High FC but algae won't clear up

[kmd]

Hi everyone - great board you have here. I'm hoping to get some help, I'm kind of at a loss here...

Using HTH test strips every few hours:

TH 200
FC 10+++ (the pad on the strip is so dark it's almost black)
PH 8.4 (it was stabilized at 7.2 before I shocked though)
TA 120
CYA 30-50

I have a 4-year-old 11,000 gallon above-ground pool and sand filter. I forget the brand of the filter but the handle has a W on it. The weather here has been overcast and cool, if that makes a difference.

Uncovered the pool on Sunday and the water was dark brown, worse than any other year so far. I got up on the ladder and started pulling out leaves. I think I got the bulk of them out but I can't see more than an inch into the water. Tested and adjusted PH, then started shocking.

Sunday afternoon I put 8 bags of calcium hypochloride 54% in, and by Sunday evening the water had improved to a murky dark green. Filter is running 24/7, pressure has remained constant at 4.

Sunday night I tested the water before bed and the FC was still off the charts so I went to bed and dreamt all night of a pool filled with dead algae by morning.

Monday morning went out to the pool at 6am and the water was still a murky dark green. FC was still off the charts but the shade of purple was ever so slightly lighter the night before. I added another 6 bags of shock and a gallon of algaecide. Spent most of the day on the ladder brushing the liner, pulling out some leaves and basically willing the algae to DIE.

By Monday evening the water had improved to a pea-soup green and I could see in about 2 inches deep. FC still off the charts at a very dark purple, almost black. Thinking more shock might speed up the process, I added another 6 bags and brushed the liner some more.

This morning I ran outside at 6am, thinking that HAD to work but the water has shown no improvement since yesterday... it's the exact same murky pea-soup green. The FC held overnight at a very dark purple on the test strip.

So since Sunday afternoon I've used 20 pounds of shock on an 11,000 gallon pool. Overkill? I know it's only been 36 hours but I don't remember it ever taking so long to show a marked improvement when I shocked. I live in the boonies and pool supply stores are a daytrip away so I'm relying on my test strips, my very basic knowledge of pool chemistry and the internet.

Any thoughts or advice? Thanks so much.

 

[JohnT]

Welcome to the forum!

You really need to know what your actual chlorine reading is. I'd try diluting the water sample with enough distilled water to get a reading that's in the range of the test strips. Try three parts distilled water (well water will do if you don't have the distilled) to one part pool water. Multiply the strip reading by 4 to get the actual reading.

You'd be better off with a test kit that can read the high chlorine levels you need for shocking.

Any debris in the water will make it hard for the chlorine to get to the algae to kill it. If you are truly getting to shock level, you will get it cleared if you stay at it, but my experience with algae is that the chlorine will not hold at shock level overnight.

Keep brushing and running the filter.

 

[The Mermaid Queen]

The test kit you want is either the TF100 (see my signature) or the Taylor K-2006. With anything less, you are really just tossing in chemicals randomly, kind of like what most pool stores have you do!! The TF100 will arrive in a few days!

Your pH may be high, which is not great - chlorine is much more effective at a lower pH range (7.2-7.4) HOWEVER, high chlorine causes most pH tests to read falsely high, so until you get a better test kit, ,eave that alone.

Heed JohnT's advice... keep shocking, brushing, and backwashing as needed, and keep scooping as much debris as you can!

Welcome to TFP! You will be swimming in no time if you heed our tried and true advice!

 

[duraleigh]

Welcome!

In years past, has your filter psi always been 4?

That seems a bit low and, while that's not the source of your green pool, it will help to know if you have a suction blockage of some sort.

 

[kmd]

Thank you for the quick replies!

JohnT, I diluted the water as you suggested and the FC reading was 28. I'm going to order a better test kit but I also want to keep on top of this while I wait for it to arrive, since I'm off this week. Do you think I should add more shock now? Or maybe I should wait and see what the reading is in a few hours before I add anything else?

 

[kmd]

Dave,

Last year the filter was running at around 7. I also noticed it seemed a bit lower, but the water seems to be circulating ok. I backwashed twice so far, but that's about all I know how to do. My ex-husband used to take care of the pool and filter so I'm new to this.

 

[JohnT]

Thank you for the quick replies!

JohnT, I diluted the water as you suggested and the FC reading was 28. I'm going to order a better test kit but I also want to keep on top of this while I wait for it to arrive, since I'm off this week. Do you think I should add more shock now? Or maybe I should wait and see what the reading is in a few hours before I add anything else?

I'd wait a few hours. Do you have good water flow out of the return(s)?

 

[JasonLion]

You want to keep FC above 15 at all times, keeping in mind that the test won't be at all accurate with dilution involved. Keeping the level high at all times by testing and adding more chlorine as needed is the key to beating the algae. If the FC levels falls the algae can start growing again, potentially wiping out any progress you have made to that point.

 

[kmd]

Ok, I'll keep scrubbing in the meantime. I also ordered the TF100 test kit; I hope it arrives soon. I'll report back if anything changes - thanks!

