Another high CYA pool user

[jb]

Had my pool for 17 years. Plastered & remodeled when moved in, then again 2 years ago. I always thought I was pretty good at chemicals - not so much. I have been using tablets and granular this whole time. Before the last remodel (2 years ago) it was getting hard to keep the algae at bay. But with the new plaster and 'new' water, year 1 was easy peasy. Had an automatic chlorinator installed as part of remodel #2. Would just fill it once a week and pool sparkled all summer. Most of year 2 was pretty much the same. Now starting third year and annoying algae popping up. I brush it, turn chrorinator up higher and higher ad granular (which I never had to do year 1 ) it goes for a few days then it is back. Pool store said I needed to ad phosfree to keep the phosphates at bay. I have been doing that, but the algae persists.

So what do I do? I come to TFP of course. Been here a few other times for problems and it has always helped. Well, I spent only about 30 minutes reading and figured out I am doing it ALL wrong lol! One of the pool chemistry articles said tablets work fine until one day they don't and algae pops up and the pool owner doesn't know why - me!

So tested my CYA and that black dot disappeared fast! I look at the mark and its 100 - ugghhh. So now at least I know why my chlorine isn't as effective anymore. I am going to buy some liquid chlorine later today on my way home and start adding that immediately and forever going forward. I will monitor my pool the next few days, read more on here and decide if a partial water exchange is in order or not. My pool does sparkle and look clear but has the algae on the walls - in places - not everywhere. Any advice welcome and thank you to all the great pool experts and enthusiasts on here. Is this a great place or what?

I also tested out my
FC 5ppm
TC 3ppm
TC-FC = -2ppm ?!
PH 7.2
CYA 100

 

[mknauss]

100 is the limit of the CYA test, so you have to do a diluted test. Mix 50% pool water with 50% tap water. Use this mixed sample as your test water. Multiply the result by 2 for your CYA level.

If you have visible algae, you need to follow the SLAM Process

How are you testing your pool water chemistry?

 

[jb]

I have the Taylor K2005 test kit

I just redid the CYA test per your suggestion with 1/2 pool water and 1/2 tap water. I got 80. So 160

 

[mknauss]

So you need to drain at least 75% of your water volume and replace with fresh.

I would also suggest you purchase a FAS-DPD test kit. They are available from TFTestkits.net.

 

[jb]

Thank you for that advice. I will pick up a FAS-DPD test kit.

 

[jb]

Test kit ordered. Been draining for about 6 hours. Still aways to go. Hopefully around midnight I can turn off the drain and on the hose or else I'll be setting the alarm for the wee hours of the morning...

 

[jb]

Drained until midnight. Put both hoses on wide open on the way back up. Local pool store has 4gal 12.5% liquid cl for $20 so going to pick that up to have ready.

 

[jb]

Well back up and running. Took about 12 hours to drain , 18 to fill. Measured CYA when it was ‘close’ to full maybe 12” low and got 80 so was a little dissapointed and thought maybe I hadnt drained enough. But maybe the water wasnt circulated enough either. Filled rest of the way. Used math app to determine to add 4 gals of 12.5 percent cl. Ran pool over night and this morning got 45 CYA whoohoo. FC 4ppm ph 7.4 The small amount of algae I had on the walls is almost gone. Ill brush it anyway. Any more advice at this point?

 

[BadDogPSD]

Round your CYA up to 50 and add chlorine accordingly. Since you had algae before your drain & refill, you might want to raise your chlorine to SLAM levels (20ppm) to keep the algae away. I'd add 3.5 more gallons of chlorine.

 

[jb]

I'm tempted as I have another 4 gal handy - I bought 8. If I do that how long until we can swim?

 

[JJ_Tex]

Make sure you are understanding the SLAM process. It is not a simple dump in some chlorine, its raising your FC to a certain level (20 in your case with a CYA of 50) and keeping it there until all of the algae is dead. And by dead, we mean not just the visible algae on the walls but also the algae that is not visible in the water. Your pool water looks pretty good, so I cant imagine it will take more than a few days of a SLAM and then you can start swimming again.

SLAM - Shock Level and Maintain

We’ve all had to deal with a green pool. Clear algae from your pool with a SLAM! Read here to use shock level and maintain to clear your pool.

www.troublefreepool.com

 

[jb]

Ok. Thanks for that I think Ill wait. Have a pool party coming up in a few days and dont want the stress of being done before then. Once that is over Ill slam it, take my time and do it right.

 

[jb]

Plus my FAS-DPD may arrive by then

 

[mknauss]

If I do that how long until we can swim?

You can safely swim in a pool as long as the FC is above the minimum and at or below SLAM level based on your CYA. You must also be able to see the bottom of the pool in the deep end of the pool.

 

[jb]

I received my FAS-DPD test kit yesterday and obtained the following results this morning;

FAS-DPD;
FC 6ppm
CC 0ppm
TC 6ppm

Then with my Taylor kit;
FC 2ppm
CC 0ppm
TC 2ppm
ph 7.8
CYA 40

Any idea why so much discrepancy between the Taylor and FAS-DPD results?

Pool looks great, just the tiniest amount of algae has surfaced in one corner of the spa and disappears with a light brushing. Still planning to SLAM the pool next week.

Edited to ad I did both tests twice, carefully, and got the same results both times.

 

[mknauss]

What FC test are you calling the 'Taylor' kit?

 

[jb]

I mentioned earlier, but it is the K2005 kit
FC test; basically
5 drops reagent 001
5 drops reagent 002

 

[mknauss]

The FAS-DPD test is more accurate than the test in the K2005.

 

[jb]

Slam in progress! Pool ap suggested 6 gals to bring my FC up to 18. Tested it an hour later and was at 22. Not too bad. Figured it would float down soon enough. 4 hours later was about to take an afternoon siesta and thought, don't need to check it as its probably close to 18 now right? Wrong! Decided to go check it and it had dropped to 13! Wow the sun brings it down fast. Got it back up again. (pre siesta) Pool looks a little hazy after the 6 gals went in but returned to clear a few hours later. Been brushing. There appears nothing to vacuum. Pool looks immaculate. Should I vacuum anyway? Found a tiny bit of black algae. Should I do anything special there?

 

[jb]

My overnight FC loss was from 19ppm top 16ppm . I didn't get to check it before the sun hit the pool. Maybe the sun hit it for 30 mins, partially. What would you guys suggest? Passed the other portions of the test including CC 0ppm, water clear.