Can Kill Algae with low Chlorine Loss????

[dprosper75]

All,

Been using the BBB method for over 3 years and it has been a godsend. During all this time, I have never had an issue
with any type of green anything in the pool. However, something interesting is going on. I live in MD and of course
this weekend we got a ton of rain. The wife took me for an over night to Philly on Sat. So knowing, I wouldn't be around
to monitor the pool for a day, I boosted my FC to 11. (CYA is currently at 50ish). Sat had all day rain. I came back on
Sunday and peeked in the pool and saw a lil green at the transition from floor to wall. So as warm as it was yesterday (insert sarcasm), I got in the pool and brushed and there was more green on the transitions from floor to wall all around. So I brushed to dislodge it all and turn the pump onto high. Now the pool appears more milky (which should be a sign that
the algae is dead) but I don't seem to have lost any chlorine. I ran my numbers before I slammed and here is where I
was at: FC=9 CC=0 PH=7.3 CYA=50/55ish TA=100. I calculated for the pool (15600 gallons) to boost the FC from
9 to 20. It wound up being an FC of 24. At 6:44pm yesterday my FC = 24 and CC = 0.25. At 9:33pm, my FC = 24 and CC 0.25. This morning at 6:30am my FC = 23.5 and CC = 0.25.

I would have expected to have an FC that was much lower. Is it possible to catch the start of an algae bloom at the right time and kill it before it really gets started and don't lose much FC? Really confused on this one. I really expected to have to keep boosting the FC level to around 20 for an extended period of time.

Thoughts anyone??????

Thanks............
D

 

[Texas Splash]

The fact that you are historically "on-top" of your pool and its chemistry is certainly an advantage to completing a SLAM quicker after catching a possible algae bloom in its early stages. Interesting though that you boosted you FC to 11 and you saw some water issues upon your return. But if you typically lose 3-4 ppm of FC each day, and started at 11 before your trip, I suppose it's possible for your FC to have dropped dangerously low between 24-48 hours, ending-up to about 3-4 ppm. You certainly had rock-solid numbers last night and this morning, so I would watch to make sure your filter continues to catch any residue and let us know if you see anything else unusual. Maybe some others will chime-in with a thought or two as well. Have a good day.

 

[chem geek]

It all depends on how much algae there is. It sounds like there was very little, being isolated to just the floor to wall edge and being spotty. So that wouldn't be expected to show up with much chlorine demand. Most likely, that area is one of poor circulation and that would also reduce the amount of chlorine loss. Your pump being on low may not be circulating the water near the bottom well enough. Usually a pool sweep helps to circulate the water some at the bottom and sides of the pool. Do you have a pool sweep?

The only thing I can suggest you do the next time you will be going away is to not only elevate the chlorine level, but also brush the pool after you've added the chlorine and had the pump on high for at least 30 minutes. That should distribute the chlorine more evenly to prevent algae growth.

 

[dprosper75]

Thanks for the info guys!! I got home and there was hardly any chlorine loss at all but the pool is still milky looking which I'm sure is the
dead algae. I did backwash and filter and make sure it is on high and will keep it there till it becomes clear again.

I do generally run my 2 speed pump on low most of the time and generally kick it on high when a bunch of people are over.

I do feel that it could be a circulation issue as it is a pretty big above ground pool with only one jet. Which would lead me to the question....what is the best position of the output jet? Right now it is (standing behind the jet) down a bit and to the right. What
is optimal? I do keep a solar cover on the pool almost every day. Should it point more to the bottom and right to get a rotation effect going on??

ChemGeek...what do you mean a pool sweep? Like a polaris or something like that which automatically cleans the pool?

 

[chem geek]

Yes, I meant an automatic pool cleaner like a Polaris or other brand. Anything to move around the bottom of the pool to help circulate the water there.

Well you describe a situation that most certainly qualifies for poor circulation with a 17,000 gallon pool with only one return. You can certainly try pointing more downward to the side to try and get more of a rotational circulation, though that may make your skimming action worse. However, with the solar cover, you aren't getting any skimming anyway. You should probably set your pump to go on high speed for a short time a few times during the day. Even one hour twice a day or 30 minutes four times a day would likely help out a lot in your situation, but you'll just have to experiment with what works best and report back so others can learn as well.