Black Algae, Wire Brush, New Plaster

[edjanowsky]

I have a brand new three and a half month old pool and am so glad I found TFP.

The SWG isn't even close to keeping up so I guess my CYA 55 isn't high enough. The FC is .5 so I added a couple gallons of 12.5% shock at $5/gal today and plan on adding another after dark. Even though the water was perfectly clear. When should I add the conditioner?

I'm six blocks from the Gulf of Mexico so I'm thinking that's where the Black Algae came from. And with almost no chlorine and somehow phosphate at 500 this stuff could really take off. So I started reading and got out the wire brush, but now I see I shouldn't have done that on my brand new plaster???

The pH was 8.2 but came down somewhat after the two gallons of shock. I also have muratic acid but I'm not sure when to add it and especially considering I'm planning to add more shock which already brought it down some.

I have the Taylor K2006 test kit, but no degree in chemistry and the manual's pretty daunting.

I realize I'm all over the place here, but I definitely need more help than I'm willing to get from the local PS.

 

[AimeeH]

Welcome to TFP

Step one. Break out that test kit and post up a full set of results.

FC
Cc
TA
Ph
Ch

Pool School - Black Algae

 

[edjanowsky]

FC - 1
Cc - 1
TA - 80
Ph - 8
Ch - 300

 

[kcindc]

FC - 1
Cc - 1
TA - 80
Ph - 8
Ch - 300

First, you should bring down your PH to around 7.2 ASAP.

Eliminating algae isn't complex, but may take a little time and a little patience. Let's first see if you have regular algae that needs to be killed because your FC dipped way too low for your CYA. BTW, phospates are not something to worry about as long as you keep your FC above the minimum for your CYA: Pool School - Chlorine / CYA Chart

Second raise your FC up to SLAM level (see chart link above). CYA is always rounded up, so target FC=24 using plain liquid chlorine (plain bleach found at Wal-Mart is usually cheap and fresh). Use pool math listed at the top of this page to determine the amount to add. Once your FC is up to 24, conduct an overnight chlorine loss test to see if you have regular algae growing: Pool School - Perform the Overnight FC Loss Test (OCLT)

Here is a black algae article to read which states that the best way to deal with this is to have high FC levels and brush. Use liquid chlorine to keep your FC levels high as your SWG is good at maintaining regular FC levels, but will struggle to accomplish this:
Pool School - Black Algae

Don't raise your CYA until we have resolved your algae issues. Ask any questions and we'll be here to help you.

 

[edjanowsky]

What about using the stainless steel brush on my new plaster? Some articles say not to use steel for a year, and I can see where I've scratched it.

 

[edjanowsky]

deleting duplicate post

 

[jdoty1977]

I had a few spots last year that may have been algae. Not sure. But I used a Char Broil Cool Clean Brush and it came out no problem. Its a grill brush so it is small. And you have to get in and hold your breath. but it works if you are able. I would not use steel if you can already see scratches.

 

[edjanowsky]

Here are today's results.

FC - 10.5
Cc - .5
Ph - 7.2
CYA - 70

 

[edjanowsky]

Don't raise your CYA until we have resolved your algae issues. Ask any questions and we'll be here to help you.

I havn't added any conditioner and the initial CYA reading of 55 was from the PS. Yesterday I read it at 90, so today I added tap water to the sample and multiplied the result by 2 to get 70.

 

[edjanowsky]

Second raise your FC up to SLAM level (see chart link above). CYA is always rounded up, so target FC=24 using plain liquid chlorine (plain bleach found at Wal-Mart is usually cheap and fresh). Use pool math listed at the top of this page to determine the amount to add. Once your FC is up to 24, conduct an overnight chlorine loss test to see if you have regular algae growing: Pool School - Perform the Overnight FC Loss Test (OCLT)

Is it OK to swim in the pool with FC at 24 or even 28 with my current CYA reading of 70?

 

[kcindc]

Have you conducted the OCLT yet? That is very important.

Pool store CYA tests are the most notoriously inaccurate test result because it is a light sensitive test. Generally they just use test strips which are very inaccurate. Around here we call them "guess strips". Did you test it outside in the full sun, back to sun, vial at waste level when you got the 90 result? Diluting the CYA test is helpful to see if your CYA is higher than 100, but is less accurate when your levels are less than 100, so I would trust the non-diluted test.

