first SLAM and it isn't working

[AJWolverine]

pre SLAM numbers from Friday:
CYA 22
PH 7.2
TA 160
FC 3
CC .5

History:
I've been struggling with the alkalinity all summer. It was 230 at one point! Adding muriatic acid to lower the alkalinity made the ph plummet then bringing the ph back up raised the alkalinity. We aerated for several weeks to get the alkalinity down to 160.

I know the CYA is too low. I read that you should test a week after adding and also that once it's too high the only way to lower it is to drain the pool so I thought I was being cautious about adding just a cup at a time each week. I've added about 5lbs to a 7,000 gallon pool over the last two months and it has hardly budged per my Taylor test kit. I'm baffled.

So that brings us to today's algae bloom...
Despite the issues above the pool's been beautifully crystal clear all summer. I've been testing every morning and adding enough bleach to keep it around 4-5. Friday night I noticed it developing a yellow tint with brownish dust on the bottom as I vacuumed. I tested to get the results above. I brought the FC up to 15 with bleach, but by Saturday morning it was light green and cloudy. I've brushed twice a day. The FC numbers aren't falling dramatically like I would expected based on what I've read. It's still 15 this morning.

Any thoughts and advise from experienced pool owners would be appreciated.

 

[zea3]

When was the last time you tested the CYA? Are you reading the test in full sun, with the sun at your back and the viewing tube at waist level? Don't stare at the dot, glance in and glance away. Did you broadcast CYA into the pool or did you put it in a sock hanging in front of a return?

 

[AJWolverine]

When you say return, you mean where the water returns into the pool from the filter, right? That's where I hung the CYA in a sock. Although I ran out of the Taylor kit solution for CYA a couple weeks ago, daily strip tests back up the low CYA level. (I've still been testing FC, ph and alkalinity twice a week with the Taylor kit and those results correlate to the daily strip tests). Friday night when the water first started getting discolored I had a local pool store test also, which matched my results closely. I've added a cup of CYA since they tested it at 22. I know store tests can be unreliable. This one was done within 15 minutes of the sample being taken and correlates to my other tests so I'm confident it really is low.

 

[zea3]

Yes, the return is where water returns to the pool. Unless you have replaced a lot of water, the CYA should be around 86 based on adding 5 lbs to a 7000 gallon pool. What brand of CYA did you use?

The CYA test is the most subjective test to read. The pool store cannot conduct the test correctly as they test it indoors under fluorescent lights. Test strips will not read CYA anywhere near accurately. Its pretty much pointless to take a CYA reading from a test strip. Have you ordered more reagent for the CYA test?

 

[tim5055]

Remember, a SLAM Process is a process, not a one or two time addition of chlorine that instantly makes everything go away. As an example, earlier this year after a trip I noticed my pool was not quite as "sparkling" as usual. Not cloudy, but a little "dull" looking. I tested and discovered that my FC was "0" because my Stenner Pump failed while I was away. An Overnight Chlorine Loss Test proved something was growing, even though I had no visible algae.

I started a SLAM Process and it took the better part of a week to pass the SLAM Process.

At this point you have visible algae so your SLAM Process will be longer and more involved. You must test and adjust the FC back to shock level multiple times a day, remembering to brush at least once a day. I could be reading this wrong, but it seems you have brought it to shock level a couple of times this weekend. Yo need to maintain (that is the M in SLAM Process) it at shock level as much as possible for as long as it takes to eradicate the algae.

You need to order more reagents for your kit, stop using strips and stop going to the pool store.

 

[AJWolverine]

I have ordered more reagent. I understand that testing now, with cloudy water, won't yield valid results, correct?

- - - Updated - - -

The brand was SunShield.

 

[mknauss]

I have ordered more reagent. I understand that testing now, with cloudy water, won't yield valid results, correct?

Unless your water is extremely murky, the CYA test will work. Get a small glass of the pool water, how cloudy is that?

Take care.

 

[zea3]

I have not heard of any problems with the sunshield brand of CYA. From the way your pool is responding, I would say the CYA is actually very high, and you have not added enough chlorine to kill the algae. Until the reagent comes in add a large jug of bleach per day to keep things from getting worse. Test the CYA when you can and report the result. You will probably need to drain at least 1/2 the pool and refill to get CYA at a reasonable level to slam the pool.

 

[AJWolverine]

I borrowed reagent to test CYA and you were right about the level being way too high. I drained water, added more bleach and now it's cloudy but no more green so it's definitely a huge improvement. I'll run the filter for a while to hopefully clear it up soon, before refilling the rest of the way.

Thank you for your help.

 

[mknauss]

You need to SLAM Process.

This is a chemistry problem, not a filtering problem.

 

[DeanP66]

The pool store strikes again!!!