Every summer, utilities across Canada field the same complaint: the water tastes earthy, musty, or of chlorine. Nothing has gone wrong. Warm weather changes water in several predictable ways at once.
Algae is the usual culprit
Warmer lake and reservoir water encourages algal growth. Even blooms that pose no health risk release two compounds — geosmin and MIB — that the human palate detects at extraordinarily low concentrations, in the parts per trillion.
Conventional treatment removes the algae but not always those compounds, which is why water can be perfectly safe and still taste of pond. If your water tastes earthy in July and fine in February, this is almost certainly why.
More chlorine, deliberately
Chlorine dissipates faster in warm water, and bacteria multiply faster too. Utilities respond by increasing the dose so a protective residual survives the whole distribution network.
The stronger chlorine taste in summer is the system working as designed, not failing. It is also the easiest of these problems to fix at your tap.
Water that has been sitting
Summer means holidays, and a house empty for two weeks leaves water standing in the pipes. Standing water picks up more from the plumbing and loses its chlorine residual. Run the cold tap for a minute or two after any absence before drinking or filling a kettle.
Warmer water simply tastes worse
The mundane explanation people overlook. Cold water suppresses flavour perception; the same water at room temperature tastes noticeably more of whatever it contains. Summer tap water arrives warmer because the pipes it travels through are warmer.
A jug in the fridge fixes a surprising proportion of summer taste complaints on its own, at no cost.
What actually helps
For chlorine taste, any activated carbon filter works — pitcher, faucet mount, under-sink or fridge cartridge. This is what carbon does best.
For earthy or musty taste, carbon also helps, though geosmin is stubborn and a higher-grade carbon block will outperform a basic pitcher cartridge.
Change your cartridge on schedule. Summer is when filters work hardest, so a cartridge that was fine in spring may be exhausted by August. If taste returns suddenly, suspect the filter before the utility.
Replacement intervals → · More on chlorine →
When it is not just seasonal
Taste changes worth reporting rather than filtering: a metallic taste that appears suddenly, anything resembling fuel or solvent, or water that is discoloured or cloudy for more than a few minutes after running. Those are utility calls, not filter problems.
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