Why your water tastes different than it used to

Tap water is not a stable product, and a utility meeting every standard it is held to can still deliver water that tastes noticeably different in April than it did in January. Most of the reasons are ordinary. A couple of them are worth acting on, and telling them apart is mostly a matter of noticing where and when the change shows up.

The reservoir changes through the year

A surface water system draws from a lake or a river, and those are living bodies of water with seasonal cycles. In spring and fall, many reservoirs turn over as surface and deeper water change places with the temperature, and that movement brings compounds up from lower in the water column that were not previously being drawn into the intake.

Two of those compounds, geosmin and methylisoborneol, are produced by algae and certain bacteria and are detectable by the human nose and tongue at extraordinarily low concentrations, far below any level that is regulated. They taste earthy or musty, sometimes described as dirt or as beetroot. Birmingham had a pronounced episode of this in May 2024, which we wrote about separately, and smaller versions of the same thing happen in a lot of systems most years without making the news.

Utilities treat for it, usually with activated carbon, and the treatment is about how much gets through rather than whether any does. None of this indicates the water is unsafe, and it is not reported as a violation, because taste and odor compounds of this kind are not regulated contaminants.

Chlorine residual is not the same everywhere

Utilities are required to carry a disinfectant residual all the way through the distribution system, which means the concentration leaving the plant has to be high enough that there is still some left at the furthest house on the network. If you live close to a plant, you are getting water that has had less time and distance to use its residual up, and it will generally taste more of chlorine than the same water does several miles away.

That residual also gets adjusted through the year, because warmer water consumes it faster. Summer frequently means more chlorine entering the system, which means more of it reaching you.

Shelby County Water Services, to give a concrete published example, reports a free chlorine residual range of 0.52 to 2.2 mg/L. That is a four-fold spread inside a single system and every value in it is compliant. A customer at the top of that range and one at the bottom are not drinking the same tasting water.

The least interesting explanation is often the right one

Cold water tastes better. Chlorine and most off-flavors are far more noticeable as the temperature rises, and water sitting in a pipe that runs through a hot crawlspace in August arrives warmer than the same water did in February.

If the complaint is seasonal and the water tastes fine after it has been in the refrigerator for an hour, the explanation is temperature rather than content. Running the cold tap for fifteen or twenty seconds before filling a glass clears the water that has been standing in the line and is worth trying before anything else.

When it is your house rather than the system

A few patterns point inward rather than outward.

If the taste is confined to one tap and the others are fine, the issue is in that fixture or the line feeding it, not in the water arriving at the house. If it appears only on hot water, the water heater is the obvious suspect, and a metallic or sulfurous taste on the hot side specifically is a known pattern involving the sacrificial anode rod. If it showed up after the house was empty for a week or more, stagnant water in the lines is the likely cause and flushing the system through for several minutes usually resolves it.

If a taste change arrives together with discoloration, or follows nearby construction, hydrant flushing or a main break, that one is worth calling the utility about rather than working out on your own. They will generally tell you what happened and whether anything is ongoing.

What actually changes the taste

For chlorine and for the seasonal earthy compounds, activated carbon is the mechanism that works, because both are organic compounds that carbon adsorbs well. That can be a pitcher, a faucet cartridge, an under-sink filter or a whole-home carbon unit, and the difference between them is scale and convenience rather than whether the chemistry works.

Softening does not address taste. It removes calcium and magnesium, and neither of those is what you are tasting when the water goes musty or chlorinous. This gets conflated often enough to be worth stating directly, because a softener bought to fix a taste complaint will not fix it.

If what you want is the taste handled at one tap rather than throughout the house, that is the ordinary case for a drinking water system at the kitchen sink, and it is the reason we publish that price rather than requiring a visit to quote it.