FC levels with new vinal liner

[Erack]

Hello all!

It's been a while since I have posted because of all the great advise from the Pool School and here on the forum I haven't needed to. All is fine and pool looks great. I just had a new liner installed. My old one ripped this past winter. It was 14-15 years old so I guess I got my moneys worth out of it. I know that FC should be at a level based on CYA. I have a non-swcg pool and my CYA is between 45 & 50. Based on the chart here I maintain a FC of 7. My CC is 0, PH is 7.5, TA is ~95, CH is 40.

Here is my question/concern. The liner I got is a Loop-lok luxury liner and on their website they state this about FC. "In most areas of the country, a circulation range of 1.0 – 1.5 PPM of chlorine will do the job of killing off bacteria in water. Above this range high concentrations of chlorine will attack the liner, bleach it and shorten its life." I know for a fact I need FC of 7 based on my CYA. Is my level of FC going to adversely affect my liner? I would hate to harm my liner but I also want to maintain proper levels of FC to keep my pool safe and look beautiful. My old liner certainly faded/bleached out and became brittle in the end prior to it ripping. I am notorious for overthinking things and always going to worse case scenarios, hopefully by posting this I can get some accurate information to put my mine at ease.

Thanks in advance!

 

[Richard320]

They're basing that on unstabilized water -- no CYA. 1-1.5 FC with no CYA is pretty much tap water.

If you're scientifically-minded, study this graph. You'll see that at 50 CYA, your 7 FC has actually a little less of the OCl ions -- that's the aggressive bleaching stuff.

 

[Erack]

Thanks Richard! That graph is certainly a help and you have set my mind at ease.

One more quick question in relation to CH. Should I bump mine up some? It is at 40ppm as I stated in my original post. I know it is said in the school that CH is not needed in a vinyl pool, just wondering since it is so low should a bring it up some.

 

[Richard320]

It won't damage the liner any to have CH so low, but you may find the water foams a lot, especially right by the returns. I didn't believe it until I captured a whole bunch of rainwater. I use my spa as the settling basin so it ended up about 90% rainwater and it sure did foam. Once it all got mixed with pool water, it stopped. 200 CH is plenty if you choose to raise it. poolmath tells me that it would take 27 lbs. If you find a 25 lb bucket, that's close enough. Through evaporation and refilling, it will climb slowly over the season.

 

[Erack]

Thanks so much!