Another shock question

[CarlD]

If you look at the DPD-FAS test, there are two ways to use it:
1) with 10ml of pool water. Then each drop of the re-agent represents .5 ppm
2) with 25ml of pool water. Then each drop of the re-agent represents .2ppm, allowing greater precision.

[kjsmom]

What is the highest SAFE, NO FADE chlorine level for shocking an inground vinyl liner pool? Last Spring, I was advised on the forum that I could safely go up to 10-12 ppm chlorine for shocking, and I did maintain that level until the water cleared -- about a week.

In August we had a big storm and had to put a patch on the liner -- I was totally shocked at how faded my 2 year old liner was!

We replaced the liner last Fall, and I would like to preserve the color. I called Pacific Pools and was told not to go over 3ppm chlorine, (1 1/2 - 2 ppm chlorine for maintenance); that's a big difference.

If it took a week to clear the water at 12 ppm chlorine, how long will it take at 3 ppm chlorine (the water was pretty nasty dark olive green).
Pat

[aylad]

What is the highest SAFE, NO FADE chlorine level for shocking an inground vinyl liner pool? Last Spring, I was advised on the forum that I could safely go up to 10-12 ppm chlorine for shocking, and I did maintain that level until the water cleared -- about a week.

In August we had a big storm and had to put a patch on the liner -- I was totally shocked at how faded my 2 year old liner was!

We replaced the liner last Fall, and I would like to preserve the color. I called Pacific Pools and was told not to go over 3ppm chlorine, (1 1/2 - 2 ppm chlorine for maintenance); that's a big difference.

If it took a week to clear the water at 12 ppm chlorine, how long will it take at 3 ppm chlorine (the water was pretty nasty dark olive green).
Pat

It depends on your CYA level--at higher CYA levels you have to maintain higher minimum chlorine levels to keep your pool clear. See the "Best Guess" chart (first thread in this forum) for a guide on how high your Cl levels need to be.

Janet

[CarlD]

Pat:
Liners fade. There's nothing you can do about that. UV rays will simply fade all liners, regardless of chlorine. Chlorine levels at 15ppm with no CYA will fade them faster, that's all.

I can see how my liner faded in two years from the drop-in steps. That spot is darker than the rest. Good thing the steps will go back there again!

Would you rather slow down your fading by keeping chlorine below 3ppm or not have an algae bloom? That's really the choice. Truly, you are better off concentrating on keeping the water sanitary.

BTW, that 3ppm is nonsense--the pool liner company cites it because the EPA says that's the max swimming water should be for safety. Recommending higher levels than that may introduce a legal liability so that's all they'll say. Curiously, the same agency (EPA) says DRINKING water can be 4ppm, and even, under certain conditions, as high as 10ppm. So somehow, magically, it's safe to drink water that it's not safe to swim in....

[kjsmom]

Thanks Carl,

Yeah, I know the liner will fade over time -- I'd just like to keep the liner new looking as long as possible!

This statement confuses me though:

"Chlorine levels at 15ppm with no CYA will fade them faster, that's all."

I understand that the CL will fade the liner; what affect does "no CYA" have, other than the CL disappearing quicker? Aren't the CL shocking levels lower w/no CYA?

Thanks for your help.
PAT

[mwsmith2]

CYA inhibits the action of Cl. Pools with high CYA can go higher with the Cl and not have adverse effects on the liner.

Michael

[kjsmom]

Thanks again, Michael --
Every time I think I'm about to figure it all out, I learn something brand new about which I was totally clueless. I had absolutely no idea cya protected the liner from high chlorine levels.

So, since I kept my CYA around 30, and I shocked my pool at 12-15 ppm, could that be why my liner faded?

PAT

[mwsmith2]

The primary job of CYA is not to protect your liner from high Cl levels. It just happens to do so because it inhibits Cl action when it is present in significant quantities, as mentioned before in this thread. Your liner most likely faded due to age, as mentioned by CarlD, a few posts up. If I remember correctly, most liners can take 15 ppm with no problem, but that is the upper limit. Other liner pool owners may remember better than I.

Michael

[kjsmom]

Thanks Michael,
I understand about the cya. There was discussion in the "old" forum that a vinyl liner could take 15 ppm, and I did go that high last Spring in an effort to speed up clearing the water. I know liners do fade over time, but mine was only 2 years old, which I thought was pretty new.

Anyway, I have a new liner, (due to disastrous encounter late last summer with an umbrella during a storm), and I'm going to try to be more conservative with the chlorine. I'm going to try the 60-80 cya and 1-3 ppm cl called for in the Aquarite manual.

I am a little nervous about that because according to the "best guess" chart, 60-80 cya requires a minimum FC level of 5ppm. Maybe the numbers are different with the SWC (I hope).
PAT

[waterbear]

I have an aqulogic SWG and run my cya at around 80 ppm and my FC at 3 pm and have had no problems so far.