That rotten egg smell is hydrogen sulfide gas, and it is almost never a plumbing emergency. In most West Michigan homes it is coming from one of three places: the water heater, the water supply itself, or a drain. The most common fix we do is an anode rod replacement, about $450 installed.
Why does my water smell like rotten eggs?
Hydrogen sulfide. It is a gas produced by bacteria that live without oxygen, and the human nose can pick it up at concentrations far below the level that would do you any harm. That is why the smell can be overwhelming while the water itself tests fine. Penn State Extension puts the smell threshold at a fraction of a part per million, which is why one homeowner is gagging over the bathroom sink while a lab report comes back unremarkable.
The gas gets into your water in three different ways, and they need three different fixes:
- Inside the water heater. Sulfate in the water reacts with the magnesium anode rod, the sacrificial metal rod that protects your tank from rusting. This is the number one cause we find in homes on city water.
- In the water supply. Well water in parts of Kent and Ottawa County carries sulfur naturally. Softeners and older filters can also grow the bacteria inside the tank if they have not been serviced.
- In the drain, not the water. Bacteria feeding on gunk in a drain, or sewer gas getting past a dry trap or a bad vent, smells exactly the same to your nose while your water is perfectly clean.
Almost every wrong repair on this problem comes from skipping the diagnosis. A homeowner smells sulfur, reads that sulfur means well water treatment, and buys a filter. Then the smell is still there, because the gas was being made inside a 40 gallon tank in the basement, or in the trap under the sink they were standing at. Ten minutes of checking beats a thousand dollars of equipment.
Is water that smells like rotten eggs safe to drink?
Usually yes. Hydrogen sulfide at the levels that make water smell bad is a nuisance, not a health hazard, and it is detectable by smell at roughly one thousandth of the concentration that matters medically. There is no federal drinking water limit for it, because taste and odor give you a warning long before it reaches a toxic level. What it can do is corrode metal, stain fixtures a brown or black color, tarnish silverware, and ruin the taste of coffee.
Two situations are worth taking more seriously. If the smell arrived with cloudy or discolored water, or after a flood, a main break, or work on the street, get the water tested before you drink it. Sulfur bacteria are harmless on their own, but the conditions that let them bloom can also let other things in. The EPA's private well guidance is the plain English version of what to test for and when.
And if the smell is more like raw gas or garlic than eggs, stop and treat it as a possible natural gas leak: leave the house and call your gas utility, not a plumber. Mercaptan, the odorant added to natural gas, is often described as rotten eggs too, and that confusion is the one dangerous version of this question. Gas smells strongest in air near the appliance. Hydrogen sulfide in water smells strongest at the tap, in the water itself, and follows the water rather than the room.
Hot water only? It is almost certainly your water heater
Run the cold tap for 30 seconds and smell it. Then run the hot. If only the hot side stinks, the problem is inside your tank and your water supply is fine.
The magnesium anode rod is doing its job a little too well. Magnesium is reactive on purpose: it gives up electrons so the steel tank does not. In water carrying sulfate, that same reaction feeds sulfate reducing bacteria, and the byproduct is hydrogen sulfide. Swapping the rod for aluminum or zinc slows the reaction. A powered anode removes it entirely, because it protects the tank with a small electrical current instead of a metal that dissolves.
A powered anode installed at the hot water outlet on an NSP job. No sacrificial magnesium means no reaction to feed the bacteria, and no rod to replace every few years.
On a June 2026 call on the northeast side, a homeowner had a sulfur smell only on the hot side plus brown staining in the kitchen sink. Same fix, and the staining went away with the smell.
$450 for the anode rod replacement is the typical invoice. Nothing about that job is exotic: we shut off and drain part of the tank, break the rod loose from the top of the heater, and set the new one. The reason it is a plumber's job rather than a Saturday project is clearance and torque. Most basements do not have four feet of headroom above the tank for a straight rod, which is why segmented and flexible rods exist, and a rod that has been in place a decade often needs an impact wrench to move without twisting the tank fitting.
If the tank is also full of sediment, a flush and inspection at $149 typical often gets done at the same visit. Sediment matters here for a specific reason: it insulates the bottom of the tank, creates a warm oxygen poor layer, and gives the bacteria a place to live even after you change the rod.
Inside the bottom of a tank we opened up in West Michigan. That crust is the habitat. Change the rod and leave this, and the smell can come back.
If the tank is past 12 years old, spending money on a rod is throwing good money at a bad tank. The manufacture date is on the data plate, usually encoded in the serial number, and it takes ten seconds to read.
Every tank carries its own age. Read the data plate before you spend $450 on a rod, because on a 13 year old heater that money belongs in the replacement instead.
Our post on how long a water heater lasts covers that call, and water heater service is what to book if you want us to make it.
One thing worth knowing: raising the tank temperature to 160 degrees will kill the bacteria, and plenty of forums recommend it. It also scalds. Water at 160 degrees can cause a serious burn in about half a second, which is why manufacturers label 120 degrees as the setting for normal use. If you have kids or older adults in the house, do not run a tank hot without a thermostatic mixing valve at the heater to temper what actually reaches the fixtures.
