Algae Bloom

[cschnurr]

Every year, end of July-early August I get an algae bloom

This year is no exception.
I have an AquaRite a SWG system and this year maintained Cl above 5.
Pump ran 12hrs /day.
Last week pool started turning slightly. I increased the pump to run 24/7, and added clarifier.
I vacummed up the next day, then went on vacation for a 4 days.
Upon return, I have large deposits of green/yellow looking algae.
When I turn the SWG off at night, I do not drop Cl

My measurements are below:
FC=5
TC=5
pH=8
TA=100
CH (not measured)
Salt=3800 (Test Strip)
Salt=3200 (AquaRite Meter)

I ran out of CYA reagant, so I went to the Pool Store where I buy my liquid Chlorine, and asked them to measure it.
They measured

CYA=100
Salt=2900

I did not believe their CYA measurement, as I had monitored this earlier this year.
So I bought some Taylor CYA reagants at the store. When I came home I measured CYA as 50.
So I went back and asked the PS to remeasure using their system (I think it was called True View 2).
I then had them measure the same sample with the Taylor reagants they just sold me.
They confirmed the discrepancy, but without any explanation.

So I went to another PS.
They measured
CYA=40
Salt 3500.
The rest of the measurements were reasonably similiar.

Q1 Why do I have a cloudy pool, if my Cl hasn't dropped below 5, my CC=0, and my FC doesn't drop overnight?


Q2Can anyone explain
a) CYA ranging between 40 and 100. (250%)
b) Salt range from 2900 to 3800. (30% error)
I know everyone on the forum recommends to trust your measurements, but how can this variation be possible.
Since I'm having this problem annually, I recognize I must be missing something. CYA measurement error seemed like a probable cause.

Here is my plan to treat the pool.

a) Shock pool to Cl=29 (assuming mustard algae and CYA of 50)
I don't have an FAS/DPD, so I will calculate from the pool volume, and I'll measure using the dilution factor of 10:1, which makes it just a bit better than meaningless
b) Vaccuum pool
c) Add algaecide Polyquat 60, vacuum again.
d) Once cleared, I'm going to try some filter cleaner that I was sold, but I remember some discussion about it on this forum.

PS recommended I use alaecide instead of shock, but I decided against it. (Algacide instructions indicate this could be done)

Any other recommendations or comments would be helpful

 

[dmanb2b]

are you sure you don;t have high CH? PH above 7.8 could be causing calcium scaling.

I recommend you lower your PH to the 7.4-7.6 range before shocking

 

[duraleigh]

Q1 Why do I have a cloudy pool, if my Cl hasn't dropped below 5, my CC=0, and my FC doesn't drop overnight?

Chlorine kills algae......that's inescapable. Adequate levels of chlorine in your pool at all times will ensure that you will not get algae.

If you are getting algae, then despite whatever your test results say, you have inadequate chlorine in your pool. Increase the chlorine level in your pool and you will not get algae.

As for the variances in the tests, You have read the hundreds if not thousands of posts of inadequate testing by pool stores......they simply can't do it right.

1. Get yourself an FAS/DPD chlorine test

2. Replenish your CYA reagent.

3. Per the manufacturer's advice, run the CYA in your pool up in the 60-80 range. That's where you should be with an SWG.

4. I mentioned the CYA last because I don't want to detract from the importance of adequate chlorine.........that's causing your algae blooms. The CYA will simply allow your SWG to not work so hard.

 

[anonapersona]

Are you getting adequate circulation?

 

[cschnurr]

Thanks for your replies

I reread the sticky on getting rid of algae and am following the regiment.
It implies that CYA measurements may not be reliable during periods of algae.

The sticky refers to dead algae. It was my understanding the dead algae was 'white/grey', but in a couple posts some have stated that this may not always be the case.

I have dropped pH to ~7.4.

This will be the first year I use Mustard Shock level, previous years I've just used Shock Level.
1) What does 'Yellow Mustard Min' mean in chemgeeks Chlorine/CYA chart.


The water has turned from greenish to grey/white, but I'm still getting some algae deposits forming on the bottom. The first couple times I vacuumed to filter and then backwashed immediately. I did this to conserve water as I would have taken a couple hours of refill water.
2) would it have been better to brush

The deposits are getting smaller during the shocking process, so now I'm either vacuuming to waste or brushing.
3)Is there a preference