How does water hardness affect it? Mine is on the harder end, I've been wondering if that is giving me trouble.
Hard water will boil at a higher temperature, but it's only a degree or two.
Plus, pasta start cooking at 80 ºC. No need to keep the water boiling like crazy :)
Boiling like crazy or not, it's still just 100C if it's boiling at all isn't it?
I guess at a really low boil there could be cooler parts of the water.
Very soft. Elevation is nearly sea-level.
Well, objectively very soft water cooks things a tiny bit slower than harder water, but being close to sea level should cook things a little faster. It probably is down to either taste or the labeling on your pasta.