What are the causes of discoloration, deterioration and “dry rot” above the water line on a pool liner?
In most cases, these three problems are different stages of the same phenomenon. The causes of these problems are many and varied, but have a universal theme. In most cases, the discoloration (usually brown), the deterioration (stiffening of the vinyl) and then the complete failure of the vinyl, commonly referred to as “dry rotting,” is due to the extraction of the plasticizers and stabilizers from the vinyl. (Plasticizer is the additive which gives the vinyl its flexibility; stabilizers give the vinyl its high temperature stability.) Under normal circumstances, the volatility of these additives is very low and the vinyl will maintain its physical characteristics for many years.
Experience has taught us that under certain circumstances the area above the water line can begin to deteriorate very quickly. There are three main contributors to this problem: chemical attack, high temperatures and UV rays. However, the UV resistant characteristics of pool vinyl are excellent and the UV rays themselves do not present a significant problem.
Clean your pool often by taking a soft cloth and rinse the contaminates from the vinyl using the pool water. Substances such as body oil, sun tan lotion, baby oil, etc., will collect at the water line. These substances, when exposed to the sun and the high temperate that can be found just above the water lines, will oftentimes turn brown and can be very difficult to remove from the vinyl.
* The information provided comes from a vinyl manufacturer.