Why does my water taste or smell earthy, musty, or moldy?
An earthy or musty taste is usually caused by natural, harmless compounds from algae — or occasionally by bacteria growing in your drain or pipes.
The likely causes
Two compounds released by algae and bacteria in lakes and reservoirs, especially in warm months. Your nose can detect them at incredibly tiny, harmless amounts.
A musty smell that appears only at one sink is often bacteria in the drain, not the water. Smell a glass of the water away from the sink to tell them apart.
Is it dangerous?
Geosmin and MIB are not harmful — they are the same compounds that make beets and fresh soil smell earthy. This is an aesthetic problem, though a persistent musty smell paired with cloudiness is worth a closer look.
How to tell what it is
Pour a glass and step away from the sink. If the water itself smells fine, the odor is coming from your drain. If the water smells musty everywhere, it is coming from the source.
The fix
Activated-carbon filters — pitcher, faucet, or under-sink — are very effective at removing earthy and musty tastes. If the smell is the drain, clean it rather than filtering the water.
If the musty smell is only at one sink and the water smells clean in a glass elsewhere, no water filter will help — the problem is the drain.
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