Black Algae (I think) on water line of Pebble Tec raised Bond Beam

[lmahoney]

Hello! This is my first post on this site so hopefully I will give the correct information and background in order to get some help with a potential algae problem I have. I just moved into my house about 4 months ago and the house had a pool that was built in 2008. The pool was in good shape and with just some TLC with cleaning I was able to get it looking great and chemicals balanced. Over the last couple weeks the temperature has drastically increased here in Arizona and I noticed by Acid level was down. I added acid a couple times and its now great and balanced. Unfortunately last week I noticed a black line forming on my pebble tec rolled bond beam. I've attached a picture. Can I get some suggestions on how best to get rid of it? Thank you!

 

[Texas Splash]

Hello and welcome! It's always possible the black you see may be something other than algae as well (i.e. scum line). Do you only see this discoloration at the water line? I know you mentioned the water was balanced, but can you post a full set of results from your TF-100 or Taylor K-2006 please? That will help. Thanks, and nice to have you with us.

 

[lmahoney]

Thank you for the reply. I actually only have a basic kit so I can take my water to the local pool store to have it fully tested and post results later today. In regards to the location, yes it is ONLY at the water line. I do not see a build up or discoloration anywhere else on the pool. I will post the test results soon for you to see. Thank you!

 

[Texas Splash]

A scum line sometimes presents itself along the rim or waterline of a pool as oils and such wash-up against the edge - hence the scum line name. It can happen in even the most perfect of pools. Occasionally when it happens to me, I'll use a small scrubby-pad and/or Magic Eraser and it comes right off. You might also try a simple bleach/water solution and brush to see if that works.

As for your water tests, there's no need running to the pool store on our account. We'll only remind you of how we don't place a lot of faith in pool store tests. Your best option is to purchase your own test kit, and we recommend the TF-100 (link below) or Taylor K-2006. Either of those kits perform all the testing you need, and most importantly, it will be accurate. I believe the TF-100 is a better value, but either one performs all the tests you need for a great swimming season.

Good luck and let us know how things turn out.

 

[lmahoney]

Thank you for the good information. This black line is only on the pebble tec bond beam so I'm concerned about how to actually scrub it off. I have a wire brush that I've just tried to scrub it with but doesn't seem to work. Should I try to spray on a bleach/water mixture and scrub it again? I also have liquid chlorine, would that also be worth trying with the wire brush?

 

[Texas Splash]

(Regular) bleach and chlorine are the same (Sodium Hypochlorite), so yes you can do a 4/1 ratio mixture of water and bleach and try it. You could even go stronger if you wanted - maybe 50/50. If that doesn't work, we may consider a 4/1 ratio of water and muriatic acid with some gentle scrubbing. Both are products used everyday in our pools so it's fine for the water and surfaces.

 

[lmahoney]

I just sprayed a small section of the pool water line with the liquid chlorine mixture and scrubbed a little and it worked! The black scum is definitely coming off! It's going to take a bit more elbow grease when it cools down outside enough for me to handle it but so happy this solution is working. Thank you so much for the help and will definitely be coming back to this site to post other comments or questions I might have in the future. This definitely saved me money in unneeded pool chemicals. Thanks!

 

[Texas Splash]

Outstanding! Glad it worked. Have a nice evening.