a little green algae

[pool-liner4me]

These were my numbers this morning:
FC - 4.0 (added 43 oz. chlorine to bring it up to 5.5)
CC - 0.0
pH - 7.4 (just dropped to 7.4 from 7.6 a few days ago)
TA - 70
CH - 130 (haven't tested this for awhile)
CYA - 35

We just got our new liner last August. I have kept the pool vacuumed and clear of debris throughout the winter and the chlorine levels at around 5.0-6.0. It has not once dropped below 3.0 and I have had a crystal clear pool all winter long. We've had a lot of cloudy days this winter, but are finally getting a little sun and I noticed this morning a small amount of green algae on the shady side of the pool in a couple of places, which I brushed off this morning. Over the winter both the pH and the TA have been slowly decreasing, but I have yet to add anything to increase or decrease either one. We are running our pump 4 hours per day. I usually brush the sides of the pool once a week and throw the Kreepy Krauley in for 8 hours every other weekend. I thought my numbers were within the appropriate range for my 18,100 gallon vinyl liner in-ground pool. Is there something that I should be doing differently to prevent the algae from forming, especially as the days become sunnier? During the winter, the 10% bleach I got from Lowe's was dated Aug 2018. I am still using it and store it in my shed. Do you think it has lost its potency and I should be using more to compensate, or would that show up in the FC numbers? Thanks in advance for your help and advice.

 

[mknauss]

The best thing to do is SLAM the pool to eradicate the algae and then maintain the FC based on the FC/CYA ratio. Use CYA of 40 (round up).

I know your current FC is good according to the FC/CYA ratio, but for whatever reason you must have had a time were that area did not get well circulated, etc.

The best way to check your liquid chlorine is to add some based on a certain FC using PoolMath. Then circulate for 30 minutes and test again to see if you got the FC rise expected.

 

[jmikeb]

These were my numbers this morning:
FC - 4.0 (added 43 oz. chlorine to bring it up to 5.5)
CC - 0.0
pH - 7.4 (just dropped to 7.4 from 7.6 a few days ago)
TA - 70
CH - 130 (haven't tested this for awhile)
CYA - 35

We just got our new liner last August. I have kept the pool vacuumed and clear of debris throughout the winter and the chlorine levels at around 5.0-6.0. It has not once dropped below 3.0 and I have had a crystal clear pool all winter long. We've had a lot of cloudy days this winter, but are finally getting a little sun and I noticed this morning a small amount of green algae on the shady side of the pool in a couple of places, which I brushed off this morning. Over the winter both the pH and the TA have been slowly decreasing, but I have yet to add anything to increase or decrease either one. We are running our pump 4 hours per day. I usually brush the sides of the pool once a week and throw the Kreepy Krauley in for 8 hours every other weekend. I thought my numbers were within the appropriate range for my 18,100 gallon vinyl liner in-ground pool. Is there something that I should be doing differently to prevent the algae from forming, especially as the days become sunnier? During the winter, the 10% bleach I got from Lowe's was dated Aug 2018. I am still using it and store it in my shed. Do you think it has lost its potency and I should be using more to compensate, or would that show up in the FC numbers? Thanks in advance for your help and advice.

to check your chlorine, use pool math an increase your fc to number that you like. then recheck it in 30 mins or so. if it tested at the level you expected, your fine.
btw, my chlorine from july 2018 was almost completely dead

 

[pool-liner4me]

Marty, thank you for your advice. I have been using Pool Math to calculate daily how much chlorine to add and at CYA of 35 I was using a FC level of 5.5. It's been about 2 hours since I added the chlorine, but I just went out and retested my water and my morning's addition of chlorine only got to 5.0, not 5.5 as expected. So would that indicate my chlorine is weak? I will round up my CYA to 40 and use a FC level of 6.0 in the future. I usually add my chlorine at the deep end and sometimes just broadcast the liquid across my pool. I don't have muriatic acid so will have to get some to bring my pH down to 7.2 before slamming, so will try to get out today to get that and start slamming tomorrow. Haven't ever had to do that yet.

 

[pool-liner4me]

jmikeb, thank you also. I suspect my chlorine isn't very good anymore. I just picked up some new chlorine from HD so will try using that tomorrow.

By the way, I forgot to mention that my water temperature is 52 degrees so my CSI is -0.7, but I expect it to come back into range once the water heats up.

