Scotland here. We don't boil water before use.
I have family down in North West England that do have to do this, though. They live in an area where there is a thin layer of soil and a lot of clay. The water isn't particularly hard but it also doesn't taste very nice if you don't boil it first.
How long is "a while"? I've had it open for around 30 minutes now and I'm not seeing what you're describing. Around the 15 minute mark I also tried clicking through various tabs, performing some actions, etc. and memory usage is still staying steady at 247MiB.