We have just installed our first above ground pool. It is an 18' round pool with metal poles that hold up the liner (Intex brand). We have checked the water level and found that the difference in water level height is approx. 3-1/2 inches from one side of the pool to the other. Is this a huge safety problem? If not, the uneven water level does not bother us, however if it may cause the pool to collapse, I want to fix it. Is it really dangerous, or will it be OK until we can find a more level spot next year?

You need to be as close to perfectly level as possible. With it not level, your pool is getting "pulled" toward the high end.

Yes, it could collapse. How soon from now, I cannot tell you... but if it were me I would not wait until next year to correct it.

To be sure, I'd call a local pool supply/maintenance company and tell them what model pool you have and describe the 3.5" difference and get their opinion too.

Hi,
I just finished tearing down a 15 x 30 by 4 ft deep above ground pool; after having it up for the last 24 yrs! No fun!
My wife and I installed it ourselves, and it's really been a lot of fun through the years, until now; we don't use it anymore with the children gone from home.
But, to your question, our pool had many, many pages of installation instructions. The MOST important one was:
The ground MUST be not more than 1/4 inch off level, all the way across, all directions. I actually borrowed a "transit" and a level rod from an engineer friend. I leveled the "level transit", then my daughter (10 yrs old then), held the level rod all around the pool area, taking readings, to be sure all points were within 1/4 inch of each other. Took a lot of time, digging out a little more, and adding some more sand here and there.
I would think that over 1 inch difference would be OK, but not as much as you say. I would "tear it back down", and re-level your ground area.
Since we live in the Appalachain Mountains, I hauled in sand, putting it about 3 inches deep all around the bottom, then tamped it down, before putting the pool cover over it... keeps small rocks from tearing a hole in the pool liner later on. Best of luck.

Thanks, (both of you) for your help. I will tear it down and start again.

Yes perfect, I had one that was not that much off that sent a flood of water into my neighbors yard one night when the wind hit it also.

Can you just add block to raise the side that the water is high on?

Since it is rare anyone will can PERFECTLY level the ground for these pools I do not recommend them unless you are a professional construction foreman