 

[Texas Splash]

my water temperature is 52 degrees so my CSI is -0.7,

Plus, you have a vinyl pool with no heater, so CSI isn't a huge issue for you on most days. But do your best to maintain that FC SLAM level. You might search some threads here for chlorine sources in CA. I believe others found some decent deals other than just the big box stores. Good luck with your SLAM!

 

[pool-liner4me]

Hello, me again. Thank you all for your advice prior to my first ever SLAM. So due to family emergency I was unable to actually start the SLAM until this past Friday (I have to do SLAM on weekends when I can run filter full-time as we are on a metered electrical use on weekdays between 3:00-8:00). I still only saw a little bit of green algae, so the problem did not appear to have worsened. The numbers before SLAM were:
FC=5.0
CC=0
pH=7.6
TA=70
CYA=40
CH=170
Temp=58

I began Friday morning with filter running by adding muriatic acid (36 oz.) until my pH reached 7.3. Had to turn filter off at 3:00 until 8:00 PM and by that time was FC was 4.0. I wanted to add my first chlorine to work overnight so at 8:00 PM Friday evening I turned the filter back on and added 278 oz. (2 gal. 3 cups) 10% chlorine to bring FC to SLAM level of 16 using pool math, but didn't test again until Saturday morning at 8:00 when FC was 17.5 so I didn't add any chlorine at that time (I think I still had my CYA set at 35 instead of 40 and that's how I got the wrong initial amount of chlorine to add; that has since been corrected). I brushed the pool and then retested at 11:00 AM, FC=11.5 & added 104 oz (3 qts. 1 cup) chlorine; tested again at 2:30 PM, FC=10.0 and added 139 oz. (1 gal. 1 cup) chlorine. Around 5:00 I put the Kreepy Krauley in and began vacuuming the pool; tested again at 8:00 after sunset, FC=12.0 and added 93 oz. (3 qts.) chlorine, waited 2 hours and checked FC which was 14.5. Didn't add any chlorine as I wanted to see if I passed the OCLT test.

So it's now Sunday morning. I passed the OCLT test with flying colors, FC this morning was 14.5; and CC is 0. Water is clear, no sign of algae. Although I am thinking I may be done with SLAM even though its only been 24 hours, I am not sure as a few days prior to SLAM I had passed an OCLT test and had CC of 0 as well, but was seeing a small patch of algae. Should I continue SLAM through today to be sure while I can still run filter 24/7? Or am I well and truly done with it? I am a Senior trying to do this on my own as my husband is disabled, so I am ever so grateful that I found your website that makes it so easy to maintain the pool. You guys are great!

 

[Texas Splash]

A 3-say SLAM is very optimistic and quite fast, especially if you couldn't run the pump 24/7 for optimal filtration. If your water wasn't too bad, I suppose it's possible, but it's best to be sure. If you see NO cloudiness or algae, and you passed the OCLT w/ no CC readings either, you should be done. You're in the best position to see, so I'm afraid it's your call. Always best to make sure so you don't lose all the work and progress you did the past few days.

 

[pool-liner4me]

Thank you. The filter has been running continuously since 8:00 Friday night. I think I'll continue the SLAM through today, just to be sure, do another OCLT tonight and if all looks good will let FC drift down to about 6 during the next couple of days. One more question: Once FC gets to 6 should I bring my pH back up to around 7.6 or just leave it at 7.3? Although my numbers for a vinyl pool all are within range, I saw somewhere on this website (pool school or forum) that one of the biggest issues with a vinyl pool was to have the pH too low. I was a little confused as to whether it is better to have it higher with a CYA of 40 so that chlorine is not eaten up as quickly, or to keep it lower. Can you clarify that for me please?

 

[Texas Splash]

I think you're fine to leave the pH and others where they are for now. I suspect your pH will rise fairly soon on its own after the SLAM. As for the CYA, 40 may work for now if the sun isn't too intense. It should provide adequate protection for the chlorine. But as summer approaches, if you find the FC dropping too quickly (more than 4 ppm in 24hrs), with no hints of algae, then the FC may need a slightly higher CYA. Just something to watch as the heat picks-up.

 

[pool-liner4me]

Oh, thank you, Pat. That helps a lot! Was very fearful of my CYA getting over 50 and having to drain my pool and run the risk of messing up the vinyl liner, so was keeping it lower. But you have explained the correlation between CYA, sunlight, and FC, as long as my CYA does not exceed 50 (as someone in an earlier post of mine cautioned). Will keep an eye on it. Thanks again.