If you want to eliminate mercury and other toxins from the water you drink, then you can have a water filter plumbed in, but most people rely on using a water filter jug.
There are several brands of jug on the market, but the Rolls-Royce of them all seems to be the “ZeroWater”.
According to their website, it removes much greater percentages of chemicals in the water than other brands like Brita. The downside is that the filter cartridges are huge, and fairly expensive (£12 each)($15).
It’s reassuring that it removes metals like lead, mercury, and chromium, as well as pesticides and other pollutants like chlorine, fluoride, micro-plastic particles, and a long list of other nasties, although it’s not clear to what extent the filter removes hormones and antibiotics, which are now becoming an issue in some areas.
The ZeroWater filter jug comes with a gadget to test the solid content of your tap water, typically in the range 100 to 300. If you test the filtered water, the reading is zero, and in fact the way to tell if you need a new filter is when the reading starts to creep up from zero.
Link to my post on “Toxins in tap water“