Why your water smells like a swimming pool — and what actually removes it

The pool smell is the most common complaint we hear, and it's almost always described the same way: it's worse in the shower, worse in winter, and it seems to come and go.

All three of those observations are correct, and all three have the same explanation.

What you're actually smelling

Central Alabama Water disinfects with free chlorine. Chlorine is added at the treatment plant and a residual is deliberately maintained all the way through the distribution system — that residual is what keeps the water safe across 4,100-odd miles of main between the plant and your tap. It's not an oversight. It's the entire point.

Free chlorine is volatile, which is why you smell it most in the shower: hot water and aerosolization drive it out of solution and into the air you're breathing. It's also why the intensity varies. Utilities adjust residual seasonally, and homes at different points in the distribution network see different levels — generally more near the plant, less at the far end of a run.

Free chlorine and chloramine are not the same problem

This is the part that has real money attached to it.

Many US utilities use chloramine instead — chlorine combined with ammonia. It's more stable, persists further through a distribution system, and produces fewer regulated disinfection byproducts. Good reasons to use it, and a lot of cities do.

But chloramine is considerably harder to remove. It's less reactive, so it needs longer contact time and a different media: catalytic carbon, which is surface-treated to accelerate the reaction. Catalytic carbon costs meaningfully more than standard activated carbon.

We specify Jacobi AquaSorb coconut-shell activated carbon for Birmingham systems, and we do it because it's the technically correct answer here — not because it's cheaper, though it is. We'll fit catalytic carbon if a customer wants it, and we offer it on the Whole Home Signature system as a genuine upgrade. But we won't present it as a necessity in a city that doesn't use chloramine.

If you get a quote in Birmingham that specifies catalytic carbon as a requirement, it's worth asking which disinfectant the quote assumes. The answer tells you how carefully the system was specified.

Why coconut shell, specifically

Activated carbon is made from several base materials — coal, wood, coconut shell — and they aren't interchangeable.

Coconut-shell carbon has a predominantly microporous structure, which suits small molecules like chlorine and many taste-and-odor compounds. It's also harder and more abrasion-resistant than coal-based carbon, so it holds up better through years of backwashing without breaking down and producing fines.

For municipal water where the target is chlorine, taste and odor, it's the right structure for the job.

Contact time is the thing that actually decides performance

Here's what most quotes don't tell you: activated carbon doesn't work instantly. It works by adsorption, which requires the water to stay in contact with the media long enough for the chemistry to happen.

The governing number is empty bed contact time — how long a given volume of water spends in the media bed. Two variables set it: how much media you have, and how fast the water is moving through it.

Which means media volume isn't a luxury spec. It's the performance spec.

This is why our systems step 2.5 → 3.0 → 4.0 cubic feet, and why we calculate a design peak flow for your house before quoting. A three-bathroom home with a soaking tub has genuinely different hydraulics from a two-bathroom home, and the same filter will not serve both well.

What carbon won't do

Worth being direct about the limits, because they're where overselling happens.

What to ask before you buy

• Which disinfectant does my utility use? In Birmingham it's free chlorine. If the quote assumes chloramine, it was written for somewhere else.
• How much media, and what kind? Cubic feet and base material. "Premium filtration media" is not an answer.
• What design peak flow was this sized for? If nobody calculated one, nobody sized it.
• Is it backwashing, or cartridge-based? Backwashing systems regenerate themselves. Cartridges need replacing every few months and lose flow as they load.

Those four questions will tell you more about a quote than the brochure will.