You can look for tiny holes in the liner if the pool is full of water. Follow these steps:
1. For holes on the side of the liner, look for a small stream of water seeping from the hole. These often are visible. Fix this hole with a patch. A dry patch can be used if the hole is higher than the water level. Otherwise, a wet patch is needed.
2. If the hole can't be located, fill a bucket with soapy water and rub it on the pool walls completely with a wet cloth. The hole will produce bubbles from the soapy water where the leak is coming out. Fix this hole with a patch. A dry patch can be used if the hole is higher than the water level. Otherwise, a wet patch is needed.
3. For holes on the floor of the liner, turn off the pump. Drain the pool until there is approximately 6-12 inches remaining. Drop some food coloring near where you believe the hole is. The direction the food coloring flows will show you where the hole is in the liner. The flow will be going toward the hole and out of the liner. You can now patch the hole to fix the issue.
You can use patches (either ones that came with your pool or ones you purchase from another retailer) to fix the hole. The use of patches purchased from other retailers will not void your warranty.