Last year I used one,,and it worked great, I used one underneath for my underlayment, then a good one on top., it worked fine, although was harder to disguise it with rocks, and the green algea kinda made it ugly, but worked until I could afford a regular liner. ( I assume you are referring to the blue liners of the wal-mat kinda pools,), one more thing when I took mine out this spring to put in a regular liner it was kinda brittle so it may not last more than a year or two,,but will get you by until you can save up,,,hope that helped,,

That's good information Ohio... I don't want to put all the time and energy into building the stream/waterfall I'm going to be doing soon and have to re-do it a couple of years later.
Anne

Well, I'm actually planning to use the liner from our above ground pool which we are taking down. The liner is only about 3 years old. I thought this would be a good use for it. It's the thickest you can buy at Watson's pool store.

I just built a huge 8,000 gallon pond and was thinking of doing the same. In the end i bit the bullet and bought the 45mil liner. The second I layed it down, there was my dog walking on it and I realized, good thing I did the right thing, her nails would be very difficult to cut through this one but probably not a pool liner, so keep that in mind!

My first pond, I used the liner from one of those pools with the blow up ring on top. The ring had a leak so I cut it to fit the hole I had dug, small I know, & used it ....it worked great. Looked funny with the blue polka dots on the bottom.

I made it bigger a few months later so just trashed the liner.