UPDATED: New numbers; SLAM questions

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Pool-in-the-Hills

Member
Apr 6, 2021
24
Litchfield County, Connecticut
Pool Size
15000
Surface
Plaster
Chlorine
Liquid Chlorine
This is a long post because I am opening my pool on my own for the first time this year. TFP and the test kit have been invaluable to this process - Pool Math, the forum, all of the wonderful advice has been so encouraging. But, this mustard algae is giving me a run for my money. Please advise.

(Skip to day 19 if you would like to see the mustard algae numbers only.)

April
1 Pool cover removed, water is light green, can see to the bottom of the shallow end (3')
4 Cleaned sand in my filter (thank you for the directions - easy to follow and made a world of difference!)
5 Hooked up equipment; pump runs 24/7
6 Received test kit from TFP! Results:
CYA=60
pH=7.5
TA=210
CH=325
FC=1
CC=0
TC=1

My goal in SLAM is FC=24. I did not yet think I had an algae issue. Oy.

Each day I tested, brushed the pool sides and stairs at least twice, and the robot worked at least several hours.

7 9:15a 1 gal liquid chlorine 10%
12:15p 1 gal LC 10%
4:15 FC=5; 1 gal LC 10%
8 10a backwashed; FC=12; 1 gal LC 10%
1p 1 gal LC 10%
4p FC=20; 1 gal LC 10%
9 10a backwashed; FC=21; 1 gal LC 10%
***A few issues caused us to neglect the SLAM for a few days, but it was totally clear during this time.***
14 10a backwashed; 2 gal LC 10% (I didn't record the FC, but certainly took the test before I added chlorine)
3p 2 gal LC 10%
15 9:30a backwashed; FC=22; 1/2 gal LC 10%
16 10a FC=18; 1/2 gal LC 10%
2:40p 1 gal LC 10%
4:45p FC=22; 1 gal LC 10%
17 9a 1 gal LC 10%
12:40p FC=30
4:45p FC=26; 1//4-1/3 gal LC 10%
18 9a backwashed; 2/3-3/4 gal LC 10%
1p FC=31
4p 1 gal LC 10%
19 Checked in on TFP and thought, oh gosh, I think that sand-like substance I have been pulling out of the robot filter is mustard algae. :( New goal is FC=35. Pool is brushed WELL, sides (including the tiles) and as much of the floor as I can get (most of 9' deep end, but probably not very well), 3-4 times a day, which means the pool is now cloudy (but we can still see the bottom of the deep end). Robot is still picking up "sand", but not much (I will post photos of this and a video of the cloud from brushing). I am getting a skimmer sock.
9a FC=24.5; 1/2 gal LC 10%
1p FC=22; 3/4 gal LC 10%
5p FC=27.5; 1/2 gal LC 10%
20 9a FC=29.5; 1/2 gal LC 10%
11:15a backwashed; FC=31.5; 3/4-1 gal LC 10%
1:45p FC=31; 1 gal LC 10%
3:45p ? gal LC 10%
4:45p 1/2 gal LC 10%
21 (today!) 9a FC=27; 1 gal LC 10%
12p FC=27; 1 gal LC 10%
3-4p HUGE rainstorm - only mentioning because I'm wondering if this made a difference...
4:30p FC=40.5; took photos and video (I will post below)

Is this mustard algae? We have had huge algae issues (according to our former pool opener/closer), but nothing was ever done other than dumping 15 gallons of LC into the pool at opening, advising us to use an algaecide when it gets green, and calling it a day!! If so, am I doing everything I should be doing? What else?

Thank you!
 
Re-read the mustard algae instructions. SLAM as usual, at the regular SLAM level. Once that is done (passing all three criteria), then you raise to the MA level on the chart and hold it there for 24 hours before exiting SLAM. Your excessive FC levels for long durations are risking damage to your pool and equipment.

You have a sand filter, recently deep cleaned. It's possible that one of the laterals was damaged and the sand-like substance is actually sand. It's also quite early in the season for mustard algae - mustard likes it hot. It usually is found on the shade-side walls.

Rain doesn't really do anything to a pool unless it's a tropical storm or hurricane that washes a lot of debris into the pool.

