Recurring algae - First algae experience slamming- Confused

[midijamm]

Just recently took over caring for a pool (care taking estate)
The pool company was doing it and I watched what they did for some time before I volunteered to take over. They came once a week and poured some chlorine and acid in and ran their Hammerhead that made it all cloudy and that was it.

I found this site and got a K2006 kit and found that there was almost no calcium, the TA was extremely low and 0 CYA

but there was never any algae problem while they maintained it. After I took over it bloomed yellowish green. I slammed it for three days and it got crystal clear. Then I made sure that the FC level stayed between 3-5 but in a few weeks it started to get green again.

I don't understand what is going on. I thought if the Chlorine level stayed up at all times this could not happen.

Because the CYA was at 0 I used the tricolor tabs exclusively for chlorination and Taylor FAS-DPT kit was daily assuring me the levels were good

Now I'm back slamming and am also confused about the proper slamming level. In one place it read 12 PPM, in another I read 20-30 PPM. I have been going for the 20-30 level but it would be nice not to have to use so much.
I see that it is relative to CYA content but am still confused
I think I have some CYA now (the dot almost,maybe,pretty much disappears at a full to overflowing tube) which would be 30

SO……..any suggestions/advice on PPM for slamming and explanations for the recurring algae?

TIA

Confused

BTW it's a 25000 gal tiled pool w/sand filter and ancient 1hp pump
I got the calcium up to 190 and TA up to 90 so far

 

[Azgirl71]

If you think your CYA is 30 then take the pucks out and SLAM to target level of 12-16 using bleach

 

[tim5055]

Welcome to TFP!

You say you SLAMed it for,three days, but did you actually complete the full SLAM process

You should have had clear water, less than .5 CC and pass an OCLT?

http://www.troublefreepool.com/content/136-perform-the-overnight-fc-chlorine-loss-test-oclt

I'm thinking you ended the SLAM a little early with low level algae still in the pool.

I'm surprised at the CYA levels if the people taking care of the pool just added powered chlorine once a week. Once the SLAM is complete you really need to get the CYA up to 40 or 50 in the keys or the sun is going to,cause that FC to drop during the day.

 

[Divin Dave]

Hi midijamm,
most likely the algae reoccurred because with CYA of 0, the FC burned off really quicly and wasnt sufficient for long enough to battle the algae. You are in FL where its sunny a LOT and that just exasperates the situation. The CYA protects the chlorine from being burned off by the sun too quickly. Without it, it's a loosing battle.

Leave your CH and TA alone for now. Lets get the water clean first.

OK, so you are at 30 CYA, thats good level for slamming.

The FC level is relative to the CYA. Its a percentage factor, which is why you see so much variation from one to another.

For Slam level, FC is 40% of CYA of 30, so,,, 30*.4= 12 > Slam level FC is 12ppm.
for regular maintenance, the FC target is 11.5% (and never let it get below 7.5%) but dont concentrate on that yet.


You want to lower your Ph to 7.2 before you slam.
After that, MAINTAIN the slam level of AT LEAST 12. The more you can keep the FC at 12 or a ppm or 2 higher, the quicker it will go. Thats means testing multiple times a day and dosing multiple times a day as required.

There are 3 criteria for completing the SLAM
1. Your CC is 1 drop or less to go clear (<.5)
2. You pass the overnight chlorine loss test (OCLT). Not more than 1 ppm loss
3. Your water is crystal clear

Even if you pass 1 and 2, you need to keep FC at slam until the water is clear.. that often is a day or 2 after the algae is done for..better safe than sorry.

Also, you need to backwash when the pressure rises 20-25% above the 'clean' pressure. This will help filter out all of the dead algae quicker and is just more efficient all the way around.

After the slam is over, you probably should raise CYA a bit due to your location.. at least 40, 50 would probably be better, and then keep your FC at a level relative to that.

Hope this helps.. please post up any more questions you have or something you dont understand yet. Thats why we are here.

 

[midijamm]

Thanks to all. You guys are great!

In reviewing all info I carefully reviewed the CYA testing method and discovered that I am doing it wrong (not in sunlight) and I do not really have any visible cloudiness in the sample/reagent so I need to add CYA. Since the smallest amount the K2006 measures is 30PPM I have no way to know exactly how much to add. I suppose i should shoot for a 20 PPM increase so as to not go over 40?

 

[Azgirl71]

Just add 1/2 the recommendation for now so you don't overshoot.

 

[Divin Dave]

just add half, and Im hoping you are using Pool Match to determine how much that is.
http://www.troublefreepool.com/calc.html

Thanks to all. You guys are great!

In reviewing all info I carefully reviewed the CYA testing method and discovered that I am doing it wrong (not in sunlight) and I do not really have any visible cloudiness in the sample/reagent so I need to add CYA. Since the smallest amount the K2006 measures is 30PPM I have no way to know exactly how much to add. I suppose i should shoot for a 20 PPM increase so as to not go over 40?