I live near the Mississippi River, and presumably our water comes from there. When the river gets low the water tastes different, and I seem to be the only person who can tell.
Probably a higher concentration of mineral ions in it, due to decreased flow of them down the river.
Most people are rather de-sensitised to the taste of their local water, even if does change a bit.
But you don't have to travel far, usually to taste a difference from a different source.
You could do a really basic test to see if there is any noticable change in concentration.
When the concentration is high, the water is "Hard".
When the concentration is low, the water is "Soft".
If you put soap in soft water it more readily forms "suds" or bubbles, and will froth and such easier.
In Hard water it doesn't do so as much.
You could try a simple (although possibly inaccurate) test by comparing how easily soap forms bubbles in the water, when you think the water is normal and when you think it tastes differently.
And if it is temporary hardness, then boiling it should clear it up.
