How do I find out...

[Van down by the river]

Please somebody with construction experience stop the madness.

I'm no engineer but I do have some common sense to administer.
The tank will weigh somewere between 1275 and 1500Lbs.

Now imagine you have a small party at your place. You got 6 buddies over to watch the Hockey game. They average 250Lbs each that's 1500 pounds. Now are you going to send some of your buddies home because you are worried your floor is going to collapse? Maybe you'll tell them to take turns watching in the living room so there's only 3 at a time? Of course not!

Your 150 is fine. If your floor can't handle it, you should probably move anyways. The waterbeds bylaws have to do with flooding not weight. Certainly placement close to a support wall would be much less stressful on the floor. There may be less flexing if it was a wood floor as well. As for cement, no problem at all.

Water damage insurance however is a good idea. Unfortunately if you have a flood it's your downstairs neighbors that will suffer the most.