Water can kill ants, but plain water alone is surprisingly ineffective. Ants have evolved multiple defenses against drowning, and most species can survive underwater for hours or even days. Adding soap or using boiling water dramatically improves your chances, though even the best water-based methods have real limitations.
Why Ants Don’t Drown Easily
Ants don’t breathe through their mouths like mammals do. They take in oxygen through tiny openings along their bodies called spiracles, which connect to a network of internal tubes. When submerged, ants can close these spiracles to seal out water, essentially holding their breath. While sealed up, they recycle the oxygen already inside their bodies, allowing them to survive without fresh air for extended periods.
On top of that, an ant’s exoskeleton is coated in a thin waxy layer that actively repels water. This coating reduces how much moisture can penetrate the body and helps trap small air pockets against the ant’s surface. The combination of closeable spiracles and a water-resistant shell means that simply dunking an ant in a glass of water won’t produce quick results. Some species can survive submerged for up to 24 hours, and certain ant types have been observed lasting even longer.
Fire Ants Can Float for Weeks
Fire ants take water resistance to an extreme. When floodwaters rise, entire colonies link their bodies together to form living rafts that float on the surface. Research from the Georgia Tech Ant Lab found that the tightly woven structure of these rafts is essentially waterproof, giving the colony enough buoyancy to stay afloat and keeping most of the ants dry. A layer of worker ants forms the base while the rest of the colony, including the queen and brood, rides on top.
These rafts can hold together for weeks until floodwaters recede or the colony finds dry ground to reestablish. So if you’re dealing with fire ants specifically, pouring water into a nest or hoping rain will solve the problem is unlikely to work. The colony will simply relocate.
Soapy Water Works Much Better
Adding dish soap to water changes the equation significantly. Soap breaks the surface tension of water, which is the invisible “film” that lets small insects walk on water and helps keep liquid from entering their spiracles. Without that barrier, soapy water penetrates the breathing openings directly, reducing the ant’s oxygen supply. According to the University of Georgia Cooperative Extension, part of soap’s effectiveness is literally drowning exposed insects by flooding their respiratory system.
A simple mixture of water and a few drops of liquid dish soap in a spray bottle can kill ants on contact. You can also fill a bucket with soapy water and pour it into a nest entrance. This method works best against ants you can see and reach directly. It won’t eliminate a deep colony with tunnels that extend several feet underground, but it’s a practical way to kill foraging ants or treat shallow nests.
Boiling Water: 60% Success Rate
Pouring boiling or near-boiling water directly onto an ant mound is one of the most common home remedies, and it does work, just not as reliably as people assume. Data from both the University of Tennessee and Texas A&M put the success rate at about 60% of treated mounds. That means four out of ten times, the colony survives.
You need roughly 3 gallons of very hot water per mound, and timing matters. The method works best when ants are gathered near the surface, such as on a cool, sunny morning during warmer months. If the queen is deep underground and the water cools before reaching her, the surviving ants will simply relocate and rebuild nearby. You’ll see the original mound go quiet and think the problem is solved, only to find a new mound a few feet away within days.
There’s also collateral damage to consider. Boiling water kills grass and any plants it touches. If the mound is in a garden bed or near landscaping you care about, you’ll scorch the surrounding vegetation along with the ants. Repeated applications to the same area can harm beneficial organisms in the soil as well.
Why Water Alone Rarely Solves the Problem
The core issue with any water-based method is that ant colonies are designed to survive disruption. A mature colony can have thousands of workers, multiple chambers, and tunnels that reach deep into the ground. Water, whether plain, soapy, or boiling, treats the surface. Unless it reaches the queen, the colony regenerates.
Most “successful” water treatments actually just force the colony to move. The ants aren’t dead; they’ve relocated to a spot a few feet or a few yards away. This is why university extension programs consistently note that home remedies “sometimes appear to work” but rarely eliminate colonies outright.
If you want to use water as part of your approach, soapy water is the most effective option for killing ants you can see. Boiling water gives you a reasonable shot at destroying a mound if you time it well and use enough volume. Plain water, without soap or heat, is the least effective option against an insect that evolved to survive floods.