 

[kmd]

Hi everyone, I hope this update gets noticed - I'm not sure if I should start a new thread. Anyway, it's been a week since I opened the pool and the water has gone from dark brown to completely clear blue. It's still slightly cloudy but I can see the bottom very easily and there isn't a hint of green at all. Overall, I used 45 pounds of 54% cal hypo shock, 2 gallons of algaecide, various amounts of ph adjusters, and baking soda to raise the TA.

On Day 4 when I originally posted here and ordered my test kit, I added 25 more pounds of shock to the dark green water (for a total of 45 lbs in 4 days) and then left the pool alone for the next four days except for a few pump backwashes and some brushing. It gradually cleared on it's own while I waited for the test kit to arrive. Early this morning a test strip showed that my chlorine was down to 2ppm so I threw in a bag of shock as a precaution while I waited for the test kit.

Now I have the kit and my numbers right now are:

FC: 15
CC: .5
CH: 400
PH: 7.3
TA: 80
CYA: 0

So, things seem to be on the right track. The water is slightly cloudy but I imagine it will clear within the next couple of days. I'm a little concerned about my CYA level, as I don't want my chlorine burning off every day, but I worry about the CYA level getting too high. I have a container of stabilizer granules that I can put in and I'll aim for 30-50 but I'm not sure how well they dissolve or if they'll just sink to the bottom.

Anyway, I think my numbers look ok. If not I'm open to suggestions/thoughts. Thanks!!

 

[JohnT]

You did right keeping it in the same post. It comes back to the top of the page, and all the history is here to read. Glad things are looking better. You need to stop using the Cal-Hypo shock. Your calcium hardness is at 400pmm, and cal-hypo will add to that. How did you get the CYA test? Normally the test tends to read high in water that has any cloudiness to it.

 

[ivyleager]

Hi everyone, I hope this update gets noticed - I'm not sure if I should start a new thread. Anyway, it's been a week since I opened the pool and the water has gone from dark brown to completely clear blue. It's still slightly cloudy but I can see the bottom very easily and there isn't a hint of green at all. Overall, I used 45 pounds of 54% cal hypo shock, 2 gallons of algaecide, various amounts of ph adjusters, and baking soda to raise the TA.

On Day 4 when I originally posted here and ordered my test kit, I added 25 more pounds of shock to the dark green water (for a total of 45 lbs in 4 days) and then left the pool alone for the next four days except for a few pump backwashes and some brushing. It gradually cleared on it's own while I waited for the test kit to arrive. Early this morning a test strip showed that my chlorine was down to 2ppm so I threw in a bag of shock as a precaution while I waited for the test kit.

Now I have the kit and my numbers right now are:

FC: 15
CC: .5
CH: 400
PH: 7.3
TA: 80
CYA: 0

So, things seem to be on the right track. The water is slightly cloudy but I imagine it will clear within the next couple of days. I'm a little concerned about my CYA level, as I don't want my chlorine burning off every day, but I worry about the CYA level getting too high. I have a container of stabilizer granules that I can put in and I'll aim for 30-50 but I'm not sure how well they dissolve or if they'll just sink to the bottom.

Anyway, I think my numbers look ok. If not I'm open to suggestions/thoughts. Thanks!!

STOP using cal hypo, your calcium is getting a bit high. USE bleach. High calcium levels can cause cloudiness big time.

You can add CYA granules via the sock method....put in a sock and tie to your ladder or put in skimmer. They will disolve slowly. If you add the granuales directly to the water, their acid makeup can damage the liner. If you add the granules thru the skimmer you'll have to wait to backwash for about a week.

No need to use algicides............just keep the pool water sanitized with BLEACH....chlorine is a very effective algicide.

Did I mention to use bleach?

Hope this helps.

 

[kmd]

I used the black dot/cylinder test that came with my kit. The cylinder was completely full and I could still clearly see the black dot. My test strips have been giving me a 0 CYA reading as well for the past few days.

I suspect the cloudiness of the water is dead algae...? Or it could be some of the dust that keeps settling to the bottom of the pool and then getting stirred back up when I brush. Once I figure out how to get the vacuum hooked up I'll start tackling that.

What type of chlorine do you suggest I start using? I do have a large bucket of 3" tablets (with stabilizer) and keep one in the skimmer at all times but I suppose that wouldn't be enough chlorine especially with my 0 CYA.

 

[kmd]

Thanks, Ivyleager!

I'll switch over to bleach then. I noticed the term "skimmer sock" mentioned in some other posts here, and at the risk of sounding incredibly dumb, I have to ask, do you mean a regular sock as in Hanes tube socks? Or is "sock" some kind of pool term I haven't heard of yet. Thanks

 

[JohnT]

A skimmer sock is a fine mesh net that catches small debris before it enters the filter. It can reduce the need to backwash. The sock used for CYA addition is just a plain old sock.

 

[JasonLion]

I just pour the CYA slowly into the skimmer and then don't backwash/clean the filter for a week. That is simpler than getting a sock involved.