Something off with the hot water? Start here
Hot only, or cold too? Check first
Run the cold alone
Fill a clear glass from the cold tap and look at it against something white. Then do the same with the hot.
Compare the smell
If an odour is there, notice whether it comes from the hot tap only or from both.
Try another tap
Check a second fixture. A single tap with a problem may be a fixture issue rather than the heater.
Note when it started
Sudden changes, changes after the heater sat unused, and slow changes over months point in different directions.
If it is hot only, the water heater is the likely source and the local installers can help. If the cold is affected as well, the change is in the water supply itself. That is a question for your local health department or a qualified water professional, not a water heater technician.
If you smell gas, leave the house straight away and call the gas utility and emergency services from outside.
If a carbon monoxide alarm sounds, leave and call emergency services from outside.
What different colours usually point to
These are the patterns technicians see most often in hot water that differs from the cold. They are starting points for a technician's inspection, not verdicts.
| What you see in the hot | What it often points to at the heater |
|---|---|
| Rust, orange or brown tint | Corrosion inside the tank once the anode is spent, corroded fittings, or iron-rich sediment stirred up from the bottom |
| Black or dark flecks | Material from a breaking-down anode rod, or deposits loosened from inside the tank or fittings |
| White, tan or clear grains and flakes | Mineral scale from the tank or elements, or pieces of a failing plastic dip tube |
| Milky or cloudy water that clears from the bottom up in a glass | Tiny air bubbles, often after work on the system or with pressure changes; typically not a heater fault |
| Discolouration only after the heater sat unused | Water that sat in the tank and fittings, or sediment stirred up when the heater was refilled |
Smells that appear only in the hot water
The most common complaint is a sulphur-like, rotten-egg odour from the hot tap while the cold smells normal. In a water heater, this usually comes from a reaction inside the tank that involves the anode rod and what is in the water. Well water is more prone to it than town water, and it tends to be worse in a tank that sits for a while or runs at a low setting.
The usual approach at the heater is to inspect the anode and, where it makes sense, replace it with a different type. Technicians may also flush the tank. The local installers do not treat water, and they will not tell you anything about what the smell means for the water itself; if the cold smells too, that belongs with a water professional.
A musty or stale smell that appears after a heater has been off, as in a seasonal home, often clears once the tank has been flushed and run normally. The technician can advise when they reopen the heater.
On a private well?
Why well homes see this more
Private wells deliver water with whatever minerals the ground provides, and heating that water brings things out that you would never notice in the cold. Iron can tint hot water and stain fixtures. Minerals settle as sediment and scale. And the anode rod, which protects the tank by corroding in its place, can react with some well water in ways that produce odour. None of this is a judgement on the well; it is what happens when a particular water sits hot in a steel tank.
- Tell us the home is on a well
- Mention any treatment equipment, even if you do not know what it does
- Say whether the change came on suddenly or gradually
The technician will look at the anode, the sediment and the tank.
What to leave alone
- Removing or changing the anode rod yourself; it is often seized, and the job means working on a tank under pressure
- Turning the temperature up or down to "cook off" a smell
- Draining the tank
- Adding anything to the tank or the water supply
The local installers also do not test water, recommend treatment, or comment on whether water is fit for any use. That is deliberately outside a water heater service.
What the technician checks
They confirm the problem is in the hot water only, then look at the tank's age and condition, the anode rod where it can be reached, sediment at the bottom, the dip tube, and the fittings on the hot side. If the tank is corroding from the inside, discoloured water is often the early warning of a leak to come, and they will tell you so. If the cause is the anode or sediment, they explain the options and give you the price before doing anything.
Anode, flush or replacement, priced before work starts.
Common outcomes
- Anode replacement, sometimes with a different type of anode chosen to reduce odour. See anode rod replacement.
- A flush to clear discoloured sediment. See sediment from a well.
- Dip tube replacement where flakes turn out to be plastic.
- Replacement of corroded fittings on the hot side.
- Tank replacement where rust means the tank itself is corroding.
What affects the cost
An anode swap is a modest job when the rod can be reached and removed; low cellar ceilings and seized rods add time, and some situations call for a segmented anode that can be fitted with limited headroom. Flushing costs depend on how much sediment there is. Replacing a tank is a bigger job again, shaped by access and fuel. Every option is priced before work begins.
How long it takes
Diagnosis is part of the visit. Anode changes and flushes are usually done then and there if the parts are on hand. A smell may take a little while to clear after an anode change as the tank refreshes. If the tank needs replacing, that is scheduled as a separate job.
Discoloured and odd-smelling hot water: questions
Why does only my hot water smell like rotten eggs?
In a water heater, a sulphur-like smell from the hot tap only usually comes from a reaction inside the tank that involves the anode rod. It is more common with well water. A technician can inspect the anode and discuss replacing it with a different type, often alongside a flush.
Does rusty hot water mean my tank is failing?
It can. If the anode rod is used up, the steel tank begins to corrode, and rust in the hot water is often the first sign. It can also come from corroded fittings or iron-rich sediment. A technician can check which, and whether a leak is likely to follow.
Both the hot and cold water are discoloured. Can you help?
That points to the water supply rather than the heater, so it is outside what the local installers do. Contact your local health department or a qualified water professional. If the hot water is noticeably worse than the cold, the heater may be adding to it, and a technician can look at that part.
Is it safe to use the water?
We do not advise on water quality or whether water is fit for any use. For that question, contact your local health department or a qualified water professional. The local technicians look only at what the water heater is doing.
What are the small white bits coming out of the hot tap?
They are commonly mineral scale from inside the tank, or pieces of a plastic dip tube that is breaking down. A technician can tell which by looking at them and at the heater, and replace the dip tube or flush the tank as needed.
Why is my hot water cloudy?
If it clears from the bottom of the glass upward within a minute or two, it is usually tiny air bubbles, often after plumbing work or pressure changes. If it stays cloudy or leaves a deposit, mention it when you call so the technician can look at the heater.
Can changing the anode rod stop the smell?
Often it helps a great deal. Swapping to a different type of anode is one of the most common approaches for hot-water-only odour in well homes. Results vary with the water, and the technician will be straight with you about what to expect.
The smell started after we left the house empty. Why?
Water that sits in a tank for weeks can develop an odour, especially with well water. Flushing the tank and running it normally usually clears it. If it persists, the anode may need attention. Our seasonal reopening visits cover this.
Will a new water heater solve it?
If the problem is a corroding tank, yes. If it is a reaction with the anode, a new tank with the same type of anode may develop the same smell. That is why the technician looks at the cause before recommending replacement.
Do you install water treatment to fix it?
No. Treatment systems are outside this service. The local installers deal with what can be done at the water heater: anodes, flushing, dip tubes, fittings and the tank itself.