Why Does My City Tap Water Smell Musty or Earthy Right Now?

If your tap water has started smelling or tasting a little “off” this week: earthy, musty, almost like a damp basement, you’re not imagining it. Reservoirs that supply city water are heading into peak algae season, and this is one of the most predictable seasonal complaints utilities get, every year around this time.

What’s happening with my water right now?

Late July into August is when reservoir algae blooms typically peak, releasing compounds called geosmin and MIB that the human nose can detect at just a few parts per trillion. Enough that even a modest bloom produces a noticeable smell. Your city’s treatment plant is very likely already aware and dealing with it; conventional treatment wasn’t designed to fully strip these compounds out, which is why the smell can linger for days or weeks once a bloom starts.

We covered the full mechanics of this, why it happens, why it’s worse in summer specifically, and how it differs from other causes of bad-smelling tap water in two earlier posts: Why Does Water Smell Worse in Summer? and Why Does My City Water Smell Bad? If you haven’t run into this before, those are the best starting points for the “why.”

Is this water dangerous to drink?

No. Geosmin and MIB are aesthetic issues, not health risks, they don’t indicate contamination or a treatment failure at your utility. Curious what else your city actually tests for and reports on? Is Your City Testing for This? walks through how to read your annual water quality report.

What can I do about this smelly water at home?

Since geosmin and MIB are notoriously resistant to standard treatment, activated carbon is the standard home-level fix.  It adsorbs the compounds rather than trying to break them down chemically. If the smell only bothers you at the tap or in your coffee, a point-of-use carbon filter is the fastest fix. If it’s noticeable in the shower, ice, and laundry too, a whole-house carbon backwash system treats water at the point it enters your home. We go through sizing and how these systems work in our Carbon Backwash Filter for City Water Guide.

Will water smell go away on its own?

Usually most utilities see complaints taper off as water temperatures drop later in the season. But if you’re on a surface water system, expect this to be a recurring late-summer visitor rather than a one-time event, which is why a carbon-based fix tends to be worth the investment once: it keeps working every year the bloom comes back.

Related reading

• • Why Does Water Smell Worse in Summer? City & Well Water Causes Explained
  • Why Does My City Water Smell Bad?
  • Carbon Backwash Filter for City Water: What It Does, What It Doesn’t, and How to Size It
  • Is Your City Testing for This?

Sources

• • EPA – Harmful Algal Blooms in Water Bodies
  • EPA – Managing Cyanotoxins in Public Drinking Water Systems
  • Illinois EPA – Cyanobacteria Bloom Information for Water Operators