The green algae never goes away!?

[Pmchick]

I have a pool where the levels are well maintained:
FC=3.0 on a regular basis
pH=7.4
Alk= 105
CH=290
The problem is that green algae grows in the seam of the pool(this is a plaster pool) and on the corners of the steps. The FC is maintained at a 3.0, the pool is brushed w/a metal algae brush once a week, there is good circulation, I don't get why it keeps growing back!
The whole pool doesn't turn green, it's just in certain spots. Even with shocking the pool and bring the FC up to 20ppm-it still comes back!
This is a pool that I had inherited 4 months ago, the previous person who "maintained" the pool did not keep up with the chemicals, or basic maintainance proceedures. The pool also hasn't been drained in 2yrs.... Could the only way to combat the algae be to drain & acid wash the pool?
Liquid chlorine is used and there is no CYA-this is an indoor pool with a retractable roof.
Any suggestions to beat the green algae growing in my cracks?
Thank you

 

[257WbyMag]

The key to beating algae is shocking, brushing (lots), and continuing the process until your FC holds for a period of time.

Are those test results your numbers from your kit or did you take a sample to a pool store?

You mentioned that you have no CYA in the water because it is an indoor pool but that you have a retractable roof over the pool. If you retract the roof, allowing sunlight to hit the pool water, even for a little bit, you can lose your FC very, very quickly. Perhaps you opened the door to an algae bloom by leaving the roof retracted at some point? With a retractable roof, it might be advisable to run a minimal amount of CYA in the pool to hold some FC in reserve. As it stands now though, you need to shock and brush until you can hold your FC in the water.

 

[frustratedpoolmom]

Yes, increase the CYA to 20-30 as suggested previously. 3 is a little too high for an indoor pool with no CYA.

How often are you running the pump/filter? What can occasionally happen is "FC dead spots" -this can be localized areas where the FC is consumed and the water circulation poor (like steps) and unless the water is circulating properly they can easily develop. Sounds like that is what is happening here. You may need to try increasing the filtration time to keep the FC circulating evenly through out the pool.

Try brushing these problematic areas - more often if possible, until you find your ideal run time.

Is the FC holding overnight, for you to determine if you are done shocking?

And when the FC is "maintained at 3" are you adding bleach in the evening, testing 1-2 hours later to confirm you are in fact, reaching your target of 3, and then testing again first thing in the morning to see if the 3 is holding?

 

[Pmchick]

Yes, I am testing with my own test kit, the LaMotte ColorQ. I do test the water every 2hrs & the pump is running 24/7. Maybe that is why the algae keeps blooming, I'm not 100% sure the the FC is holding over night.....
How can I add CYA to the pool? I have a chemical controller-the AK-100, the sanitized is automatically fed into the pool.
When I shock, I use 65% cal-hypo ....
Although, I do notice that the algae blooms almost dead center in the pool....perhaps I have a "dead spot" there?

Thank you for your help with this issue, I'm going to try & do another shock this weekend...and brush more often. Do you think that I should drain the pool, acidwash & start fresh?

 

[JasonLion]

Draining the pool and cleaning everything might work for a while, but it doesn't really solve the problem in the long run. The algae will just come back unless you figure out what you are doing wrong.

Something is wrong with one of your assumptions. If there really wasn't any CYA in the water, an FC level of 5 would kill any algae. So either you have some CYA in the pool, or your FC level hasn't been 5 for a long time, or that isn't algae. If you have some CYA in the pool, you need to know how much, so you can shock to the correct level.

Since most of the FC tests are fairly reliable at measuring levels around 3-5, I think you must already have some CYA in the pool and haven't been shocking to a high enough FC level. The ColorQ is fairly reliable at measuring FC levels around 3, so that seems reasonably certain. As for not having algae, some people mix up pollen with algae, but pollen shouldn't be an issue in an indoor pool.

 

[frustratedpoolmom]

I'm not at all familiar with the ColorQ - how high does this test read for FC? Does it test CYA?

(to add CYA -if you are 100% positive its not already present) :
you purchase it from a pool store, use the pool calculator to determine the appropriate dosage and then you can put it in a sock, like any old sock, and tie a knot in the top, and then set the sock to the side in the skimmer, so the water still flows freely. The CYA will dissolve out of the sock and after about 5-7 days you test the CYA level again (it takes that long to fully register on tests.)

I agree with Jason - draining/acid wash really won't accomplish what you need. Don't worry, we'll help you get this figured out. How many gallons is the pool, how big is the pump and what size/type of filter do you have?

 

[JasonLion]

I'm not at all familiar with the ColorQ - how high does this test read for FC? Does it test CYA?

The ColorQ can measure FC and CC up to 10. It can also measure CYA levels, but is noticeably less precise in it's CYA measurements than the usual black dot test (which isn't all that good to begin with).

 

[Butterfly]

I'm going to try & do another shock this weekend...and brush more often

Just want to make sure that you understand that shocking your pool is a process and not a one-time event.

Once you start the shock process, you should maintain shock levels until you pass the 'tests' that let you know that you are done shocking.

Pool School has a detailed How to Shock Your Pool article.

Also, I suggest you retract the roof during the day while shocking to let the sunlight help destroy CC's.

Good luck and welcome to the forum

 

[frustratedpoolmom]

Also, I suggest you retract the roof during the day while shocking to let the sunlight help destroy CC's.

I agree, IF your CYA level is 20-30. Otherwise the sun will consume the FC.

 

[Pacifica]

Increase the CYA to 30 ppm and make sure that your filter has no holes in your grids if its DE and no tears in the cartridges if its a cartridge filter. The best algaecide that I have used is the Algaecide 60. It doesn't eat up chlorine and will keep a residual in the water for about a month if you dose your pool as directed.