Why your water smells like rotten eggs
Sooner Home Services
If only the hot water smells, it is the anode rod in your water heater reacting with sulfate bacteria — common, harmless and fixable. If both hot and cold smell, it is coming in on the supply. And often it is not the water at all, but the drain.
This page is about a smell in the water. If you smell rotten eggs in the air rather than from a tap, leave the building and call your gas utility or 911 from outside. Natural gas is deliberately given a sulfur smell so leaks get noticed.
Find your cause
Start here. Fill a glass of the smelly water, carry it to another room, and smell it there.
Drain bacteria smell exactly like sulfur water and are far more common. Thirty seconds separates them, and it saves people a service call constantly.
The glass still smells away from the sink
It is the water. Now run the hot tap for thirty seconds, then the cold, and smell each. This is the question that decides everything else — your water heater only touches the hot side, so if the cold is clean the heater is your answer.
Hot water only
The anode rod in your water heater. Every tank contains a sacrificial rod, usually magnesium, that corrodes so the tank does not. Where the water carries sulfate, bacteria feed on the hydrogen the rod releases and produce hydrogen sulfide. That is the smell, and it is why only the hot side is affected.
Three fixes, in order of permanence. Flushing and chlorinating the tank clears it for a few weeks. Swapping the magnesium rod for aluminium-zinc usually solves it for good. Removing the rod entirely stops the smell, voids the warranty and shortens the tank’s life — some will suggest it, and it is a poor trade.
Ask whether they will replace the anode rather than the heater. A tank that only smells is not a tank that has failed. What is fixable on a water heater.
Both hot and cold
The heater is ruled out. It is arriving on the supply, and where your water comes from decides the fix.
A private well
Groundwater in parts of Oklahoma carries naturally occurring sulfur, and sulfate-reducing bacteria live in many wells. Neither is unusual. Treating before testing means guessing at the dose, and the equipment is not cheap.
Test for hydrogen sulfide, iron and bacteria first. Low concentrations respond to activated carbon; higher ones need oxidation and filtration; a bacterial problem needs the well shock-chlorinated before anything else. A softener will not touch this, though it is frequently sold for it.
A city or rural water system
A sulfur smell on both sides of treated municipal water is unusual and worth reporting. It can mean stagnation in a low-flow section of main, something at the treatment stage, or a break in the line near you. Your utility is obliged to look.
Call before you spend anything on filtration. Ask whether there are other reports on your street, and whether your system has an open violation. Across Oklahoma, 317 of 847 active community water systems currently carry a violation or enforcement priority, so it is a reasonable question rather than an accusation.
If they find nothing, the next suspect is your own service line — a plumber rather than a filter salesman.
Cold water only
The heater never touches the cold line, so it is ruled out. That leaves the supply, a filter or softener that has gone anaerobic, or a branch of pipe where water sits still for long periods.
Check any point-of-use filter first — a cartridge past its life is common and cheap to fix. If the smell is worst at a tap you rarely use, stagnation in that branch is likely; run it hard for five minutes. If it is everywhere on the cold side with no filter involved, treat it as a supply problem.
No smell once I leave the sink
It is the drain, not the water. Bacteria build a film inside the P-trap and the overflow opening, and the smell lifts when running water disturbs it. This is the most common cause of a sulfur smell at a sink, and it has nothing to do with your supply or your heater.
Pour a kettle of boiling water down the drain, then half a cup of baking soda followed by white vinegar. Leave twenty minutes, flush with hot water. Clean the overflow opening too — that is the part people miss, and it is usually where the film is worst.
If the bathroom is rarely used, the trap may simply have dried out and let sewer gas up. Run the tap for a minute to refill it. No plumber needed for either of these.
Four things people get wrong
Buying a softener for it. Softeners exchange calcium and magnesium for sodium. They do nothing whatsoever about hydrogen sulfide. This is the most expensive wrong answer available and it gets sold constantly.
Replacing the water heater. A tank that smells is almost never a tank that has failed. The anode is a serviceable part costing a fraction of a replacement. If you are quoted a new heater for a smell alone, ask what is actually wrong with the tank.
Pulling the anode rod out. It works, and it is a bad idea. The rod exists so the tank corrodes last. Remove it and you have traded a smell for a shorter tank life and a void warranty.
Assuming it is dangerous. Hydrogen sulfide in water is detectable by nose far below any concentration of concern. At the levels that make water smell, it is unpleasant rather than harmful. The reason to fix it is that it is horrible to live with.
Related
Water heater repair for what else goes wrong with a tank, sewer smell in the house if the smell is in the air near a drain rather than in the water, and no hot water if the heater has stopped working altogether.
Water system compliance figures from EPA ECHO. Written by Jaylan Jones. Sooner Home Services earns a referral fee when a call connects to a contractor. See our business-model disclosure.