blue, however, are susceptible to loss of color if they are exposed to high trichlor concentrations for a period as short as 6 hours. The reasons are a high available chlorine content of 90 percent, low solubility of the granules or puck, and the extremely low pH produced at the contact site.

Dichlor, calcium hypochlorite, and sodium hypochlorite (liquid chlorine) do not have as immediate or severe effect as long as they are not mixed with other chemicals during or shortly after they are added to the pool.

Solutions of these types of chlorine can be applied directly to the liner for a few hours to bleach out stains without adversely affecting the liner.

Take care to monitor the concentration of chlorine used for superchlorination or shocking, or else gradual bleaching of most blue liners will occur.

Pool Tar

Sticky substances known as “pool tar” can adhere and coat vinyl pool liners.

This is sometimes caused by the interaction of the quaternary ammonium compounds used in algicides with decaying leaves, grass, and insects.

A sticky material can also result from the interaction of chlorine with algicides. On pools using automatic chlorinators, the interaction of quatbased algicides with chlorine can result in a gummy material that is fed into the pool, gradually adhering to the liner.

Also, a beige, waxy substance can result through the oxidation of certain tanning lotions and cosmetics by high chlorine levels.

Sometimes, a light coating of vinyl plasticizer material, which turns darker when contaminated with dirt, can rise to the surface of newly installed liners during their first winterization. This is generally attributed to lack of circulation.

When the pool is re-opened for the season, allowed to warm up to about 70 degrees, chlorinated and circulated for about two weeks, it usually disappears.

Wrinkling and Stretching

Even in a properly sized vinyl liner, wrinkles can develop as the liner absorbs water, stretching it. The cause of excessive water absorption is usually attributed to high levels of chlorine. It is essential to control water chemistry to maintain the integrity of pool liners, because if sanitizers are allowed to remain high, as much as five times the normal amount of water can be absorbed.

Manufacturers have conducted immersion testing using chlorinated and brominated water in the 20-50 ppm range that has shown that liners continue to gain weight indefinitely, causing the liner to increase in size by as much as 3 percent.

Chlorine levels should not be allowed to remain higher than 3 ppm for an extended period of time to avoid stretching and wrinkling. Wrinkling caused by overusing chlorine or bromine to treat cloudy water introduced by bathers can be avoided by using a clarifier to coagulate particulates so they can be removed by filtration.

It is also important to control pH levels to prevent wrinkling.

A low pH of 7, for example, can cause a vinyl liner to discolor, wrinkle, stretch, lose strength, and increase in weight.

Meanwhile, a high pH of above 7.6 causes vinyl to wrinkle, shrink, lose weight, and expand.