Stubborn Yellow Algae

Yellow algae can be stubborn. Have you checked phosphates and CYA levels?

Bleach isn’t the issue, it's all we use here in Florida.  Yellow algae is resistant to chlorine so you have to use yellow out or something similar.  Phosphates could be part of the issue but most of the time it's bad runtimes and filtration that allow this issue to pop up.  How big is this pool and how much is it being used?

I would hit it with an algaecide, phosphate treatment, and then get a new filter installed afterward.  If this pool is larger and uncovered then running it 14hrs or more would be a good move in the summer.  We use “no more problems” the first week of every new month, especially in the summer months as a preventative.  Works very well to keep things like this from happening. 

Also have to say this, you also need to make sure the tech isn’t or hasn’t been taking shortcuts during service that would have led to this situation.  Not saying they weren’t doing everything but you have to rule that out as well.  

As stated above, it is resistant to chlorine, but you can get ahead of it. Thankfully we don’t deal with it much, but when we do, we triple shock with cal-hypo and thoroughly brush the entire pool. The yellow algae will suck the chlorine out of the water quickly. Return every day and repeat the process until the chlorine level holds. It usually takes us 3-4 days but could be longer based on the severity. 

Checked CYA but not phosphates… Will be checking that this week. 

Thanks for the thorough response! We have been using Yellow Blast by Regal each week for a few weeks. Going to check phosphates this week. Pump is brand new and set to run 13 hours I believe. Will also have to check on the filter because even though we clean it regularly I’m not positive when it was last replaced. 

Seems like my most likely culprits are the filter and phosphates. Thanks again guys! 

ABSOLUTELY recommend PoolRx! We have it in about 70% of our pools. We roll it out every spring when PoolRx has a generous rebate going on. They last 4-6mo which covers most of the season. Maybe 5% will need a booster. Any of our pool that have a recurring algae issue, we require they get a PoolRx. It is a time saver, and has many benefits other than algae preventative. It works on all algae including Black Algae. You will never have to worry about phosphates!

have you checked/treated for phosphates?

If you like podcasts, I listened to a great one on PoolNation where they explained the various types of algae and the best ways to address them. Overall it was very informative and I liked how she explained everything with visual explanations. 
 

They also have a more in depth version on their PoolMan University site.