do not regularly empty their tank. You should do this at least annually. While you might feel like a super saver by stretching the emptying times, it will end in tears. Not regularly emptying will destroy your system and likely lead to a complete failure which will require a replacement. You also legally have to have your tank serviced once a year. We can organise the annual emptying and service for you.


How to check if your soakaway or Drainage field is working correctly

Drainage Field or Soakaway failure is the most common cause of Septic Tank problems. There is a really easy check to see if this is the issue. Firstly you need to understand how a Septic Tank works. Think of a Septic Tank as a bathtub where you leave the water running. Eventually, the level of the bathtub reaches the overflow hole. If the overflow can deal with the volume of water entering the bath the level will stay at the base of the overflow. In a Septic Tank, this is mirrored by your T-piece on the outlet, this is effectively your overflow. In a healthy system, the level of wastewater in your Septic Tank will sit at the base of the outlet pipe. Please see the associated “good level” picture which shows a Septic Tank at a good working level. Here you can see that the level of the tank is level with the base of the outlet pipe coming off of the T-Piece.
If when you look in your Septic Tank the level is above the base of the outlet pipe then you know there is an issue with your Soakaway or Drainage Field. The extent of that issue can be seen in the following pictures the first shows a system where the discharge has completely failed. This will likely indicate that you require a new discharge. 
In the third picture you can see the level is above the outlet pipe but the tank is holding a level of sorts, it is just higher than it should be. This is a sign that the discharge is beginning to fail, the water table is high or the surrounding area has begun to become saturated. 
If the system has completely failed then raw discharge will be overflowing at another point in the system, normally at the tank lid or a manhole lid. If the level is high but holding then normally there will not be health and pollution issues but the issue will likely get worse so it is a good time to act.
If upon inspection the level of the discharge is below the outlet then the tank has likely failed. This is of course if the tank has not been recently emptied. The reason for this is that if the tank was structurally sound then the level should always sit at the base of the outlet. Having a level sitting below the outlet means the tank is leaking. The difference in distance form the base of the discharge and the level of the water indicates how bad the leak is. 
Septic Tank at a good working level

Septic Tank at a good working level

Septic Tank Problem Complete Failure

Septic Tank Problem Complete Failure

Septic Tank Intermediate problem

Septic Tank Intermediate problem

The top 10 causes of Septic Tank Problems

1. Soakaway/Drainage Field Failure due to age.

The Soakaway is where your Septic Tank drains to.  If the Soakaway fails, which usually means it becomes blocked then the effluent in your tank has no where to go. Even the best constructed Soakaway will eventually fail, they have a finite life. There are instances when they can be repaired but in most cases, it is delaying the inevitable. This is the most common cause of Septic Tank problems we see. The most common solution is to have a replacement soakaway installed. 

2.Lack of regular septic tank emptying.

As discussed above, you need to get your tank emptied annually at least. If you don’t then it will cost you more in the long run. Essentially the tank works by separating out the solid waste and discharging liquid effluent. If you do not empty regularly then the effluent discharged contains more solids. The solids block piping and can destroy the internal workings of your tank. The biggest problem is in the soakaway which is not designed to take solids. This leads to premature failure.

3. Not complying with regulations on annual servicing.

This seems like common sense and in fact, it is. If you do not look after your tank then it may fail prematurely. It is like servicing your car. Septic Tanks are relatively simple and if an internal part has failed it is likely we will be able to identify this and replace. 

4. Inappropriate soakaway/drainage field installation for the ground type you have.

Your Septic Tank mauy discharge to a soakaway. If the Soakaway is not big enough then the tank cannot discharge enough effluent. This will lead to the system backing up. For example, many installers do not undertake percolation tests so the soakaway may not be big enough. Another common issue is where installers have installed a regular soakaway in heavy clay, the effluent does not soakaway.

5. A poorly installed Soakaway/Drainage field.

As part of any septic tank system, the soakaway/drainage field needs to be located in the top 700mm f your soil. If it is not constant aerobic contact is unlikely. This means the effluent is not being treated and broken down. If the effluent is not broken down it will relatively quickly block the soakaway. The system will then not have anywhere to discharge the effluent to. 

6. The water table rising is another common problem.

Should the water table rises to be level with your soakaway then the effluent cannot escape.

7. Putting items into the system that it cannot handle,

For instance, tampons, condoms and nappies.

8. Damage to the system, particularly the pipework and soakaway.

This can be caused by heavy weight being placed on top of the system. This can collapse or block elements of the system.

9. An increase in the amount of effluent you are putting into your system.

Similarly the system not being able to handle the level of effluent due to poor design. This means that simply there is too much going in.

10.Pipework being blocked;

A common cause is sodium binding driven by excessive or prolonged use of detergents. Another common issue is the ingress of roots into the system. Obviously, grease, oil and fat accumulation can also cause serious blockages. Please do not use chemicals to try and unblock the problem this could seriously damage your system beyond repair.

2020 septic tank legislation changes

Did you know that as of the 1st of January 2020 the rules around the discharge of Septic tank effluent and waste are chaged? This may mean that you need to upgrade your system to a Sewage Treatment Plant. Check out our guide for more details.

Septic Tank Problems & Solutions

As you can see there are various factors that can cause a problem with a septic tank, some are fatal others repairable. If you have a problem get in contact and see if we can help. We would not advise you to carry out any work yourself unless you have experience.

Most common solutions:

  • Repair or replacement of the soakaway element of the septic or sewage treatment system.
  • Identification and unblocking of blocked sections of the pipework within the system
  • Replacement of the Septic Tank with a Sewage Treatment Plant.

Septic tank inspection

Septic tank inspections and servicing are important for existing owners of septic tanks to ensure their system is compliant with the new septic tank rules for which come into force in January 2020, and to highlight any potential faults with the system at an early stage. If there is a problem, these can be hard to identify, get in touch and we can get one of our expert engineers to have a look. An annual service will obviously highlight any problems and prevent problems occurring or getting worse.

Our Core Services

Installation, Replacement, Servicing  & Surveys of Septic Tanks & Sewage Treatment Plants.

Homeseptic Ltd. is rated 4.8 out of 5 based on 28

Our reviews on Google
Google Reviews

New Forest Philosophy

Our company is based in the New Forest Hampshire near the sleepy town of Fordingbridge. All of our engineers grew up in the area with many of us going to school together and being part of the same community. We are all conscious of our environment and share a love of the outdoors. This is why we specialise in environmentally friendly installations with low impact solutions. We operate throughout the south of the UK carrying the ethos of the New Forest with us. 

All of our expert engineers specialise in Septic Tank and Soakaway replacements as well as Sewage Treatment Installations. We are based in the New Forest, Hampshire but operate across the South Coast as well as Wiltshire, Somerset, Devon, Sussex, Surrey, Oxfordshire and Berkshire.


The top 10 Septic Tank Problems and their causes
Article Name
The top 10 Septic Tank Problems and their causes
An overview of the 10 most common septic tank problems. The top 10 causes of these problems and help to solve them.
Publisher Name
Publisher Logo
Call Homeseptic