Chlorine Resistant Algae?

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M

mdenbow

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Jun 13, 2015
19
Apple Valley, CA
I've gone and done the unthinkable; did a complete drain and refill of my AG pool in a drought area. :evil: I've had it fighting a constantly green pool. Especially when I don't fully understand why algae loves my pool so much. Here are my chemistry results while I had a green pool and before I lost my patience and drained it.

FC: 38
CC: .5
pH: 7.6
CH: 62 (sort of irrelevant since I have an AG pool)
TA: 162
CYA: 180

Even with the above results, the algae was having a party in there; alive and well and a beautiful shade of green. I know a large part of the problem is my high CYA level. It's an unavoidable consequence of using di-chlor tablets over time. Two weeks ago I had my house painted and forgot about my pool for 4-5 days and naturally it was a swamp. So I shocked it with 4 bags of lithium hypochlorite and the next day the green was gone and after another week of filtering I had just about cleared the cloudiness, when one day I notice dirt on the bottom with green under it. I checked the FC level and it was 14.5 and ran my pool cleaner to clean out the dirt and left for the day. When I returned, the pool was a cloudy, green mess. So I shocked it again with 5 bags of lithium to a FC of 48 and filtered all night. The next morning the pool looked exactly the same as it did the day before. That's when I lost my patience and just drained it and refilled it. According to the pool math tool, at a CYA level of 180 my FC level needs to be 14-21 with a shock level of 71. I would need at least 12 bags of lithium shock to achieve that FC level. I can't afford to be putting $100 a week worth of chlorine in there just to keep the green out. So my question is: did I do the right thing by draining and refilling to get rid of the excess CYA and then throwing away the di-chlor tablets and switching to liquid sodium hypochlorite?
 
I get it. I think you did the right thing.

Until the pool gets up to the skimmers, why don't you put 1/2 gallon of Clorox in your pool this evening.

Once your pool is filled halfway up the skimmers. Run your pump for maybe 30 minutes and then take a sample from maybe a foot deep in the pool.

I like to take that sample inside and test sitting at a table. However you do it, please give us a complete set of test results.

Your CYA should now be zero or so close to it you can't measure it. That not a bad thing!
 
how do you measure those high level of FC? Dropping 76 drops into 10mL sample or diluting it first?

If diluting you need to mix the sample and pour out mixture excess so it remains at the required level (10 or 25 mL). Please also test the water you use for diluting as it needs to be free of chlorine, etc. Distilled would be the best but I used my local tap water as it is sufficiently clean. When my CYA was at 300 I used this trick every time and my multiplier was 2 ppm after 1:3 dilution. Thanks to this site I never had a green mess on my hands even though CYA was off the charts.
 
max2k said:
how do you measure those high level of FC? Dropping 76 drops into 10mL sample or diluting it first?
Click to expand...

Yes, I added a whole lotta drops. Tap water does have some chlorine in it so I didn't want to dilute with that and throw off the result. Distilled water is a good idea though. What I got so fed up with was even though the FC is at levels you probably don't want to swim in, the algae still thrives in it. I'm pretty sure the high CYA level is hindering the chlorine's affect. I've never heard of anyone having to keep their FC level at >20ppm all the time just to keep their pool clear. That's what I've been having to do.

Duraleigh, are you referring to 1/2 gallon of household bleach or regular pool store liquid sodium hypochlorite?
 
Finished refilling. Post fill chemistry:

FC: 4
CC: 0
pH: 7.8
TA:80
CYA: <30 (The K-2006 CYA test only goes down to 30. I can still clearly see the black dot at 30, so I don't really know what the CYA level is)

As I write this, pool is is sparkling clear and beautiful. I will recheck the FC later this afternoon to see how it's holding up. Any recommendations, please advise.
 
mdenbow said:
Finished refilling. Post fill chemistry:

FC: 4
CC: 0
pH: 7.8
TA:80
CYA: <30 (The K-2006 CYA test only goes down to 30. I can still clearly see the black dot at 30, so I don't really know what the CYA level is)

As I write this, pool is is sparkling clear and beautiful. I will recheck the FC later this afternoon to see how it's holding up. Any recommendations, please advise.
Click to expand...

if the pool is under direct sunlight I'd bring CYA to 40 and maintain FC at 5- according to the chart. May be bring down pH a little- depends where it tends to go on its own. Basically, maintenance stuff- you need to perform these tests daily at the beginning to get a feeling how fast those numbers change as each pool is unique. Then once/twice a week would be enough.
 
max2k said:
if the pool is under direct sunlight I'd bring CYA to 40 and maintain FC at 5- according to the chart. May be bring down pH a little- depends where it tends to go on its own. Basically, maintenance stuff- you need to perform these tests daily at the beginning to get a feeling how fast those numbers change as each pool is unique. Then once/twice a week would be enough.
Click to expand...

The pool is in full sun most of the day. I'm a little gun shy about adding cyanuric acid now. I'm adding a little at a time to try and sneak up on 40ppm. I threw away the di-chlor tablets I'd been using. I've been using liquid sodium hypochlorite 10% solution, keeping the FC between 3-5ppm and my pool has been beautifully crystal clear. The pH has drifted down to around 7.4-7.5. I also replaced the filter element in my Hayward cartridge filter which really helped the circulation. I guess most pool owners need to refresh their water every couple three seasons because after adding this and that to it to correct one problem or another, it eventually turns into a chemical soup that just needs to be drained and discarded. Accurate statement? Thanks for the help.
 

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