Short answer: because water isn’t draining the way it should.
When artificial turf smells after rain, it’s almost never the turf fibers themselves. The smell comes from what happens when water lingers in the system instead of moving through it. Once moisture gets trapped, bacteria, mold, and mildew move in—and that’s what you’re smelling.
In almost every case, the problem starts below the surface.
A properly built turf system is designed to drain fast. Rain should pass through the fibers, down through the infill, through the backing, and into the base layers without hanging around. When that process slows down or stops, water pools. And pooled water turns into a breeding ground for bacteria.
The most common cause is poor drainage in the base. If the sub-base wasn’t graded correctly, compacted unevenly, or built with the wrong materials, water collects in low spots instead of flowing away. Even a slight dip can hold moisture long enough for odors to develop.
This gets worse when installers don’t account for native soil. Building a permeable base over heavy clay, for example, can create a bathtub effect. Rain goes in, but it doesn’t leave.
Over time, infill can become compacted—especially in high-traffic areas or pet zones. Once that happens, it stops draining efficiently and starts holding water like a sponge. Some infill materials, particularly heavier sands, make this problem worse.
Low-quality turf backing can also contribute. Cheaper products often have fewer drainage holes, and those perforations can clog with fine debris. When that happens, the backing stops shedding water and stays damp underneath the surface, allowing mold to grow where you can’t see it.
If you have dogs, rain can make the smell more noticeable. Old urine residue trapped in the fibers and infill gets reactivated by moisture. As it breaks down, it releases ammonia, which rises back up as the water evaporates. That said, pet odor usually becomes a serious issue only when drainage is already failing.
Vinegar, enzyme cleaners, and deodorizing treatments can help temporarily. They kill bacteria on the surface. But if water keeps pooling underneath, the smell will return after the next rain. Cleaning treats the symptom, not the cause.
A quick way to confirm this: pour water onto dry turf. If puddles or soggy spots remain for more than an hour, drainage isn’t doing its job.
Turf should not smell after rain.
When it does, it’s a sign that moisture is getting trapped somewhere in the system—often in the base, infill, or backing.
The odor isn’t the problem. It’s the warning.
Until water can move freely out of the turf system, the smell will keep coming back, no matter how often you clean it.
The fix starts underneath.
