SonicAlbert
Super-Sonic "Herb" Albert
A440 is standard. If you want to jam with other musicians you definitely want to bring it up to 440. Like Lt. Bob said, if you have no plans to have other musicians over, then a lower tuning would be okay if you can stand it.
It will take several tunings to get the piano up to 440 and be stable. There are some very old pianos that won't hold a tuning, but that means they have technical problems.
As far as snapping strings, you can do that if you over tighten. But the strings are designed for the tension required to hold their respective pitch. So that intended pitch and under shouldn't cause them to snap. I could see an inexperienced tuner over tightening though, which could indeed snap them. Especially older and/or rusty strings. If they are in bad enough shape they might finally snap at lesser tension as well.
It will take several tunings to get the piano up to 440 and be stable. There are some very old pianos that won't hold a tuning, but that means they have technical problems.
As far as snapping strings, you can do that if you over tighten. But the strings are designed for the tension required to hold their respective pitch. So that intended pitch and under shouldn't cause them to snap. I could see an inexperienced tuner over tightening though, which could indeed snap them. Especially older and/or rusty strings. If they are in bad enough shape they might finally snap at lesser tension as well.