Waterline stains - algae or something else

[consigliere08]

Hello everyone! I'm new to the forum, really looking forward to sharing experiences with other pool owners. Since I'm from Europe (Serbia), i noticed that most of the members are from US, I'll try to use both units of measurement just to avoid confusion.
For the last 3 years i had a Polygroup pool 3.05m x 0.77m (10'x30") and this year i upgraded to Bestway Steel Pro Max 4.57m x 1.22 (15' x 48"). I've already started preparing and leveling the ground so that everything comes settled before the start of new swimming season.
Everything was fine with the previous pool, except that after the first year i noticed green and bleached waterline stains. I always followed all the instructions; first of all, i would wipe the liner with algaecide before filling the pool (not sure it is necessary?), after filling i would correct the Ph (since the Ph of the water in the city is higher than 8ppm), shocking it with chlorine, correct the Ph again and finally do a algaecide shock. I mantained it all during the summer season, after which i would empty the pool and put it away until the next summer.
Since i bought a brand new pool, i would like to avoid the appearance od these stains. Even when i tried to scrub it away, it wouldn't come off completely.
I'll post photos so you can see what it looks like. Besides that, the water was crystal clear all the time. It looks like algae to me, but I'm not completely sure.

 

[Texas Splash]

Welcome to TFP! Here in the U.S. we recommend pool owners test their water with a TF-100 (link in my signature) or Taylor K-2006C test kit. Unfortunately for you, having either of these shipped to you may not be an option. The availability of chemicals in your area also can be a factor. So what I would first recommend is that you spend some time looking at the various articles from our Pool Care Basics. Many of the items recommended here at TFP are on that page and can be very helpful.

The ring around your waterline area looks like a scum line, or perhaps some sort of organic stain. If you can get a Magic Eraser locally, or perhaps try a diluted bleach & water mixture with a scrub pad, it might help.

Please take a look at that link and let us know what else we can do to help answer any questions. Enjoy the forum.

 

[consigliere08]

Thank you. I spent last few days reading some of the articles.
Unfortunately, they do not ship TF-100 to my country. The only similiar option i can get here is a digital tester (a bit expensive toy) that measures free and total chlorine, pH, alkalinity and CYA. Currently I'm using drop test kit for chlorine and pH.
I tried Magic Eraser last year, first it looked like it might work, but eventually it wouldn't come off completely.
Since I won't be using that pool again, what can I do to prevent scum line/organic stain to appear on a new one? I suppose i should test my water alcalinity? I had problems with high pH, since my water gets really warm from mid-season, sometimes i had to lower pH almost every second day. However, i just learned here that I should've used muriatic acid for lowering pH instead of various 'ph minus' products.
This year the plan is to make a misting system around the pool to improve aeration, hopefully that would help to cool down water temperature a bit. Just trying to figure what's the cause of these stains.

 

[Texas Splash]

what can I do to prevent scum line/organic stain to appear on a new one?

As long as your water has no metals in it (typically iron), then it's mostly a matter of maintaining the proper levels. See link below. Of course this is where accurate test results become so critical. Also be careful about the products you add to the water. In some countries, the products available may have side effects. They may or may not have a good ingredients label.

What Are My Ideal Pool Levels?

Use our tool to find ideal chemical levels for any swimming pool. Check TFP recommended levels on pH, free chlorine, cyanuric acid, and more.

www.troublefreepool.com