Very slight amount of algae - shock or not?

[phalcon51]

Hey everybody,

I've been away from the forum for a while since everything seemed to be trouble free. ( that's the point, right? )

Over the Memorial Day weekend we were gone for 5 days. When we were about 100 miles away I realized I hadn't balanced the pool water before we left, and it had been at least 4-5 days since I had last checked it. When we got back, the FC level was 1, the pH was way above 8 and the CYA was only about 30 ( I had meant to build that up to 60 or 70 but procrastinated too long).

Last week I noticed a little bit of algae growing around the light bezel, on some of the plastic pieces in the pool such as the inset floater-rope attachments on each side of the shallow end, on the The Pool Cleaner vacuum unit and on closer inspection inside the vacuum hose as well. It was most noticeable in the Zodiac leaf catcher, on the plastic strainer and on the inside of the clear plastic housing. It sits just under the surface with still water in it most of the time when the vacuum is idle.

I adjusted the pH down to 7.4 (it took 3 days of adding 32 oz of acid per day [20 Baum - 31.45%]) and bumped the FC up to 11 and let it drift down to about 3.5.

Here are my questions:

Do I need to shock the pool at this point? ( haven't seen any further growth of the algae and the weather has been between 75 and 85 degrees F) If so, what should I raise the FC to and for how long?

I pretty much filled the hose with a strong solution of chlorine (43 oz in 4-5 gal. of water) and sloshed it back and forth for 4-5 minutes, which I think is sufficient to kill anything is the hose. The hose still had light deposit of green inside. Should it have been bleached to white if it was all killed?

What's the best way to remove the algae from the light bezel? Just a stiff brush or something stronger like a SS brush?

Do I need to worry about algae growing in the filter?

Here are the latest test results from about 10 min. ago. (using the Taylor FAS-DPD test kit)

FC = 6 ( had the SWG cranked up for the last couple of days )
pH = 8 ( I seem to have to add 16 to 24 oz. of acid at least twice a week to bring it down to 7.5. Any idea why so often? )
TA = 90 ( had it down to 60 back in mid-Feb. Would the quickly rising pH cause the TA to rise that quick? )
CH = 400 ( I drained and refilled to get it down to 250 back on Jan. 26. What would cause it to rise so quickly?)
CYA = 45 ( I still need to add a little over 4 lbs of conditioner to bring it up to 70 )
Salt = 3800 ( a little high - ideal is 3400 )
Temp = 82f
CSI = 0.35 ( seems ok? )

Thanks for the help.

Gary

 

[BoDarville]

Do I need to shock the pool at this point?

Is your water clear or cloudy. What are your CC's? I would also perform an Overnight FC Loss Test to determine if you need to continue the Shock Process.

Do I need to worry about algae growing in the filter?

Algae needs sunlight to grow, so no need to worry abut it growing in the filter. Plus, if FC is maintained, any surviving algae pulled in from the pool will be killed.

What's the best way to remove the algae from the light bezel? Just a stiff brush or something stronger like a SS brush?

Try a plasic-bristled brush first. If that doesn't work, then try SS brush. Always try the least invasive approach first.

pH = 8 ( I seem to have to add 16 to 24 oz. of acid at least twice a week to bring it down to 7.5. Any idea why so often? )

Do you have any water features (e.g., waterfalls, spillover spa, fountains)? If so these aerate the water thus causing pH to drift up.

CH = 400 ( I drained and refilled to get it down to 250 back on Jan. 26. What would cause it to rise so quickly?)

Water evaporates, buut calcium does not. Whenever you top off you pool, you are adding calcium that is present (to varying degrees) in your fill water. From what I have read, So Cal tap water is high in calcium.

 

[phalcon51]

Thanks for the quick reply.

Is your water clear or cloudy. What are your CC's? I would also perform an Overnight FC Loss Test to determine if you need to continue the Shock Process.

The water is perfectly clear, the only places I saw any algae at all are the ones mentioned above.
I'll check the CC's tomorrow and post the results.
I'll also do the Overnight FC Loss Test tomorrow night and post it on Mon. AM.

Do you have any water features (e.g., waterfalls, spillover spa, fountains)? If so these aerate the water thus causing pH to drift up.

