Do I need to upgrade my septic tank?

Not every septic tank needs upgrading. The question really comes down to where your tank discharges and whether it meets the general binding rules. This guide helps you work out where you stand.

The key test: does it discharge to a watercourse?

Since January 2020, a septic tank must not discharge directly to a surface water — a stream, river, ditch, canal or similar. This is the most common reason a system needs upgrading.

To find out where yours goes, follow the outlet pipe from the tank:

• if it runs to a drainage field — a spread of perforated pipes that lets the liquid soak into the ground — the system discharges to ground, which is generally allowed where the rules are met;
• if it runs to a ditch, stream or other watercourse, the system discharges to surface water and needs upgrading.

If you cannot tell, a drainage specialist can trace and confirm it with a survey rather than leaving you guessing.

When does a sale force the issue?

Selling the property is a recognised trigger. If your tank discharges to a watercourse, the upgrade question will come up during conveyancing, and buyer and seller usually agree who arranges the work. Sorting it before you market the home gives you more control over how — and by whom — it is done.

What does an upgrade usually involve?

There are two common routes:

1. Install a sewage treatment plant. A treatment plant cleans the effluent to a higher standard before it is discharged, so it can legitimately discharge to a watercourse under the rules. It needs power and periodic servicing.
2. Install or extend a drainage field. If your ground is suitable, redirecting the discharge to ground through a properly designed drainage field can be the answer. A percolation test shows whether the soil will accept it.

Which is right depends on your site — available space, ground conditions, the water table, and how close you are to watercourses or a groundwater source protection zone.

Other reasons to consider an upgrade

Even where a system is allowed to stay, age and condition matter. A tank that is undersized for the household, frequently needs emptying, smells, or backs up may be reaching the end of its life. Upgrading proactively can be cheaper and less stressful than dealing with a failure or a pollution incident.

Get a survey before deciding

The reliable way to know whether you need to upgrade — and which option fits your property — is a site survey and, where ground discharge is being considered, a percolation test. A local specialist can carry these out and explain your options in plain English, with no pressure.