Continue your SLAM at the normal SLAM target. Keep doing what you're doing, testing and adding several times a day, running the robot and brushing what the robot misses, until the water is crystal clear.
 
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I was worried about all of the issues you mentioned; however, our pool was clear until I started brushing more (and more aggressively). Our water is never over 50-degrees, so your reasoning makes sense.

So, just to make sure I understand - I go back to my SLAM goal of FC=24, meet the three criteria for SLAM - which includes no "dust" coming off of the wall or the floor, right? And then, if there is still sand in the robot but no "dust" coming off of the walls and floor, I have a probable broken lateral.
 
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If the sand is gritty when rubbed between your fingers then it's just that: sand. From the looks of it I would definitely consider a broken lateral as the prime suspect, this is especially true since you just opened the pool and freeze damage is one of the most common ways a lateral can be damaged.
 
It's sand. Ugh. Can I wait until the end of the season to deal with the lateral? I would love to just let my kids swim, if it's not a critical problem. There is very little sand that has escaped.

A couple of other concerns:
FC=23.5 this morning, down from 40.5 at 4:30 pm yesterday. I brushed - lots of cloudy algae (THIS is algae, yes?), but definitely not clouding up the entire pool. We added just a smidge of LC 10% in front of the jet (we usually add it to the return - does it matter?)

I checked the date on the LC, as I read on here yesterday I should do. The date seems to be 20091015. Am I misreading something? The FC goes up every time I add it; doesn't that mean it's active? Could the date be somewhere else? My local hardware store received a delivery of the LC just before I bought it, which made me think it was fresh. Can someone help me with this? thank you.
 
If you aren't losing much sand I think it can wait. But it doesn't take much time to replace the laterals. I did it last year, a few months after back surgery, in an afternoon. Scoop out the old sand, remove the old lateral assembly, place new one, *cover the center tube*, refill with sand, done.

Chlorine, like most chemicals, should be poured slowly in front of the return jet with pump running. This mixes it as quickly as possible. You don't want to pour chemicals into your skimmer, as this sends concentrated chems through the equipment, which is hard on it.

I wonder if your date code of 20091015 means year 20, month 09, day 10, hour or manufacturing line 15. Old chlorine still will increase your FC, just not as much as fresh. Add, then test again in 30 minutes to see if you reached your target. If not, you'll need to adjust how.much you're adding in order to compensate.
 
I am going to wait and see with the sand; I will change the laterals if it looks like the sand is increasing at all.

Your numbers make sense. The chlorine is pretty strong, I think, as my FC went from 23 at 9 am, to 27.5 at 12:30 pm, after I added maybe 1/10th of a gallon of LC to the pool at 9 am. It has slowly gone down today - 26 at 2:30 pm, 24.5 at 5:30 pm. It is freezing here (literally), so I might wait until tomorrow do test and add again. The algae is still there, but not as much. Thanks to TFP, we are getting there!
 
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I listed these results originally in the algae forum, but discovered that I had a sand leak, not algae. I *think* I have been uselessly torturing my poor pool thinking that the yellow clouds were algae; now, I think they are pollen and sand. SLAM has been going on for 25 days (with only a brief break). The daily results and my actions follow. This is my first time opening my pool and, while I try to follow TFP, I have clearly misunderstood some things along the way. Questions are at the bottom.

April
1 Pool cover removed, water is light green, can see to the bottom of the shallow end (3')
4 Cleaned sand in my filter (thank you for the directions - easy to follow and made a world of difference!)
5 Hooked up equipment; pump runs 24/7
6 Received test kit from TFP! Results:
CYA=60
pH=7.5
TA=210
CH=325
FC=1
CC=0
TC=1

My goal in SLAM is FC=24.

Each day I tested 3-4 times, brushed the pool sides and stairs at least twice, and the robot worked at least several hours.

