Surface algae on walls

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jeffbrig

jeffbrig

0
Sep 24, 2014
154
Fort Lauderdale, FL
Pool Size
15000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-15)
I've had my house w/in-ground pool for almost 2 years, started following TFP shortly after moving in, and haven't had any issues. Lately, I've been dealing with a light growth of light green surface algae on the walls of the pool in certain places - primarily on steps, and walls far away from my returns. Brushing (which I do pretty regularly, but not daily) removes most, but not all of the surface algae. The pool water continues to be clear - you could read a book laid on the bottom, or count the tiny specs of aggregate in the finish. And the pool is still blue, not a greenish hue. This is why I think it's really just surface algae - whatever is in the water column seems to be killed and filtered out quickly.

I've been dealing with this for a few weeks now. Brush, dose chlorine, pool looks clean for a few days, but then the algae patches return. Lather, rinse, and repeat. Last weekend my wife and I scrubbed every inch of the pool, and I dosed it good with chlorine. Maintained it at recommended levels (usually target 7ppm) during the week. On Friday, before heading out of town for Mother's Day, I brushed the sides again, and added a gallon of chlorine to put my FC at 10. Two days later, I come home to FC of 2, and light algae on the walls in the regular spots. Historically, my pool consumes only about 2ppm FC per day, so I would say my consumption is trending higher than normal.

Here were my numbers from this evening (TF-100):
FC: 2ppm
CC: .5ppm (barely any pink, cleared in 1 drop)
pH: 7.8
Ca: 325
TA: 70
CYA: measured 40-50, call it 50 (I deliberately keep it here due to strong sun)
Temp: 83 (ish)

I want the pool clean for Memorial day, so I've decided to hit it with a SLAM. Right thing to do? Heck, chlorine is cheap enough - $2.20/gal for 10.5% at my local pool store.

I started with enough muriatic to lower the pH to about 7.3. Gave that a half hour to mix, and added 2 gallons of chlorine, which I estimated to bring FC to a target shock level of 16ppm. Gave that another half hour and measured 17, all good there. I'll check it again in the morning and see what my overnight loss is.

Bottom line, if I pass the OCLT (not necessarily tonight), will I be able to break the cycle of recurrent surface algae?
 
Yes, SLAM is definitely the way to go. I had that last year, clear water, no CCs but a little slimy and higher chlorine consumption. SLAM went quick and cleared it right up.

Please add your state to your location in your profile, climate is often important when we help you with your pool. I would hate to assume your are in FL. We have someone in Dallas, GA and another in Houston, OH and Nashville is city in 8 different states.
 
It sounds like you could have circulation issues. You might consider adjusting your returns to see if you can improve water flow to those areas.

Are you getting strong water flow out of your returns? Has your filter been torn down and cleaned out recently.

Remember, a SLAM is only complete when you pass all three criteria. If you see or feel any algae in those affected areas, you're not done even if you pass the OCLT.
 
http://www.troublefreepool.com/content/128-chlorine-cya-chart-slam-shock
I totally agree that circulation could be part of it, but remember, your CYA of 50 means that anytime you let your FC drop under 4 in that spot, or anywhere, you're offering algae a free home. Your target FC suggestion is 6 but if you suspect a circulation issue maybe 7 or 8 would be safer? This is all after the SLAM of course, to really kill what has developed. Don't forget ladders, lights, and the pool toys and equipment!
 
pooldv, yes I am in florida.

It is quite likely that low flow/circulation plays a factor. My pool has only a 3/4hp pump, which is probably marginal for its size to begin with. I had to replace the motor last year, and despite it being labeled as a direct replacement (I guess physically it is), the new motor does not seem to move as much water as well as the old one. So it seems that is likely a contributing factor.

This morning, I tested FC at 19, which tells me two things. I probably wasn't fully mixed when I measured 17 last night (circulation, anyone?), and I probably didn't have much chlorine consumed overnight. Still had some little patches of algae on the walls, not much difference from last night. CC was still very low, barely a hint of pink showed.
 
It really does sound like you have poor circulation. If your FC is that high and green algae is still visible in those areas, then there's almost no circulation of water there. Diffusion of chlorine alone is insufficient - it takes hours upon hours of time for chlorine in unmixed water to diffuse even a few inches. You'll need to vigorously brush those areas to get chlorinated water there.

As for the motor exchange, did you replace the impeller as well? Is the impeller the correct size for the motor? Could the impeller be clogged with debris or broken?

Perhaps your old motor was uprated and had a larger service factor (SF) than the current motor. Do you have any info from the motor plates you can post?
 
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Re-pointing your return eyeballs can help immensely with circulation. The goal is to achieve a counterclockwise or clockwise circulation pattern with all eyeballs pointing in the same direction. If on direction generates more flow toward the affected area then that would help a lot. And brushing daily during a SLAM or weekly otherwise always with lots of things. Algae grows a sort of skin that makes it resistant to chlorine and brushing is necessary to speed exposing the algae to chlorine to kill it.
 
