You turn the tap on and what comes out is brown, orange or cloudy. It is alarming, and the instinct is to ring somebody immediately.
Before you do, there are two questions that sort almost every case: is it every tap or one tap, and is it the cold side or the hot side? The answers point at completely different causes and completely different people to call.
First, do not use the hot water
This is the one thing worth doing straight away, and almost nobody does it.
If discoloured water is coming into the house, running a hot tap draws that sediment into your hot water cylinder, where it settles and stays. You turn a temporary nuisance in the street main into a permanent one in your own tank.
Leave the hot side alone until the cold runs clear. Hold off on the washing machine as well, because sediment stains fabric and it is a bad day to put a white load on.
Do not shower through it either. Shower heads and hand-held roses have a fine screen in them, and a hose has one at each end. Dirty water drives the sediment straight into those screens, and they are exactly what it gets caught in. The result is a shower that runs weakly or unevenly days later, long after the water has gone clear, and people ring us about the pressure without ever connecting it to the discoloured water the week before.
If your shower has gone weak since an episode of dirty water, that is where to look first. Unscrew the rose, rinse the screen out, and check the screen at the hose ends too. It is usually a five minute fix rather than a plumbing fault, and it is worth trying before anybody books a callout.
Is it every tap, or one tap?
Every tap, cold side, came on suddenly. Almost always something upstream stirring up sediment that normally sits undisturbed in the mains. Work on the network, a hydrant being used nearby, a burst main being repaired, or a sudden change in flow direction will all do it. Your pipes are fine. The water arriving in them is carrying material that was already in the street main.
One tap only. That is that tap or the short run to it, not your supply. Usually the aerator, a filter screen, or debris caught in the fitting.
Only the hot tap. That is your cylinder or the hot pipework, not the street. Sediment and corrosion build up inside an older tank, and once it is there it comes out gradually every time you draw hot water. We inspected a system in Papakura where hot water flow was minimal at every fixture on an old low pressure cylinder, and internal sludge buildup was a large part of it.
Persistent, cold, only in an older house. Old galvanised steel pipe rusts from the inside. If your discolouration never really goes away and the house has original galvanised plumbing, the pipe itself is the source.
What to do when it is the whole house
Run one cold tap and wait.
Pick the tap closest to where the water enters the property, usually an outside tap or the laundry, and run it steadily for ten to twenty minutes. You are flushing the sediment through rather than drawing it around the rest of the house. Check every few minutes and watch it clear from the bottom of a glass.
If it clears, that was it. Run the other cold taps briefly to clear the branches, then go back to normal use, hot water included.
If it does not clear after twenty minutes, or it keeps returning over several days, ring Watercare on 09 442 2222. That is their side of the meter and there is no cost to you for reporting it. A plumber cannot fix a main in the street.
When does it become a plumbing job?
When the problem turns out to be inside your boundary. Three common versions.
Debris that has lodged somewhere. Sediment that arrives during an event does not always leave. At an apartment in Convoy Lane an ensuite shower had poor flow, and when we dismantled the hose and head we found debris buildup restricting it. Cleaning both restored the pressure. Our note at the time was that it may have been a one off, but if it recurred the right steps were flushing the full pipework and fitting a strainer on the main line to stop debris getting in at all.
That job is the common version of this: the complaint was water pressure, and the cause was sediment. Tap aerators collect it the same way, which is why a single tap running weakly after an event is almost always the aerator rather than anything in the wall.
That is the pattern with sediment: the discolouration passes, and what it leaves behind shows up weeks later as a weak shower or a slow tap.
A cylinder full of sludge. Once sediment is in the tank it does not flush out by running taps, and on an old low pressure cylinder it contributes to restricted flow that never quite comes right.
Galvanised pipe at the end of its life. No filter fixes rust generated inside your own pipes. The answer there is re-piping the affected runs.
Is it safe to drink?
Discoloured water from stirred-up sediment is generally considered aesthetically unpleasant rather than unsafe, and Watercare will say the same. That said, we do not tell people to drink water they are uncomfortable with. Run it clear first, and if it will not clear, report it and use something else in the meantime.
Where we would be more careful is water that is discoloured and smells, or water that is discoloured only on the hot side, since hot water is not intended for drinking anyway.
If it keeps happening
Some properties get it repeatedly, usually because of where they sit on the network or because they are on tank supply rather than town water.
The practical fix is filtration at the point the water enters the house rather than at one tap. We installed a three stage whole house system at a property in Kumeū: a 20 micron sediment filter first, then 5 micron carbon, then a 1 micron final stage, on a stainless bracket with the pipework and fittings run to suit. Cartridges get replaced every six to twelve months depending on use and incoming water quality.
That arrangement deals with sediment before it reaches any fixture, any appliance or the cylinder, which is the difference between filtering your drinking water and protecting your plumbing.
If your water keeps coming through dirty, send us a photo of a glass of it and tell us whether it is every tap or one, and hot or cold. That is usually enough to say whether it is yours or Watercare’s.
Common questions
The water is cloudy and white rather than brown. Is that the same thing?
No, and this one is harmless. Cloudy white water that clears from the bottom of the glass upwards within a minute is air, not dirt, usually after work on the line or a change in pressure. Fill a glass and watch it. Sediment settles to the bottom and stays; air rises and disappears. Air needs nothing done about it.
Will this damage my washing machine or dishwasher?
It can, which is why it is worth pausing them rather than running a cycle through discoloured water. Appliances have inlet filters that catch sediment, and once those clog you get poor fill and error codes that look like an appliance fault. If you have run a load during an event and the machine has been slow to fill since, check the inlet screen before calling an appliance technician.
How long does discolouration after mains work usually last?
Typically it clears within an hour or two of flushing a tap, and sometimes it comes and goes for a day or so as the network settles. What is not normal is discolouration that persists for days, returns repeatedly with no obvious cause, or affects only your property while neighbours are clear. Any of those is worth reporting rather than waiting out.
Should I drain my hot water cylinder if sediment got in?
Not as a first step, and not yourself. On a cylinder in reasonable condition it is usually enough to leave it alone and let normal use clear the worst. Where sediment is genuinely affecting flow, a plumber can assess whether draining is worth doing or whether the tank is old enough that replacement is the better answer, which is the conclusion we reached in Papakura.
Is a jug filter enough?
For drinking water, often yes. For the problem described here, no, because a jug only treats what is already in your glass and does nothing for the shower, the cylinder, the washing machine or the dishwasher. If discolouration is a recurring supply issue rather than a taste preference, the filtration has to be at the point of entry to do anything useful.