Cold water too? Then it is the water itself
If both sides smell, the gas is arriving in the water before it reaches your heater. On a private well that usually means naturally occurring sulfur, and the fix is treatment sized to the reading: an air injection or oxidizing filter for a real sulfur problem, activated carbon for a mild one, and chlorination followed by filtration when bacteria rather than geology is the source.
That is water treatment and water filtration work, and it needs a water test first so you are not buying equipment for the wrong problem. A useful test panel for this complaint covers hydrogen sulfide, sulfate, iron, manganese, pH, hardness and coliform bacteria. Michigan's EGLE drinking water program is the state reference for well owners, and county health departments in this area handle well water sampling.
On city water, a whole house smell more often traces back to equipment you already own. Municipal water arrives with a disinfectant residual, so the gas is rarely coming down the street. Some of our recent smell calls were the water softener itself: the resin tank had grown bacteria and was flavoring every fixture in the house.
A typical basement treatment stack. The resin tank in the middle is a dark, wet, low flow environment, which is exactly where sulfur bacteria settle in when a unit goes years without service.
A sanitizing cycle sometimes clears it. When the unit is old enough that the smell keeps coming back, replacement runs $775 to $2,600, most commonly around $1,200, depending on grain capacity and whether iron removal is bundled in.
There is a fast test before you spend anything. Put the softener on bypass, run the cold water for a few minutes, and smell it again. If the smell disappears, your water was fine and your equipment was the source.
The bypass on most softeners is two handles. Turning them takes a minute and tells you whether to sanitize the unit or go looking somewhere else.
Also check whether the smell shows up on water that bypasses your treatment gear. One customer in June 2026 only smelled it on the outside hose and the sprinkler line, which is exactly what you would expect from an outdoor spigot plumbed in ahead of the softener.
Only one faucet, or only when the drain runs? Then it is not your water
This is the one most homeowners get wrong, and it is the cheapest to fix.
One fixture only. In July 2026 we took a call for a strong rotten egg smell at a single bathroom sink, with the shower and every other fixture clean. Water that smells at one faucet and nowhere else is not a water supply problem. It is biofilm in that drain or that faucet aerator. Pull the aerator, look at the screen, and clean the overflow hole in the basin while you are there. A guest bath that gets used twice a month is the classic offender.
Smell strongest when the water is barely trickling. Another July call described the odor showing up at a low drizzle and disappearing when the faucet was opened all the way. That pattern points at the drain and the vent, not the water. Slow flow lets air pull back up out of the drain past the trap. Full flow pushes it down.
Only in one room, only sometimes. A trap that dries out, usually a floor drain in a laundry room or a basement, lets sewer gas straight into the house. Pour a couple of quarts of water into it and see whether the smell goes away for a week. If it does, that trap is the problem and it needs to be kept wet or fitted with a trap primer.
Across the last twelve months of NSP smell and odor calls, the water itself was the cause on a small minority of them. The large majority were drains, sewer gas, dry traps and vents. That ratio is the single most useful thing in this article: if your nose says rotten eggs, the odds favor a drain.
So a drain cleaning visit fixes more of these calls than water treatment does, and it costs a lot less than equipment. Our post on sewer smells and basement backups covers that side of it, and it also explains how to tell whether you are dealing with one fixture or the whole main line.
Test it yourself in five minutes
Do this before you call anybody. It narrows the problem to one of three answers and it saves you money on the visit.
- Fill a glass at the kitchen cold tap, step outside, and smell it. No smell outside the room means you are smelling a drain, not your water.
- Run cold for 30 seconds, then hot. Hot only means the water heater.
- Check a second bathroom and an outside spigot. Everywhere means the supply. One fixture means that fixture.
- Put any softener or filter on bypass, run cold for a few minutes, and smell again. Smell gone means the equipment is the source.
- Note whether it is constant or only after the water has sat unused overnight. Sitting water that smells and then clears points at the heater or the softener tank.
- Write down when it started. New construction, a recent softener install, a well pump repair or street work are all real triggers.
| What you notice | Most likely cause | Typical fix and cost |
|---|---|---|
| Hot water only | Anode rod reaction in the water heater | Anode rod replacement, about $450 |
| Hot water only, plus sediment or rumbling | Tank needs service | Flush and inspection, $149 typical |
| Hot and cold, every fixture, city water | Softener or filter growing bacteria | Sanitize, or replace at $775 to $2,600 |
| Hot and cold, every fixture, private well | Naturally occurring sulfur | Water test, then treatment sized to the result |
| Smell stops when equipment is bypassed | The treatment equipment itself | Sanitize or replace that unit |
| One fixture only | Biofilm in that drain or aerator | Drain cleaning at that fixture |
| Worst when water trickles, or near a floor drain | Dry trap or venting issue | Drain and vent diagnosis |
What we actually do on the visit
The diagnosis is the job. A technician runs the hot and cold split at more than one fixture, checks the age and condition of the heater and pulls the anode if the pattern points there, puts your treatment equipment on bypass to rule it in or out, and runs the affected drains. On a well, that includes looking at the pressure tank and asking when the well was last shocked and tested.