Joyful, I kept the same impeller when I replaced the motor. Same size, should have been a direct replacement - at least that was my thinking at the time. I snapped a pic of the old faded motor plate, and it was 3/4hp, SF 1.27. The replacement is also 3/4 and 1.27. Hmm... both are/were running at 230V.

Current motor:
Amazon.com : Century Electric USQ1072 3/4-Horsepower Up-Rated Square Flange Replacement Motor (Formerly A.O. Smith) : Swimming Pool Pump Parts : Patio, Lawn Garden

pooldv - part of the circulation isssue is that the pool is 15x30, with only two returns. One is missing its eyeball (that's on my list), and the other is frozen and I haven't able to move it. They are located at the long ends of the pool, and generally push counterclockwise. But there is no eyeball or return in proximity to the algae spots to help. So I'm kinda stuck with whatever the pool builder put in...probably 25 years ago. I'm not completely devoid of flow - I have enough to run a Barracuda suction cleaner without issue.

- - - Updated - - -

Home for lunch, and the chlorine is working - I do see less color remaining where the algae spots were. My timer had shut off the pump, so I adjusted the time and turned it back on....
 
With a missing eyeball return, the flow is going to be unbalanced because one return is essentially an open-ended pipe and the other return has a restricted orifice. If you feel by hand, does one return feel stronger than the other?

Based on your description, it sounds like the motor replacement isn't the issue (aside from possibly being a little under-powered).
 

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As a temporary fix until your eyeball arrives (if you're not getting one locally) maybe you could hang something that would help direct flow in the desired direction? Paddle, oar, plastic cutting board, plastic plate, beach shovel, etc. Nothing with sharp edges or glass. Ideally something that won't be too damaged by the pool and doesn't have nastiness to leach out.

I know this might not be TFP approved, but if it were me, once a day I'd pour 4oz of chlorine about 6 inches off the wall there, swirl with brush, then scrub the wall and floor.
 
Hey guys, just a quick update. We're making some progress. I had to report for jury duty yesterday, so the pool had to take a back seat. Last night the FC was at 7, so I gave it a good brushing and added more chlorine. I'm seeing less on the wall patches, but still some around the waterline tile. Pic attached... this one is specifically in the recessed bench area in the deep end.

20160511_124534.jpg

I also ordered an eyeball to replace the missing one - should have it before the weekend. I got in the pool last night, and moved the "stuck" eyeball. I figured it would either move, or I'd break it and end up replacing it. It moved. Flow seems better with where I have it pointed now. I also went to the missing eyeball, and jammed 2 fingers into the open pipe to partially block it. Seems like I got 4x the water velocity coming out vs the open pipe, so I think getting an eyeball in there is going to help a lot, and I'm sure it improved flow at the other return as well.
 
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It's not uncommon for people to use eyeball returns with different sizes in different returns to help balance the flow. So you put a more restrictive eyeball on the return closets to the pump and a larger orifice on the one further away. This can help even out flow rate differences.
 
jeffbrig said:
Hey guys, just a quick update. We're making some progress. I had to report for jury duty yesterday, so the pool had to take a back seat. Last night the FC was at 7, so I gave it a good brushing and added more chlorine. I'm seeing less on the wall patches, but still some around the waterline tile. Pic attached... this one is specifically in the recessed bench area in the deep end.

View attachment 47858

I also ordered an eyeball to replace the missing one - should have it before the weekend. I got in the pool last night, and moved the "stuck" eyeball. I figured it would either move, or I'd break it and end up replacing it. It moved. Flow seems better with where I have it pointed now. I also went to the missing eyeball, and jammed 2 fingers into the open pipe to partially block it. Seems like I got 4x the water velocity coming out vs the open pipe, so I think getting an eyeball in there is going to help a lot, and I'm sure it improved flow at the other return as well.
Click to expand...
While you have the new eyeball in your hand where it's easy to play with...

I discovered that 1/2" PVC fittings will friction fit inside my pool's eyeballs. So suddenly I am able to direct flow precisely where I want it. The eyeballs will only turn so far to the side, but now I'm able to send a stream of water into the dead zone above the steps. Want it to blown down into the deep, or up to aerate? Piece o'cake.
 
Brushed the pool last night, and again this morning. Just trying to ensure no film builds up to allow the algae to grow. Very faint discoloration on the wall where algae has been. Not really rubbing off anything at this point, so I'm not sure if it's possibly some mild staining of the plaster. Either way, the chlorine will work it out...

FC was down to 9.5 last night, CC <.5, so we're doing pretty well. I dosed another gallon of chlorine to shock level (16+). I'm not strictly maintaining shock level, I'm fully aware of that. For now I will just continue to hold the chlorine level high until the visible spots disappear, then I'll do an OCLT at shock level and see where we are. Return eyeball arrives today. Once I get that installed we'll see what happens with the improved flow velocity.
 

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