Is it OK to swim in the pool with FC at 24 or even 28 with my current CYA reading of 70?

It is safe to swim when:

water is clear enough to see a person at the bottom of deep end
PH is between 7.2 and 7.8
FC is above minimum for CYA
FC is at or below SLAM level (FC=28 for your CYA)

- - - Updated - - -

I had a few spots last year that may have been algae. Not sure. But I used a Char Broil Cool Clean Brush and it came out no problem. Its a grill brush so it is small. And you have to get in and hold your breath. but it works if you are able. I would not use steel if you can already see scratches.

Using a non-pool metal brush on a pool can damage the very expensive finish of your pool and is not recommended.

 

[edjanowsky]

Have you conducted the OCLT yet?

No because you said to get the FC to 24 first, but that info was based on an unreliable PS reading of 55. So I did my own test yesterday outside in the full sun, back to sun, vial at waste level and got 90 and followed CYA Test step #8 to get 70 today.

So based on today's CYA reading, and Pool Math, I'll add a couple more gallons of 12.5% chlorine today and then check the FC at sunset and then again first thing in the morning even if FC still isn't 28 tonight. How's that sound?

- - - Updated - - -

Using a non-pool metal brush on a pool can damage the very expensive finish of your pool and is not recommended.

Are you saying this brush will be OK on my new plaster?

 

[kcindc]

OCLT tonight will be good. Make sure to test after the sun is gone and before the sun is up.

Yes, that brush will be fine. Don't go scrubbing super hard as getting rid of black algae takes time and high FC levels. That brush will help remove the biofilm that algae develops so that the FC can kill it. The biofilm protects algae from being killed by FC.

Once your black algae is gone you can switch over the wall whale brush which is great for maintaining a clean pool. https://www.amazon.com/Wall-Whale-Classic-Swimming-Brush/dp/B004VU92KE/ref=lp_1272984011_1_4?s=lawn-garden&ie=UTF8&qid=1497629364&sr=1-4

 

[jdoty1977]

I think that was my point. It is not metal, it is a nylon brush with much firmer bristles than the standard pool brush. But not as harsh as steel. I never found anything in between steel and soft nylon pool brushes.

 

[edjanowsky]

I ran the OCLT, but I did not add any 12.5% Chlorine like I said I would because yesterday's FC level was 10.5 which combined with the new brush seemed high enough to attack the black algae according to this Black Algae page.

However with the OCLT Complete 6/16 & 17 and showing the following results,

FC 3 (both times)
CC .5 (both times)

it seems clear I need to raise the FC level by adding a gallon of 12.5% to get FC to around 11 according to Pool Math and the Black Algae Page. Yes???

My other big concern is that the SWG may not be working. I run it 24/7 at 100% (it was off last night for OCLT) but somehow my FC won't stay up.

 

[edjanowsky]

Yesterday I added that gallon of 12.5% bleach, but this morning's readings are as follows.

FC 3
CC .5
Ph 7.6

So I've added another gallon of 12.5% bleach. (edit: this got FC up to 11 exactly as Pool Math predicted)

I need some help. OCLT shows good even though I definitely have some black algae. Could that and yesterday's bathing load and the sun be what used up a whole gallon of bleach even though I'm running my SWG 24/7 at 100%?

I sure wished I'd captured a return water sample before adding the bleach this morning. I'll try that in the morning but in the meantime any and all questions and suggestions will be greatly appreciated.

 

[kcindc]

Brushing the black algae may be using up your fc. Make sure you have enough bleach in hand to supplement your swg which is a little small for your pool.

Tfp recommends swg be 2 to 3 times the size of your pool. Otherwise you will need to run your pump 24/7 and have your swg set to 100 percent.

 

[edjanowsky]

Today's Readings

FC 3
CC .5
Ph 7.8

I've lowered the Ph and taken a sample from the return. FC shows 3.5.

 

[edjanowsky]

it seems clear I need to raise the FC level by adding a gallon of 12.5% to get FC to around 11 according to Pool Math and the Black Algae Page. Yes???

 

[kcindc]

Could you try doing the OCLT after bringing your FC to SLAM level? Your pool is a little new to have a problem with black algae. I think you might have a problem with too low chlorine since your SWG is too small.