No, none at all, just a variable speed pump that runs from 9 am to 11 pm at 1350 rpm except for 2 hours at 2200 rpm.

Water evaporates, but calcium does not. Whenever you top off you pool, you are adding calcium that is present (to varying degrees) in your fill water. From what I have read, So Cal tap water is high in calcium.

Yeah, it is somewhat high. My tap/fill water measured in at 160 ppm, but it's hard to believe that it evaporated that much water in less than 6 months, and the cool months at that, late Jan. through mid-June. Anything else that can cause it to rise that quickly?

Gary

 

[Butterfly]

The SWG creates aeration and in turn, causes the pH rise.

 

[phalcon51]

Is your water clear or cloudy. What are your CC's? I would also perform an Overnight FC Loss Test to determine if you need to continue the Shock Process.

I tested the FC and CC this morning and here are the results:

FC Decrease = .2 ppm

CC = .2 ppm

With those results I guess I don't have to worry about anything growing at the moment. I put some more conditioner in a sock a couple of days ago to continue bringing the CYA level up. When it's introduced slowly like that how long do you have to wait after the last of it's gone before you can get an accurate test?

My pH is 8.0 which I'm adjusting down to 7.4 at the moment.

BTW, is it high FC which skews the pH readings or the other way around?
Whichever one it is, what's considered "high"?

Also, I guess I'll have to live with the increasing CH levels as I really can't afford to be partially draining and refilling to bring it down too often. How high can I safely go if I keep all the other chems within their normal ranges?

Gary

 

[SkyKid]

over 10ppm of chlorine skews the ph reading is what I have learned here

 

[Butterfly]

^^^what SkyKid said.

I tested the OCLT and CC this morning and here are the results:

OCLT - .2 ppm

CC = .2 ppm

With those results I guess I don't have to worry about anything growing at the moment.

I don't understand the OCLT results. The OCLT is testing FC & CC at night after the sun is off the pool and testing again for FC & CC the next morning before the sun is on the pool. This test, by removing any possibility of sunlight, shows whether or not there are still organics in the pool.

 

[phalcon51]

I don't understand the OCLT results. The OCLT is testing FC & CC at night after the sun is off the pool and testing again for FC & CC the next morning before the sun is on the pool. This test, by removing any possibility of sunlight, shows whether or not there are still organics in the pool.

Sorry, that should have read "FC Decrease = .2 ppm"

I edited the original message to correct this. Thanks for pointing it out.

Gary

 

[savela]

I had this issue recently. CYA was too low (pool store told me it was 'perfect') and FC was drifting into the 1-2 range and I started to see small areas of algae in the corners of my steps, around my light and decided to not shock but simply spot treat. Despite crystal clear water and good test results (did not do overnight loss test) I decided to shock because I started to see a lot of water boatman in my pool. Decided that even though I couldn't see it, my pool was likely on the verge of an algae bloom. Good news is that once I decided to do it, it only took me 2 days to realize a zero overnight loss. I have since bumped my CYA to 60-70 (SWG) and my FC to 5-6 and sleep much better at night....and not a single boatman in sight

BTW, how did you calculate a FC loss of 0.2? 20cc for the chlorine test?

My vote is to shock before bumping your CYA any further and brush brush brush.

 

[phalcon51]

BTW, how did you calculate a FC loss of 0.2? 20cc for the chlorine test?

My vote is to shock before bumping your CYA any further and brush brush brush.

I used the Taylor FAS-DPD kit where it says to use 25 ml of water, add 2 dippers of R-0870 DPD powder and then count the drops of R-0871 titrating reagent till it becomes colorless. The first test, at sundown, took 17 drops for a reading of 3.4 ppm FC. The next morning, just after dawn, it took 16 drops for a reading of 3.2 ppm FC. Simple math from there. And, to be honest, the first test was a little equivocal. The 17th drop, I think, removed a minuscule amount of pink in the sample. It may have actually been essentially clear on the 16th drop.

Btw, I use the Taylor Speed Stir for all my tests. I believe it keeps everything a little bit more consistent than swirling by hand.

As to the CYA, I've already added another 3 lbs the day I took the 2nd FC test. I'm waiting for the weekend to take a reading. I believe it should be somewhere in the 50 - 60 range. I started out with it at about 45.

Gary