impact of FC on vinyl liner


Well-known member
Nov 12, 2012
Ontario, Canada
i don't if this the right section to post this, however we are planning to replace our vinyl liner this year. According to pool school the optimum levels for our swg pool is 70-80 CYA and target FC of 5-6. I am wondering what impact, if any this will have on the fading of the liner vs the FC=3 that my pool store recommends. I have seen my chem needs drop drastically since I started using tfp methods, but am I sacrificing the aesthetics and longevity of the liner?? Can it damage any equipment?


LifeTime Supporter
Aug 19, 2014
Pacific NW
The gist of it is, CYA buffers that harshness in the chlorine.

With no CYA for example, yes that would be quite harsh, even FC of 3 would be harsh on
the liner. Also you would lose it all within an hour in full sun.

The CYA protects it from burning off and protects your liner, clothing, hair etc with
its buffering effect.

I think "The ABC's of pool chemistry" goes into this further.

Out of wack PH would do much more everything.


In The Industry
Apr 5, 2017
The winter sun will do more damage than chlorine ever will. I have an old piece of liner that I left in pure 12.5% chlorine for a year and you couldn't tell any difference. Stay away from any cleaner that scrubs to hard. That will remove the ink off a liner very fast. Your swg inherently drives ph up by the tiny bubbles. A higher ph is far better than a low caustic one. You can limit that rise by keeping your alk around 50-60. Low ph will cause a liner to get very brittle very fast. One of the many reasons to stay away from net acidic pucks. Properly cared for your liner now a days will last 12-15 years. Years ago liners were made differently and it wasn't unheard of to see liners lasting 25 years. New EPA requirements won't allow manufacturers to make them that way anymore.


Well-known member
Nov 12, 2012
Ontario, Canada
Ours is original - almost 20 years old. It had its first hole last year and the tech recommended that we consider changing it. He said that sometimes they will just split open which could cause damage.