Pitting on liner

[richierich]

Hi All - There's various spots in my 6 year old liner that have become sort of pitted and rough. I took an underwater picture, look toward the bottom right. Is this a sign that the liner might fail and should be replaced? Also the top of the liner is starting to fade in spots to white. The differences from last year to this year are 1) My FC is more consistent at about 11 now that I just put in a SWG and 2) I'm using a 2 speed pump on low a lot and not sure how well the water is moving around. Thinking maybe the Chlorine is just sitting at the bottom of the pool? Could be wrong. Maybe it's high calcium since I was using a lot of cal hypo last year before the SWG? My numbers are also as follows
FC - 12
CYA - was 40 bumped to 60 a few days ago
PH - was 7.8 lowered to 7.5
Calcium - 250
TA - 70
Salt 3800

 

[VinnyinNJ]

First, I want to say that I'm no expert!

Assuming you are using one of the recommended test kits ... Some things I see but I may be wrong - FC seems a bit high ... if the CYA was 40 and you're running FC at 12 that may be a reason for bleaching. Your CH is in the middle of the scale and your pH was/is in the high 7's - that pitting may be calcium coming off the plates. Salt of 3800 - I think this is a little high but I don't think it adds anything to bleach or pit.

Seeing how you used Cal Hypo that is probably why chlorine may sitting at the bottom of the pool, I used Cal Hypo years ago and I think I added it to the skimmer basket (didn't have a SWG - wasn't worried about any issues). Going forward with the SWG it doesn't matter how fast the pump is going assuming it is going fast enough for the SWG to work if it has a pressure switch. Also going forward try to use liquid chlorine or plain old bleach with nothing added to it and pour it in front of the return.

What should happen if you winterize your pool including lowering the water is that removing in the Winter and adding water in the Spring will lower most of your added chemicals depending on what the tap water consists of.

Hopefully someone with more knowledge will come along and be more helpful.

 

[richierich]

Interesting thoughts. Maybe you're right. Worried about the liner maybe being in danger of failing since it seems slightly brittle in those pitted spots. Yeah I do lower my water so then the Calcium should get lower as well. I'll stop using cal hypo. Maybe I should have posted in the chemicals forum also

 

[kellyfair]

Your FC is high for the CYA you are running, and your CYA isn’t high enough - for a SWG, you should be around 70, and shoot for around 6 or 7 for FC. You don’t need the cal hypo now, and your CH doesn’t seem excessive.

 

[duraleigh]

By far, the most common build-up on vinyl lined pools is calcium scale. The liner itself really can't be "pitted" because it is so thin but scale can form on it and give the rough appearance and feel of pitting.

Lower the pH down to 7.0 and keep it there for four or five days. That may loosen the scale. You can brush daily,too, just not so vigorous as to rip the liner.

As always, manage your chlorine according to the FC/CYA chart during this process.

 

[richierich]

By far, the most common build-up on vinyl lined pools is calcium scale. The liner itself really can't be "pitted" because it is so thin but scale can form on it and give the rough appearance and feel of pitting.

Lower the pH down to 7.0 and keep it there for four or five days. That may loosen the scale. You can brush daily,too, just not so vigorous as to rip the liner.

As always, manage your chlorine according to the FC/CYA chart during this process.

If I drain some of the water to lower the Calcium will that break it up as well?

Since my CYA is now 60 I guess I need to target like 7 FC. Not the 10-12 I had as well.

 

[duraleigh]

If I drain some of the water to lower the Calcium will that break it up as well?

No. you need to lower the pH and keep it low.

 

[richierich]

No. you need to lower the pH and keep it low.

Ok thanks. Will add some acid and keep it lower for a few days like you suggested then brush gently? Once it's removed what level should I bring the PH back up to?

 

[richierich]

Also - is calcium scaling potentially dangerous for the liner that it can possible rip or tear or leak?

 

[duraleigh]

Can you scrape off a little piece of the scale? If so, put it on a board and drop a drop or two of muriatic acid onto it. It should fizz up pretty good........confirming it's scale.

I doubt it is harmful to the liner but you don't want it there. Because you have shown a tendency to scale. I would keep pH from 7.0 to 7.4 and that should prevent it from coming back.

 

[richierich]

Can you scrape off a little piece of the scale? If so, put it on a board and drop a drop or two of muriatic acid onto it. It should fizz up pretty good........confirming it's scale.

I doubt it is harmful to the liner but you don't want it there. Because you have shown a tendency to scale. I would keep pH from 7.0 to 7.4 and that should prevent it from coming back.

Thanks - will give it a go.