It just won't go away

[buddyw62]

Hi all. My first post here, although I've been around since July 2020 reading. Lot's of good info on this forum, and I thank you for all of it. It's been a big help!

We have an above ground 24' pool, 7 years old, purchased in 2016 (our 2nd 24' above ground).

So the last 2 years we've fought with algae. Brown patches on the bottom and greenish around the bottom edges. You'd think it would go away, and it seemed to after brushing and slamming it, but it always came back. Backwash was also milky. Seemed I spent a fortune in bleach and chemicals - and I did.

So this year, early on we noticed a leak. Not sure where it was coming from but leaking nonetheless. So, we replaced the liner. With fresh water, algecicde, and 2 gallons of bleach we covered it in February (solid cover).

First weekend of May we pulled the cover off. Water was crystal clear. So, having a sand filter we replaced the sand, rinsed, added bleach water in the filter (no sand), and let it set for several hours. Drained, filled it with 150 pounds of filter sand. Replaced the hoses, new 1 HP pump, and new steps. Last steps had 40 pounds of sand in them for weight, which I suspected had algae in them as well, so we bought new ones - no sand this time, but 2 - 40 pound weights to weigh them down. Basically everything except the pool frame is new. Tested the water and of course everything was off. Started with algaecide, 2 pounds shock (Turbo Shock by Pool Life, 78% calcium hypochlorite - wife wanted to switch back from bleach), and began getting the CYA up gradually. All is well for the time being.

Until now.

Yesterday I back-washed after vacuuming, and the backwash was milky, very milky. Beginning to see some brown spots in the bottom also. Not sure what I'm doing wrong. Added 2 pounds shock yesterday evening.

Here's the test from today (Taylor K2006C):
Water Temp - 76 F
Hardness - 160
Ph - 7.4
Alkalinity - 90
Total chlorine - 5 ppm
Free chlorine - 3 ppm
CYA - 35

Any help is appreciated. About at my wits end. And thanks in advance.

Buddy

 

[HermanTX]

Welcome to TFP.
It is really important to follow the recommended TARGET levels. For CYA of 40 (always round up), the target is 5-7ppm for FC.
You are toying with the minimum which is why there is algae.
It is best to use liquid chlorine. The “shock” you are using is not helping and is only a temporary increase. Use LC daily and get your FC to the high side.
You need to follow a SLAM first as you need to get rid of the existing algae.
SLAM Process

 

[newdude]

Herman has you well covered in the short term, and here's what you'll do going forward.

Everyday, UV from the sun burns off chlorine. Minimum is obviously the danger zone where you'll allow problems to start. So minimum is your absolute lowest FC level. For 40CYA, it's 3ppm FC.

Now. Daily UV loss changes throughout the season. There are occasional weeks that are unusually warm/cool, but for the most part, think of a bell curve. You may lose 2 ppm a day in April/May, 3 or 4 ppm a day in June/July/Aug, then 2ppm again in Sept as the season winds down.

The 7 ppm high target is fine in May, but leaves no wiggle room in July. You need to adapt as the season changes so that when you dose, you never get near minimum at the next test/dose time. It's the simplest equation ever:

Minimum (for your CYA) +
Recent daily loss +
1 or 2 ppm wiggle room (for storms, extra hot day, lots of swimming after dinner, etc).

Say you're losing 4ppm a day in August and you find the FC is a 6. While 6 is 'in range', 6-4=2 and you'll be below minimum by tomorrow. This is how you fight algae all summer thinking the 6 was fine. Or dosing to 6 because it's 'in range' of 5-7. But 6 worked GREAT in April, when you lost 1 or 2 ppm a day, so it fools you into thinking it's still fine in July. It's a moving target and you need to move with it, to be trouble free.

So when you find a 6 and have been losing 4 per day, dose to an 8 or 9 to have 4 or 5 left tomorrow, with insurance FC for whatever arises in the meantime.

Follow

Minimum+
Recent loss+
Wiggle room

And we'll never discuss your algae again.

 

[buddyw62]

Thanks HermanTX and Newdude

I appreciate the feedback! Everything you said makes perfect sense. I will be switching back to bleach - against the wife's initial wishes but she gets it now kindof...

SLAM'ing this evening with LC and will maintain after that at the higher level and follow your guidelines. I'll post again with the results but I suspect this should cure it.

Once again, THANK YOU!

Buddy

 

[newdude]

Remember it's a 'process'. Follow said process to a T and you'll be posting to How Clear is TFP Clear? in no time.

 

[buddyw62]

Update since I last posted. I followed your instructions, using LC SLAM'd it first, then kept the FC level around 7 ppm. Losing about 2-3 ppm / day now although the weather is finally getting hotter here so I'm sure the daily loss will go up. I'll monitor and adjust. First backwash was slightly milky, next ones normal. No algae. Wife is happy.

 

[reggiehammond]

Just to be clear: CalHypo "shock" and liquid chlorine are the same thing. They're both chlorine - one just comes with a bunch of calcium that builds up over time, and if not careful, can lead to scaling. Liquid chlorine is just like "shock" except it doesn't carry with it any problem chemicals like calcium or CYA.