Start with taste and smell
If your tap water tastes clean and pleasant at room temperature, brew with it first. If it smells strongly of chlorine, tastes metallic, or leaves heavy scale in the kettle, filtration or different water may improve the cup.
TDS is not the full answer
Total dissolved solids, or TDS, reports how much material is dissolved in water. It does not tell you what those minerals are. Two waters can show the same TDS and brew very differently.
The two most useful ideas are:
- Hardness: mainly calcium and magnesium, which help extract flavor.
- Alkalinity: the water’s ability to buffer acidity. Too much can make coffee taste flat; too little can make acidity feel sharp.
That is why “use exactly 150 TDS” is not reliable advice.
Practical options
Filtered tap water
A carbon filter can reduce chlorine and unwanted odors. It does not necessarily soften very hard water, so kettle scale may remain.
Bottled water
Choose still water with a moderate mineral level and a clean taste. Avoid distilled water by itself and heavily mineralized water.
Remineralized water
Coffee-specific mineral packets can make brewing more repeatable, but they are optional. They are most useful when local water is unusually hard, soft, or inconsistent.
Protect your equipment
Hard water leaves scale in kettles and coffee makers. Descale according to the manufacturer’s instructions rather than waiting for flow or heating to fail. Never mix cleaning chemicals, and rinse the equipment thoroughly before brewing again.