A rotten egg smell appearing in well water raises three questions at once, and the equipment question is the least urgent of them. What people actually want to know first is whether the water is safe to use today, whether the smell means something has changed at the well, and what can be checked in the next hour without spending anything.
Is it safe to use
Hydrogen sulfide at the concentrations that produce a household smell is an aesthetic problem rather than an acute hazard, and it is detectable by nose far below any level of concern, which is why the smell is often much more alarming than the situation. That said, a smell that has appeared suddenly on a well that never had one is a change, and change is what should prompt a test rather than a purchase. Until you have one, the water remains usable for washing and the caution applies to drinking.
The two checks to do today
Smell the cold and hot taps separately at two fixtures well apart. Hot only means the water heater is producing the gas, where bacteria interact with the sacrificial anode rod, and the supply itself is fine, which is both the most common cause and the cheapest to fix. Then look in the toilet cistern: a dark slippery film returning within days of cleaning points at sulfur bacteria in the well, while clear water with a smell and no film points at dissolved sulfide, which is chemistry.
What a sudden change might mean
A smell that appears abruptly deserves more attention than one that has always been there. It can follow a change in the water table, heavy rain, work on the well or the pump, or a period of low use that let bacteria establish. It can also accompany surface water reaching the casing, which is a contamination question rather than an odour one. So a new smell belongs with a coliform test and a look at the wellhead, the cap and the ground slope around it.
Then, and only then, the equipment
The EPA notes that private wells are not federally regulated under the Safe Drinking Water Act, so the test is the owner's responsibility and it is what sizes any system: sulfide is detectable well below the levels that decide equipment, so the strength of the smell is a poor guide. Test sulfide alongside iron, manganese and pH, since the treatment interacts with all three, and only then choose between catalytic carbon, air injection, greensand or chemical feed. Our well filtration guide covers matching media to a measured level.
Questions people ask about rotten egg smell in well water
Is water with a rotten egg smell safe to drink?
At household levels it is an aesthetic problem rather than an acute hazard, though a sudden new smell should prompt a test.
What should I check first?
Whether the smell is on the hot side only, which points at the water heater rather than the supply and is the cheapest fix.
Does a sudden smell mean something changed?
It can: a change in the water table, heavy rain, work on the well, or surface water reaching the casing. Test for coliform too.
Can I size treatment by how strong the smell is?
No. Sulfide is detectable far below the levels that decide equipment size, so a laboratory test is what sizes a system.