That rotten egg smell is hydrogen sulfide gas, and you get rid of it by oxidizing it into solid sulfur and filtering the solid out. Before you buy anything, work out where the gas is coming from: the well itself, the water heater, or bacteria growing in the plumbing. The wrong diagnosis buys the wrong equipment, and a softener alone will not touch it.
First, find out where the smell starts
Run the cold tap only, at a fixture close to where the water enters the house, and smell it. Then run the hot tap at the same fixture. If only the hot water smells, the problem is almost certainly inside the water heater, where the sacrificial anode rod reacts with sulfate and sulfur reducing bacteria in the tank. If cold and hot both smell, the gas is arriving with the water and the fix belongs on the main line. If only one distant fixture smells, you have a stagnant branch or a fouled aerator, not a supply problem.
Water heater odor is a different repair
When the smell is confined to hot water, replacing a standard magnesium anode rod with an aluminum or zinc alloy rod usually stops it, because the reaction that generates the gas slows down dramatically. Flushing the tank and raising the thermostat temporarily to disinfect it helps in stubborn cases, though that has scald implications and should be reversed afterward. Do this before you spend money on whole house treatment, because a heater problem will keep producing odor no matter what you install upstream.
Oxidize it, then filter the solid out
For water that arrives smelly, every real treatment works the same way. Something oxidizes dissolved hydrogen sulfide gas into elemental sulfur particles, and a media bed catches those particles and backwashes them to drain. Air injection systems draw a pocket of air into the top of the tank and pass water through it, which suits light to moderate odor and needs no chemicals. Chemical injection, usually chlorine or peroxide dosed by a small pump into a contact tank, handles heavier odor and bacterial sulfide, and is followed by carbon to strip the residual. Catalytic carbon alone can hold down a faint smell but is easily exhausted.
Bacteria in the well need shocking, not filtering
Sulfur reducing bacteria live in the well casing and the drop pipe and regenerate the odor after every treatment. Shock chlorination, where a measured dose of chlorine is circulated through the well and the household plumbing and then flushed out, clears the colony. It is a maintenance task rather than a permanent cure, and if the smell returns within weeks you have a continuing source, such as surface water reaching the aquifer or a failed well cap. Test for coliform bacteria at the same time, since the two problems travel together. Our well water testing guide covers the sampling order.
Why a softener will not fix it
A water softener exchanges hardness minerals for sodium on a resin bed. Hydrogen sulfide is a dissolved gas and passes straight through, and worse, sulfide will foul and discolor the resin over time, shortening the life of a unit you paid for. If you have both hard water and a sulfur smell, the odor treatment belongs upstream of the softener so the softener sees clean, oxidized free water. Installing them the other way around is one of the most common and most expensive sequencing mistakes in well water treatment.
Questions people ask about how to get rid of sulfur smell in water
Is sulfur smelling water dangerous to drink?
Hydrogen sulfide is mainly an aesthetic problem at household levels, but the smell often signals bacteria or a compromised well, so test for coliform and nitrate before assuming the water is safe.
Will boiling the water remove the sulfur smell?
Boiling drives off some of the dissolved gas, so a kettle of water may smell better, but it does nothing for showers, laundry or the rest of the house and is not a treatment.
Why does the smell come back after I shock the well?
Shock chlorination kills the existing bacterial colony but does not remove the conditions that let it grow, so recurrence usually means a continuing entry point or a permanent need for injection treatment.
Can a carbon filter alone remove hydrogen sulfide?
Catalytic carbon can hold down a faint odor for a while, but it loads up quickly at higher concentrations and gives no warning before it stops working, so it is not a standalone answer.