7 9:15a 1 gal liquid chlorine 10%
12:15p 1 gal LC 10%
4:15 FC=5; 1 gal LC 10%
8 10a backwashed; FC=12; 1 gal LC 10%
1p 1 gal LC 10%
4p FC=20; 1 gal LC 10%
9 10a backwashed; FC=21; 1 gal LC 10%
***A few issues caused us to neglect the SLAM for a few days, but it was totally clear during this time.***
14 10a backwashed; 2 gal LC 10% (I didn't record the FC, but certainly took the test before I added chlorine)
3p 2 gal LC 10%
15 9:30a backwashed; FC=22; 1/2 gal LC 10%
16 10a FC=18; 1/2 gal LC 10%
2:40p 1 gal LC 10%
4:45p FC=22; 1 gal LC 10%
17 9a 1 gal LC 10%
12:40p FC=30
4:45p FC=26; 1//4-1/3 gal LC 10%
18 9a backwashed; 2/3-3/4 gal LC 10%
1p FC=31
4p 1 gal LC 10%
19 Checked in on TFP and thought, oh gosh, I think that sand-like substance I have been pulling out of the robot filter is mustard algae. :( New goal is FC=35. Pool is brushed WELL, sides (including the tiles) and as much of the floor as I can get (most of 9' deep end, but probably not very well), 3-4 times a day, which means the pool is now cloudy (but we can still see the bottom of the deep end). Robot is still picking up "sand", but not much. **I was wrong about the algae, I am pretty positive. It was definitely sand.
9a FC=24.5; 1/2 gal LC 10%
1p FC=22; 3/4 gal LC 10%
5p FC=27.5; 1/2 gal LC 10%
20 9a FC=29.5; 1/2 gal LC 10%
11:15a backwashed; FC=31.5; 3/4-1 gal LC 10%
1:45p FC=31; 1 gal LC 10%
3:45p ? gal LC 10%
4:45p 1/2 gal LC 10%
21 9a FC=27; 1 gal LC 10%
12p FC=27; 1 gal LC 10%
4:30p FC=40.5
***TFP helped me realize that the sand in my filter was actually sand. FC goal is 24.
22 9a FC=23.5; 1/10 gal LC 10%
12:30p FC=27.5; backwashed (very yellow)
2:30p FC=26
5:30p FC=24.5
23 9:45a FC=22; 1/10 gal LC 10%
4:30p FC=21; 1/4 gal LC 10%
24 *forgot to write it down (!!!) but I know FC hovered between 21 and 18
25 1:30p FC=18; 1/2 gal LC 10%
4:30p Revisited TFP forum because I felt like this was just too long for SLAM. Advice to someone else was to do a complete water test, so I did this. Results:
CYA=50
pH=8.2
TA=200-210
CH=275
FC=19.5
CC=0
TC=19.5

Questions:
1. What do I address first? Obviously (I think?), no more adding chlorine. Let it come down to non-SLAM levels. But, pH is terribly high. Take care of that first?
2. Have I ruined my pool equipment?! How can I know?
3. Is it possible I do still have algae? Even though the FC levels were so high?
4. When can I turn the heater on and swim?

THANK YOU!
 

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Pool-in-the-Hills said:
Questions:
1. What do I address first? Obviously (I think?), no more adding chlorine. Let it come down to non-SLAM levels. But, pH is terribly high. Take care of that first?
2. Have I ruined my pool equipment?! How can I know?
3. Is it possible I do still have algae? Even though the FC levels were so high?
4. When can I turn the heater on and swim?

THANK YOU!
Click to expand...
1. Let the FC drop, the more sun it gets and time, it will go down. Using PoolMath, add muriatic acid to take your pH down to 7.8. Brush where you add the acid just to prevent any staining.
Retest to determine if you hit that 7.8 pH. If not, repeat. You may actually be above 8.2.... so it may take a few doses. Go slow. Once pH is down to 7.8, try to take it down to 7.6...repeat, and then 7.2. Each time you add acid it will lower the TA a bit.
www.troublefreepool.com

Lower Total Alkalinity

A lower Total Alkalinity level can help a pool owner stabalize their pH increase. We'll explain how to lower TA with a little help from muriatic acid.
www.troublefreepool.com www.troublefreepool.com

2. If you broke it, you'll know. If all is well you just know you have the cleanest pool in town.

3. You can have algae anytime your FC is below the level which corresponds to your CYA. FC/CYA Levels

4. Its safe to swim any time the FC is less than your SLAM level, based on your CYA. As for the heater, it should be fine. You never want too low pH as that can chew thru the heater coils. Always keep your pH at least 7.2.

YOU'RE WELCOME!

Maddie :flower:
 
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