A septic tank rarely fails overnight — it warns you first. Catching these signs early is the difference between a routine empty and a dug-up drainage field. Here’s what to watch for.

1. Slow drains throughout the house

If sinks, baths and toilets across the house all drain slowly, the problem is likely the tank or the pipe out of it — not a single blocked fixture.

2. Gurgling pipes

Gurgling from drains or toilets means air is struggling past liquid where it shouldn’t be — often a sign the tank is over-full.

3. Bad smells outside

A well-running system shouldn’t smell. Persistent sewage odour around the tank or drainage field suggests it’s not coping.

4. Wet or lush patches over the drainage field

Unusually green, spongy or waterlogged ground above the drainage field means partly-treated effluent is surfacing instead of soaking away — a classic sign of a full tank or a failing field.

5. Sewage backing up

The most urgent sign. If wastewater backs up into the lowest drains or the garden, stop adding water and get it looked at straight away.

6. It’s been over a year

Even with no symptoms, most family tanks need emptying about annually. If you can’t remember the last empty, it’s due. Use our emptying diagnostic for a recommended frequency.

7. A treatment plant alarm

If you have a treatment plant and its alarm sounds, that’s a fault or a full chamber — don’t ignore it.

What to do

If you’re seeing backing up, pooling or an alarm, treat it as urgent. For the milder signs, book an empty and a check of the outlet — very often that’s all it takes. Leaving it risks damaging the drainage field, which is far more expensive to replace than to empty.

Worried about any of these? Book an emptying or a visit or call us.