De & Co Water Tank Cleaning
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Guide · 5 min read

10 signs your rainwater tank needs cleaning.

Tanks don't ring a bell when they need cleaning. They give you smaller hints first — in the taste, the smell, the pressure, the filter cartridges. Here are the ten signs we see most often, in roughly the order they appear.

1. The water tastes different

This is usually the first thing people notice and the most reliable single indicator. If tank water that used to taste clean now tastes earthier, metallic, slightly sour, or just noticeably off — trust your tongue. Sediment is moving through more than it used to.

2. A musty or sulphur smell from the tap

A faint earthy note is normal in tank water. A pronounced musty smell usually means biofilm on the tank walls. A sulphur / rotten-egg smell almost always means anaerobic bacteria have established in the sludge layer at the bottom. Both are clear signals it's time.

3. Visibly cloudy water

Fill a clear glass at the kitchen tap, hold it up to the light, let it sit on the bench for a minute. Tank water should be clear. Cloudiness, fine particles settling at the bottom of the glass, or a slightly tea-coloured tint all point to sediment making it past the inlet.

4. Filter cartridges blocking up faster

If you're on filtered tank water and the cartridges that used to last six months now last six weeks, the tank is the source. The filter is doing its job, the tank is making it work harder.

5. Water pressure dropping

Pump pulling sediment-heavy water from a low tank can lose pressure. So can a sediment build-up in the pipework downstream of the outlet. If the shower has noticeably less pressure than it did six months ago and nothing on the plumbing side has changed, the tank is worth checking.

6. The pump is short-cycling or making new noises

Sediment getting into a pump shortens its life. New rattling, grinding, or short-cycling (clicking on and off rapidly) often starts when a tank crosses a sediment threshold. Worth catching before the pump fails outright.

7. Tea-coloured marks at the outlet

Open the outlet valve at the base of the tank (or have us do it). If the first cupful of water that comes out is dark and sediment-heavy, the sludge layer is well-established. A normal tank should give you fairly clear water from this outlet most of the way through the year.

8. Visible sludge or slime at the inlet

Take the inlet cover off and have a look. A bit of staining is fine. Visible black sludge, green algae, or a thick slimy biofilm on the inlet pipe? Long overdue.

9. Birds, leaves or insects getting into the tank

If you've found anything in the tank that shouldn't be there — a drowned mouse, leaves, a bird — book a clean and don't drink the water until you have. We'll inspect the inlet, overflow, and lid seals while we're there so it doesn't happen again.

10. You can't remember when it was last cleaned

Easy one. If you bought the house and the previous owner didn't mention it, or if "the last clean" is somewhere in the fog of the last three or four years — it's time. Most tanks benefit from an annual clean, so anything past two years is catching up.

If you've ticked off 3 or more

Don't wait. Sediment-heavy tank water is harder on filters, harder on pumps, and not great to drink. A clean now is cheaper than a pump replacement plus a clean in six months. Call Hank on 021 781 618 with rough details and we'll talk timing and cost.

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