Does chlorine kill established black algae?

[max2k]

Good morning to everyone,

I believe the black stains are copper stains, not black algae. Two words: pristine blue. Chief of Staff starting using that product line unbeknownst to me and the day after she added "lithium something" the stains showed up.

Here are my numbers from this morning:

FC- 4.8
CC- 0.6
PH-<7.0 (tested several times)
CNA- 90-100
TA- 110
CH-350 (tested several times)

I tested my FC last night at sundown, it was 9. This mornings test was after sunrise but before and direct sunlight hit the pool due to tree shade. Something is eating my chlorine.

Standing by further instruction.

Thanks

If I understand you correctly CNA is Cyanuric Acid. If so it goes by abbreviation CYA around here, try to switch to reduce confusion.

In general, you need to go through SLAM where you'd bring FC concentration to higher than normal level and keep it there by often additions until whatever is in your water stops consuming FC. Unfortunately, your water is not in the best shape to start the SLAM at the moment, it would be the best to perform partial drain first.

It would achieve 2 objectives:
- partially get rid of Pristine Blue in your water
- bring down CYA to more sensible level so you won't need very high FC during SLAM.

Before you drain though you need to add sequestration agent to pool to lift copper back to water so when you'll be draining you'll be getting rid of it efficiently. Jack's Magic is recommended brand around here but my expertise in metal staining is very limited; hopefully someone else will comment on that. So general plan is:

1. Bring your FC to 10-12 ppm using liquid bleach or you risk pool turning green very soon. This is just for you to be able to 'hang in there', not really to fix anything.

2. Add copper sequestration agent

3. Drain 50-60% of water in 2 - 3 runs. Please find out how high is your natural water table. In rare circumstances when water table is high and significant portion of pool water is drained the entire pool can float out of the ground leading to extremely costly repairs. At the end of this step you need CYA to be in 30-40 ppm range.

4. Perform SLAM.

Please do not add anything to the water unless advised from this forum or we won't be able to figure out what is going on at the end. Please use only liquid bleach as source of chlorine. No 'shocks', tablets, pucks or other forms of solid chlorine as it will bring additional CYA into the mix.

 

[poolbrush]

Max,

Corrected CNA to CYA

I don't have a main drain due to it being capped off due to leak somewhere between bottom of pool and pump. (We have operated that way for at least 10-11 years.) Additionally, I have to fill with 2 garden hoses off the house.

I need water line above skimmer line in order to circulate the bleach and copper sequestration agent, don't I? I have 1 1/2" skimmer line and 1 HP pump.

I have positioned a sump pump in pool that will discharge about 3000 gallons/hour. Good call on water table concern but I am sitting on a high spot that is almost sandy in composition. My pool wont get dislodged.

Initially I was going to drain about 30% on one run (about 4 hours) and then refill. Sounds like that will work after I add copper sequestration agent and some chlorine.

My water has had the black stains for about 10 days and the water is clear and blue this morning. I believe the Chief of Staff added Pristine Clean (metal control for pools) could that be helping keep it "pristine?"

For right now I will add adequate amount of bleach and jacks magic and then empty 10,000 gallons and refill and retest. Off to wal mart and "the pool store" Puh-tooey!

Thanks

 

[max2k]

you learning very fast and very soon won't need anyone's help .

From my reading of other threads I understand metals inhibit algae growth. I don't think they're worth the risk of subsequent fight with stains. The biggest problem with those 'systems' is much more serious but also less visible- they don't kill everything else besides algae, at least not as fast. I'd rather have unsightly green water which is sanitary than clear one and catch something from it. Chlorine kills pathogens at lower FC than algae so if algae is gone in chlorine sanitized pool everything else has died well before that. This is not true with metal- controlled pools: you can have algae free water which 'looks' clean but it is not sanitary to swim in. Granted this situation is very rare in private pools but why ask for trouble?

 

[poolbrush]

I have drained out about 10,000 gallons and was considering a refill overnight. However, after draining, some of the stains on the steps (see pics in previous posts) were exposed by the low water level and were cleaned up instantly with lemon juice (the kid at pool store said to try that when I balked at the $50/qt stain remover {absorbic acid}used at double strength)

Seeing remarkable results gained by simple lemon juice, I am inclined to continue to drain pool water level down to about 50% and might be able to clean most of the stains with a lemon juice saturated mop/sponge. Also this will help me get the aforementioned goal of reducing CYA and CH.

 

[max2k]

I have drained out about 10,000 gallons and was considering a refill overnight. However, after draining, some of the stains on the steps (see pics in previous posts) were exposed by the low water level and were cleaned up instantly with lemon juice (the kid at pool store said to try that when I balked at the $50/qt stain remover {absorbic acid}used at double strength)

Seeing remarkable results gained by simple lemon juice, I am inclined to continue to drain pool water level down to about 50% and might be able to clean most of the stains with a lemon juice saturated mop/sponge. Also this will help me get the aforementioned goal of reducing CYA and CH.

there's this concept in chemistry that things don't disappear without trace: your stains will be removed but unless you collect the product of reaction and flush it out to drain somehow the copper will be still there, just in different form waiting to fall out from water again. That's what I hate about it- there's no easy/sure way to get rid of it for good, like turn it into insoluble dust which can be filtered out.

I think you understand the main idea: if you can arrange washing out of the 'disappeared' stain like rinsing cleaning sponge in a bucket which you'd flush down from time to time during this process you'd do yourself a huge favor. I also expect plaster to react with lemon juice so try to rinse it with fresh water after getting rid of the stain or better yet- with backing soda solution to neutralize remaining lemon juice acid.

 

[pooldv]

Then this process would probably work.
Ascorbic Treatment to rid Pool of metal stains

 

[max2k]

Then this process would probably work.
Ascorbic Treatment to rid Pool of metal stains

If I'm not mistaken The Ascorbic Acid Treatment will leave copper where it is - in the water which is acceptable when you can't drain. If my understanding is correct OP has unique opportunity to get rid of it for good because he is able to access stains 'dry' with the sponge due to his partial drain.

To poolbrush: whatever you do don't leave plaster exposed to the Sun for too long, it might dry and crack. You probably can keep it wet with garden hose. Besides drying out it can get heated up higher than your normal water temperature and that could cause cracking due to temperature expansion. I personally leave my spa exposed to the Sun only for minutes when I'm cleaning it and still splash it out to keep it wet.

 

[poolbrush]

there's this concept in chemistry that things don't disappear without trace: your stains will be removed but unless you collect the product of reaction and flush it out to drain somehow the copper will be still there, just in different form waiting to fall out from water again. That's what I hate about it- there's no easy/sure way to get rid of it for good, like turn it into insoluble dust which can be filtered out.

I think you understand the main idea: if you can arrange washing out of the 'disappeared' stain like rinsing cleaning sponge in a bucket which you'd flush down from time to time during this process you'd do yourself a huge favor. I also expect plaster to react with lemon juice so try to rinse it with fresh water after getting rid of the stain or better yet- with backing soda solution to neutralize remaining lemon juice acid.

Ahhhh, The Law of Conservation of Mass: matter is neither created nor destroyed.

I would have to drain 80% of my pool to get the stains exposed to air. I don't want to do that because of the fill time required. I didn't realize plaster was so sensitive to sunlight.

Additionally, I think my plaster is shot (started new thread: Judging the Status of Plaster in TFPC method section) So, if we are gonna have to replaster, I don't want to waste a lot of time and water cleaning the copper stain.

So onward with another couple of days of draining and refilling to get water back in shape to swim in for rest of season. I'll report back when I'm ready to SLAM.