Samiam, welcome to TFP!!
Mickey4paws- does the wrinkle run ~ parallel to the transition? If it does, I'm thinking you had water trucked in to fill the pool or , at least, set the liner (though a fire hydrant could do the same thing) - I won't WAG unless you tell me my suppositions are right
A quick primer on Ig liner pools and their bottoms
. Bases pros and cons:
Vermiculite
Pros:
Water passes through easily
Light and easily applied (usually*)
Not abrasive to the liner
Stable because of the cement in it
Cons:
Water passes through it easily (this lets ground water push the liner around - causing wrinkles
)
Dent's fairly easily when struck by heavy object
Mixed on site, inconsistent mixes often result in the 'Moon crater' effect
Critters and roots can easily burrow through it
Regular flowing of water through it will degrade the durability
Sand
Pros:
Cheap
Easy to apply
Non abrasive to liner
Water passes through it easily
Cons:
Tends not to stay where you put it :grrrr:
Sharp rocks if not properly screened
Dents VERY easily
Critters and roots can VERY easily burrow through it
Any steady stream of water will cause a chasm to form
Sand and cement (or concrete
)
Pros:
Durable (hard as a rock = very stable)
Water doesn't pass through easily
Premixed, so no inconsistent mixes
Critter and root resistant
Can use a 'screed' board to level, thereby reducing the 'Moon effect'
Cons:
Very abrasive to liners
Water doesn't easily pass through
Any ridge or a rock caught betwixt liner and bottom will damage the liner
Enough hydrostatic pressure will 'pop' up the floor
Expensive
With any of these you are at the mercy of how skilled the person applying it is!
BTW, 20 years is easily attainable for a liner pool - chemical abuse MUST be avoided
Samiam, the best way to test is with the drop based kit - Dave's tftestkit (in my sig) is as good as they come, but Taylor's 2006 - K is a decent approximation (Leslie's has their own rebranded version of it, but it's usually only available on line) :-D What you want is the "FAS/ DPD" chlorine test - that's what makes these kits preferable
Hope y'all enjoyed the read