On a private well, a rotten-egg smell that comes only from the hot taps usually starts inside the water heater. Bacteria in the water react with the tank's anode rod and produce hydrogen sulphide gas. If the cold water smells too, the source is the well water itself. Around Ballantrae, Kettleby and Musselman Lake both are common, and the first job is working out which one you have. Before any of that, though, make sure the smell is in the water and not in the air.
First, rule out a gas leak
Natural gas and propane have an odour added so leaks can be noticed, and it smells a lot like rotten eggs. Not every road around Ballantrae has natural gas, so many homes there run propane water heaters and furnaces.
- If you smell sulphur in the air near the water heater, furnace, stove or propane tank, and not just when water is running, leave the house.
- Do not switch lights or appliances on or off on your way out.
- From outside, call your gas utility, your propane supplier or 911.
Never try to find or fix a gas leak yourself. If the smell only appears when a tap runs and fades when it stops, it is the water.
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Hot only, or hot and cold? Finding the source
Run cold water into a clean glass, step away from the sink and smell it. Then do the same with hot water.
- Hot only: the water heater is the likely source. Sulphate-reducing bacteria, which are common and usually harmless in groundwater, react with the magnesium anode rod most tanks use and give off hydrogen sulphide. It is often worse after the heater has sat unused, such as after a holiday, or when the thermostat is set low.
- Hot and cold: the gas is in the groundwater itself, or sulphur bacteria are growing in the well or plumbing. It can come and go with the seasons.
- One sink only: it may be the drain rather than the water. A dry trap or a dirty drain can smell when water runs into it.
A sulphur smell is mostly an aesthetic problem, but any sudden change in a well's taste, colour, cloudiness or smell is worth a water test. In Ontario, private well owners can have their water tested for bacteria at no charge. Sample bottles are available through your local public health unit, which for Ballantrae, Kettleby and Whitchurch-Stouffville is York Region Public Health. A test for hydrogen sulphide, iron, hardness and other minerals is a separate lab analysis and is useful before choosing treatment.
What usually fixes it
If the source is the water heater:
- Replacing the anode rod with a different type, such as an aluminum-zinc alloy or a powered anode, often solves it.
- Do not simply remove the anode. It protects the tank from corrosion, and running without one can shorten the tank's life and may void its warranty.
- Flushing and disinfecting the tank can help. Some methods involve high water temperatures or chemicals, so it is a job for a plumber because of the scald risk.
- If the heater is rented, changes to it are the rental company's decision. Check your agreement and call them first.
- If the tank is old or leaking, replacing it is a good moment to look at treatment upstream. Hard, iron-rich groundwater is common here and shortens a tank's life. Our water heater page covers gas, propane and electric options.
If the source is the well water:
- Treatment depends on how strong the smell is and what else is in the water. Options include oxidizing filters, aeration, chlorination followed by carbon filtration, and carbon filters for low levels. A plumber can explain which suits your test results.
- A water softener alone will not remove the smell. Softeners deal with hardness, though some systems combine softening with other treatment.
- Disinfecting the well (shock chlorination) is sometimes recommended for sulphur or iron bacteria. Public health units publish guidance, and work on the well itself may call for a licensed well contractor.
Checklist: what to note before you call
- Hot only, or hot and cold, and which taps.
- When it started, and whether it is worse after the house has sat empty.
- Your water heater: gas, propane or electric, its age from the label, and whether it is owned or rented.
- Any treatment you already have: softener, iron filter, UV or reverse osmosis.
- Recent well test results, if you have them.
- Any staining, such as orange or black marks in sinks and toilets.
When to call a plumber
Call if the smell is only on the hot side and has not cleared after a day of normal use, if it is on both sides and you want treatment, or if it came with other changes such as discolouration, low pressure or a leaking tank. Homes around Kettleby and the rest of King Township, and around Musselman Lake in northern Whitchurch-Stouffville, often have the pressure tank, softener and water heater working together. If the pump is also misbehaving, see our well pressure tank page.
Costs depend on the fix: an anode change is a much smaller job than adding a treatment system, and the right treatment depends on your water test. Ask the plumber to explain the options and what drives each one.
Frequently asked questions
Is water that smells like rotten eggs safe to drink?
The smell itself is usually treated as an aesthetic problem rather than a health one, but it tells you nothing about bacteria. If anything else about the water has changed, test it through public health, and use another supply until you have results.
Why is the smell worse after we have been away?
Water sitting in a warm tank gives the bacteria and the anode time to react, so the first hot water after a trip often smells strongest. Running the hot taps for a while usually clears it for a time. If it keeps coming back, the anode or treatment is the long-term fix.
Will a new water heater get rid of the smell?
Not necessarily. A new tank comes with a new anode, and if it is the same type the smell can return. Ask about the anode type, or treating the water, when you replace the heater.
If your water smells of sulphur, the short form is free to use and sends your request to one local plumber who covers Ballantrae, Kettleby or your part of York Region.