Then you get told which of the three causes it is, and quoted in writing before anything gets done. Most of these calls end in a rod swap, a drain cleaning or a sanitizing cycle. A minority end in new equipment, and when they do, it is because the equipment was already at the end of its life.
Three things make this visit go faster, and they are worth doing before we arrive. Leave the affected fixture alone for a few hours so the smell is present when the technician gets there, because a bathroom that was just run for ten minutes often tests clean. Know roughly how old the water heater and the softener are, or at least clear a path to their data plates. And say up front whether you are on city water or a well, since that single fact changes the whole diagnostic order.
What we will not do is sell you treatment equipment off a smell alone. On a well, a real sulfur problem gets confirmed with a test before anything is sized, because air injection, carbon and chlorination are three different systems at three different prices and the wrong one leaves you with both the smell and the bill.
How to keep it from coming back
- Flush the water heater once a year, or twice if you are on a well with sediment. It takes the habitat away.
- Ask which rod is in your tank when a heater gets installed. If you have had sulfur smell before, aluminum, zinc or a powered anode is the better choice from day one.
- Service the softener on schedule and use clean salt. Cheap rock salt leaves more insoluble residue in the brine tank.
- Run water in unused bathrooms and pour water down unused floor drains once a month.
- On a well, test annually for bacteria and after any work on the well, the pump or the plumbing.
- Do not chase a smell with chlorine forever. Two rounds without a lasting fix means the cause has not been found yet.
Why does my hot water smell like rotten eggs but the cold water is fine?
The magnesium anode rod in your water heater reacts with sulfate in the water and produces hydrogen sulfide inside the tank. Replacing the rod with aluminum, zinc or a powered anode stops it. That job runs about $450 in our area, and it is worth doing only if the tank has years left in it.
Is it safe to shower in water that smells like rotten eggs?
Yes, at the levels that produce a noticeable smell. Hydrogen sulfide is detectable by nose far below any harmful concentration. If the water is also discolored or cloudy, or the smell showed up right after a main break or flooding, get it tested before drinking it.
Why does only one faucet in my house smell like rotten eggs?
Because the smell is coming from that fixture, not your water. Bacteria build up in the drain and in the faucet aerator, and the gas releases when water disturbs it. Clean the aerator and clear that drain. If the smell is gone, your water was never the problem.
Can a water softener cause a rotten egg smell?
Yes. Sulfur bacteria colonize the resin tank, especially in a unit that has gone a long time without service, and every fixture in the house then smells. Put the unit on bypass and run the cold water: if the smell disappears, that is your answer. Sanitizing sometimes clears it, and if the smell returns the unit is usually near the end of its life.
Does city water in Grand Rapids smell like sulfur?
City water arrives treated and should not smell. When a home on city water smells like sulfur, the source is nearly always inside the house: the water heater, a softener or filter, or a drain. Private wells in the surrounding townships are a different story, since sulfur occurs naturally in some aquifers here.
Will bleach or a shock treatment fix it permanently?
It buys time. Shocking a well, a softener or a heater kills the current colony but leaves the conditions that grew it. If the smell comes back within a few months, you need a rod change, a treatment system or a service replacement rather than another round of chlorine.
Should I turn the water heater up to kill the bacteria?
It works and it is a burn risk. Water at 160 degrees scalds in well under a second, so no tank should be left there without a thermostatic mixing valve tempering the water going to the fixtures. Changing the anode rod solves the same problem without putting your household at 160 degrees.
How much does it cost to find out what is causing it?
Less than guessing. A technician checks the hot and cold split, the heater, your treatment equipment and the affected drains in one visit. Our invoiced repairs on these calls have run from a drain cleaning at the low end to softener replacement at the high end, and we quote the repair in writing before starting.
Get a straight answer on your water
NSP Plumbing is a licensed Michigan plumbing contractor, license #8004990, based in Wyoming, Michigan. We work on water heaters, softeners, filtration and drains every day across Grand Rapids, Byron Center, Caledonia, Kentwood, Grandville, Jenison and Hudsonville.
If you want the whole system looked at rather than one symptom chased, a plumbing inspection covers the heater, the treatment equipment and the drains in one visit.
If you have already decided the water itself is the issue, reverse osmosis is worth reading before you buy anything. And if you ever need to shut the water off in a hurry, know where your main shutoff valve is first. You can also reach us here.
Smelly water? We will tell you which of the three causes it is.
A technician checks hot versus cold, your heater, your softener and the drains, then quotes the repair in writing before anything gets done. Most of these calls end in a rod swap, a drain cleaning or a sanitizing cycle, not new equipment.
