Closing soon…but algae showed up

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M

mrm1682

Bronze Supporter
Apr 25, 2021
173
NJ
Pool Size
13000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-9)
I’m scheduled to have my pool closed in 2 weeks but not sure how aggressive to deal with this algae issue now. I had this dirt like yellowish stuff that I presume is mustard algae. Hadn’t gotten worse but not going away. Recently we’ve had constant rain last 4-5 days here and I’ve had to drain water out 3 times since the water level was above the top of the skimmers. Yesterday during a quick break in rain I was brushing the pool and there’s clearly some more algae on the bottom in different patches. The water itself is clear though. I know all my numbers are going to be off after all this rain so I plan on testing today once rain finally passes but how aggressive should I get with shocking etc to get this algae dealt with? Also, pool company usually adds shock during closing but if my FC hasn’t fallen much after shocking now what should I do at closing?
 
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If you are seeing algae you need to start the SLAM Process now. If your water temp is chilly it will work in your favor to slow the rate of algae growth and allow the FC to hold better. Best to eradicate any algae now by passing all 3 SLAM criteria before closing to help ensure a better opening next spring. But follow that SLAM Process page carefully. Good luck!
 
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Water is 57-59 but this has been after no sun and rain for last 4 days. I think rain is done so I ran a set of tests today and reasonably in check except FC is high so can’t test pH.

FC 14
CC 0
TA 80
CYA 60
Salt 2600

I guess I should’ve dialed back SWG once we stopped swimming but didn’t expect it to be this high.

If I SLAM now FC would be in low 20s at closing. Is that a problem to close with high FC? I have very little sun during the day this time of year so I don’t expect a lot of chlorine to burn off either.
 
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mrm1682 said:
I ran a set of tests today and reasonably in check except FC is high so can’t test pH.
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NICE catch !!!! (y)

Also, 'high' is over SLAM. 14 is GREAT and a head start on your low temperature algae battle. It should be alot easier now that it's not growing exponentially.
mrm1682 said:
I guess I should’ve dialed back SWG once we stopped swimming but didn’t expect it to be this high.
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The last week and a half or so, the UV fell off a cliff up here. Straight through the summer, two weeks into September I was cruising at 60%, 40% was week 3, 20% was week 4. October is using even less
mrm1682 said:
If I SLAM now FC would be in low 20s at closing. Is that a problem to close with high FC?
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We rec 2 ways to close:

1) SLAM / pass OCLT / close

2) SLAM / pass OCLT / drift down 50% / add polyquat / close.

Up to you which way you prefer. The mission is to have enough chlorine or polyquat to make it until the water stays cold. (We could be warm 2 weeks from now, you know how it goes 🤷‍♂️). Then you open early before the algae wakes up.
 
I appreciate the help. Not sure if this changes anything but I turned off my SWG last night after testing my FC and today it’s 13. So dropped by 1 after 24 hrs and nothing added to the pool. It was essentially clean but when I scrubbed it I did kick up some very light green/yellow dust but only in a few areas.
 
It's great that your FC level didn't seem to drop much, but based on the stuff you are seeing when you brush, I would maintain the SLAM FC level a little bit longer. Clear water and no visible signs of algae are part of the passing criteria. So unless you are finding a dust-like sediment around the pool or on your cars, it must be from in the water. I might also be concerned it is Mustard Algae which could require a higher FC level for a 24 hr period. But continue with what you are doing for now and let us know if there are any changes positive or negative.
 
Thanks. Will give it a shot. Thought I had mustard algae a few weeks ago (posted in algae room about it) but then it got better. I started SLAM today.

One other question - I’m using PB to close the pool again this year and I’m scheduled for 10 days from now. They usually add shock and algaecide at closing. Should I forgo the shock? FC loss is about 1 per day and this time of year basically have all shade over the pool. Can FC be too high before closing and cause a problem?
 
mrm1682 said:
Can FC be too high before closing and cause a problem?
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In some cases it can be. But a really high FC level can be counter-productive to any algaecide. Considering your very low FC loss per day, falling water temps, and very little sunlight on the water, you might just keep the FC in the upper value of your daily range. Let the PB close in 10 days and just start fresh next season.
 
Thanks. Woke up to crystal clear water today after starting SLAM last night. Hopefully nothing pops up this weekend or before closing.

If my FC is above 10 at closing my pH won’t be testable…correct? So how do I ensure water is balanced well enough before close?
 

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One last question -

I SLAM’d last week and haven’t seen any algae pop up since. SWG has been off and FC has slowly trickled down to 12 today. All other numbers are in range. PB is closing Monday and they said they and shock and algaecide (not sure which kind of either but pretty sure they said Cal Hypo but don’t know the percentage). Is it worth shocking with a FC 10-12? If it’s 73% cal hypo, poolmath estimates my FC to be in the 16-18 range. Will it be harmful to be that high? Is it even necessary?
 
mrm1682 said:
Will it be harmful to be that high? Is it even necessary?
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You can discuss the already elevated FC level with them when they arrive, but as long as your CYA is 40 or above it should be fine. You paid for the service, so I'd let them do it. Enjoy your weekend.
 
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