Hi folks. Our pool construction was completed late in the season last year, so this is our first full season. We have had a couple algae episodes due inexperience and letting FC fall out of ideal range. We are concerned about damaging the vinyl liner by raising FC to shock level and beyond to mustard algae level if the need arises. Our liner warranty paperwork says maintain FC between 1 and 3, and I realize this probably does not account for CYA level. All that being said, does anyone know or have experience with what FC level would actually damage a vinyl liner?
What FC level would it take to visibly damage vinyl liner?
- Thread starter jmattdoss4
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Great question. The answer is variable with your CYA level. Anythink up to SLAM level should be safe and up to mustard algae level for short periods. The key to avoiding liner damage is to make sure that your chemistry is mixed in properly (pour in front of a jet, sweep the pool, pump on high etc.) Most chemistry related (as in application not out of balance) liner (and plaster) damage is due to chemistry sinking to the bottom and working on the liner instead of any organics in the pool. I have a very nice ring around the deep end of my pool (plaster damage) from the prior owners doing exactly this.
You would need to maintain the FC at/above mustard shock level (function of CYA) for an extended period of time to have fading occur.
Normal shock level should be fine ... and for mustard (rare) you only are at the higher level for 24 hours.
Normal shock level should be fine ... and for mustard (rare) you only are at the higher level for 24 hours.
Ok thanks. Unfortunately, we may be dealing with mustard algae, so that is why I'm asking. Our CYA is around 40-45, and we are nervous about running FC up to 24-26 on a brand new liner. We usually dilute a pint of bleach in a 3 gallon bucket of water, then pour that in front of the jet in the deep end. I will also pour some in front of the jets in the shallow end too, just not as much at one time. We also use this method for MA as well. Do we also need to sweep / stir? We have not been doing that.
When I'm manually pouring chemistry in I try to do a quick sweep of the bottom. I'm a bit OCD... If you have nice strong jets going it probably isn't necessary. Given that you are doing pre dilution ... it probably isn't necessary to sweep. given the volumes of bleach for an MA SLAM I would skip the pre dilution and add a sweep for the time being.
If you were at 26 ppm FC with 40 ppm CYA, then assuming a warmer pool temperature of 90ºF and even accounting for chlorine bound to CYA being 1/150th as strong as HOCl, then this is roughly equivalent to around 3 ppm FC with no CYA so at the upper limit of what the manufacturer recommends as a permanent level of chlorine, not short-term. At cooler water temps, there will be less active chlorine unbound to CYA.
@Chem geek: That's awesome! I think...can you interpret that for me? I think you said at FC26/CYA40 we're not even close to damage level? What would that number (to cause liner damage) be? (Although I don't ever plan to go there...just curious).
He said at 26/40 and if your water was hot, then you are at the same damaging level as a FC of 3ppm with 0ppm of CYA (which is what the manufacture seems to be indicating as a max). He did not say at what level you will start to actually see immediate damage.
These levels will still be more damaging than the normal levels that we recommend.
These levels will still be more damaging than the normal levels that we recommend.
