What does it cost to fix a water heater that smells like rotten eggs?

Q: What does it cost to fix a water heater that smells like rotten eggs?

If your water heater smells bad, Fixr's water heater repair guide (August 29, 2025) puts the fix at $200 to $600, and names the cause: hydrogen sulfide, which produces a rotten egg smell around the tank and is usually caused by bacteria or corrosion in the system. The same guide says the tank may need flushing and a new anode rod, which it prices at $125 to $300. Before any of that, settle one question. This Old House's safety guide lists a rotten egg smell as a possible sign of a gas leak, and there the instruction is to evacuate and call the gas company, not to book a plumber.

Answer this before you price anything

Two different things smell of rotten eggs around a water heater, and they are not comparable.

Where you smell it	What it is	What to do
In the hot water, at the tap	Hydrogen sulfide in the tank	A repair, $200 to $600 (Fixr)
In the air around a gas unit, with no tap running	Possible gas leak	Evacuate, call the gas company (This Old House)

This Old House's safety guide lists a rotten egg smell among the warning signs that could indicate a gas leak, and its instruction for that case is unambiguous: if you smell gas, immediately evacuate the house and call your gas company or emergency services.

Our test, marked as ours: run a hot tap in another room and smell the water itself. A smell that arrives with the hot water and fades when you shut it off is the tank. A smell that hangs in the air near the unit whether or not water is running is the case where you leave the building first. Neither source frames the distinction this way; both describe one half of it.

The repair price

Fixr's repair guide, for the tank case: if your water heater smells bad you may need to spend between $200 and $600 to get it fixed. Fixr's explanation: the bad smell is likely caused by hydrogen sulfide, which produces a rotten egg smell around the tank, it is usually caused by bacteria or corrosion in the system, and the tank might need to be flushed with a new anode rod as well.

That sentence contains the whole job, and Fixr prices its pieces separately:

Element of the fix	Cost (Fixr)
Flush and clean service by a professional	$100 to $250
Anode rod replacement	$125 to $300
Bad smell, as a single repair line	$200 to $600
Rust, if corrosion has gone further	$200 to $2,000

Note that the two components add up to roughly the repair line. A smell job that costs $600 is usually a flush plus a rod, not a single expensive part.

Why the anode rod is in the answer

The anode rod is a sacrificial metal rod that corrodes instead of the tank. That is what makes it the suspect in a smell complaint: the same chemistry that protects the steel produces hydrogen sulfide when it meets sulfate-reducing bacteria in the water.

Fixr's own framing ties the two together, listing the anode rod among the gas-unit components where issues arise and putting a new rod into the smell fix. The anode rod page covers the part on its own terms.

Our reading, marked as ours: if the smell returns within months of a flush, the rod is the variable to change, not the flush. Replacing the rod with a different alloy is the standard trade answer to a recurring sulfur smell. Fixr names the rod as part of the fix but does not distinguish between rod types, and we are not citing a price for an alloy swap because neither source publishes one.

The cheaper thing to try first

This Old House's maintenance guide gives the low-cost version: a sulfur smell might mean there is bacteria in the tank, which can often be resolved by flushing with a chlorine solution.

That is the $100 to $250 end of the range rather than the $600 end, and it is the sensible first move on a tank that has never been flushed. The maintenance page covers what a flush involves, and the noise page covers the other symptom that comes from the same neglected tank.

One caution from This Old House's own flushing guidance: on tanks with heavy buildup a full flush may loosen sediment and create new issues rather than improving performance, and in those cases it is better to stop and have the system evaluated.

When the smell is the tank ending

Fixr prices rust at $200 to $2,000 and a tank replacement at $600 to $2,000. A smell accompanied by discoloured water is no longer a bacteria problem.

Our conclusion, marked as ours: rotten egg water on a tank in good condition is a $200 to $600 nuisance. The same smell with rusty water on a tank past its expected life is a replacement conversation, and the repair or replace page is the one to read. Fixr publishes the four numbers; the line between them is ours.

Sources

Price figures are national US ranges from the sources above as of the date shown. Your local price depends on labor rates, permits and site conditions. Read how we get our numbers.