I have an old vinyl liner in my in-ground pool. The liner is about 12 years old and is at the end of its life--there are wrinkles in the liner on the stairs (previous owner was floating chlorine tabs...) and there had been a tear in the liner at one of those wrinkles that I MacGyvered with some silicone caulk. In the last few weeks, I noticed that my pool is leaking even when the pump is off (it will drop ~1/4" overnight and I'm refilling more than I was in the middle of the summer, so I'm confident it's a leak). I used a die test around the patch I made to the stairs, skimmer basket, light, and return jets and didn't identify any leaks. I haven't cared to swim to the bottom of the pool to see if there is an issue with the main drain. I've looked around the pool and don't see any obvious tears or holes in the liner. Would you replace the liner and see if that does the trick (since I know I'm living on borrowed time anyway) or would you bring in a leak detection company first to confirm it's not the plumbing (~$500)?