Algae in my above ground pool

[bioguy]

Hi all,
I've been lurking here for a couple of years. We finally got a pool last year.
Pool: 21 foot diameter above ground, 52 inch, appx. 4 foot deep. (appx 11,500 gal.).
1.5 HP Blue torrent pump
PRC 90 filter (also Blue torrent)
I got a chemical kit from TFT. Here are my numbers:
FC = 20 ppm
CC = 0 ppm
TC = 20 ppm
CH = 200 ppm
TA = 120
CYA = 65
The regular Cl test shows above 5
pH = 6.8
Temp = 85 F
Water is green.
I have two filters that I have been switching between so I can wash one and have the other one running.
Pressure in the filter is 10 psi and doesn't seem to rise above that even when the filter is full of algae.

Thanks for any help you can give me.
-David

 

[frogabog]

Are you 100% sure about the CC number? Your sample is clear after adding the 5 drops? Are you ever seeing blue cloudy water?

 

[Texas Splash]

Hi David and welcome! We typically round-up the CYA when it's halfway, so consider it 70 which means you need your FC to be 28. See FC/CYA Levels. Other than that, follow the notes on the SLAM Process page for best success. Consistancy in pool brushing, filter cleaning, and FC maintenance are key.

Once the SLAM is over, make sure to double-check that pH. It's a bit too low, especially since an FC over 10 usually makes it look higher. So validate that later. Good luck!

 

[bioguy]

I ran the test again (3rd time).
After adding DPD powder (R-0870), it turns a dark pink (almost red)

40 drops of R-0871 solution turns it clear.

After 5 drops, it was a very faint pink this last time (possible I saw it as clear the last 2 times)

I added 1 drop of R-0871 and it tuned clear again.

No, I didn't see any blue cloudy water.

 

[frogabog]

That means you have .5ppm or less CC. Typically that's ok.

But your water is green.

When and after what you added did the water turn green?

Can you post some pics of the water?

 

[bioguy]

So according to Texas Splash, I need more chlorine. That's good to know because I was afraid it was too high.

I'm not sure how to take a good picture of the water.
This one kind of shows the color.

This one kind of shows the color and how far down you can see.

When I am in the water, I can see things down 2.5-3 feet before they disappear.
I'll try to get better pictures tomorrow.

As for what has changed:
from last year to this year, quite a bit.

No longer using Frog Leap system that was installed since folks on the forum generally don't recommend it.
Opened the pool in May. We're in NJ. We lost a lot of water because rain on top of the winter cover pushed the water underneath out the inlet. I learned that I should have pumped that excess rain water off. I had to add some water. We have a well, and the water was very cold (55F), so I got a solar blanket and added a diy solar water heater (coiled black pipe) after the filter. The heater has been off since the pool hit 80, but I keep the blanket on when we're not swimming.
First started to have algae problems around Memorial day.
Added a lot of bleach and the algae went away for a while.
I also have an aquabot pool rover. When there was only a little algae on the bottom, it seemed like the rover made the water more turbid. I assumed that that was just because it was mixing stuff off the bottom. The rover seems to do a good job getting relatively big stuff off the bottom, but I think it just mixes the algae.
When the algae came back, I got a water testing kit from Walmart to test more than just pH and chlorine. The test showed I had no cya, so I added some. I thought I added half as much as I needed to get to the low end of the recommended cya. The new kit shows higher levels than I thought I had added.
I'm using Chlorox Pool & Spa Active 99 Chlorine Tablets (which are 99% Trichloro-S-Triazinetrione) for my chlorine.
I've been running the filter 24h/day.

I don't know if any of that helps. The details of what happened when are not really clear in my mind. I should write these things down.

 

[IceShadow]

Can you drain and refill half your water? That will get rid of some of the algae and bring CYA down to a more manageable level.

 

[bioguy]

Dustin - I'd rather not replace half of the water, but I can if I need to. We're on well water, and there is no water shortage here, so the only real cost to me is electricity to pump the water out of the ground. I'll do that if folks here generally think that's a good idea.

 

[mknauss]

If you discontinue all use of trichlor (the pucks you are using), you can tackle this with liquid chlorine. You will go through alot of it.

 

[IceShadow]

It’s up to you. If you have a good, reasonably priced source of liquid chlorine, you can make CYA of 70 work.

Get the chlorine up to SLAM levels. Test frequently (at least 3 times a day and up to once an hour) and keep pushing the chlorine levels back up as the algae eats it. You can either recirculate until the pool turns blue and cloudy or filter to try and get a head start on removing the dead algae. Brush and vacuum as much as you can. Get anything out of the pool you can - ladders, steps, etc.

 

[bioguy]

So the extra cya came from the pucks. Off to Walmart to get liquid bleach.
I've looked online for sources of bleach, but they don't seem to publish the % sodium hypochlorite on most sites (Amazon for example).

 

[IceShadow]

It's really inefficient to buy liquids online. They're very heavy for the shipping costs. See if you can get the 10% liquid chlorine from Wal-Mart - they typically have it in their pool areas.

 

[CarolineM]

I see in your picture you have a ladder/stairs in your pool, pull those out and clean them well with bleach. Algae hides in them. I would leave them out for the SLAM

 

[bioguy]

Drained 2/3 to 3/4 of the pool and added water from the well back.
Added chlorine (10%) approximately 200 oz (a jug and a half).
New numbers:
FC = 27
CC = 0
TC = 27
CYA = 20-30 (was about halfway between). Pat says round up, so that's 30.
CH = 225
TA = 200
pH = 7.5
Chlorine >5 (next time, I'm not going to do this test if I know it will be off scale)
Temp = 72 F.
The water is crystal clear.

So at this point, I think I should keep FC above 12.
I'd take the steps out, but I wouldn't be able to get in to brush.

One thought I have about the FC and CC tests - if you overshoot the FC test, your CC will be off. When I did FC, the tube turned clear, but when I let it sit for a minute, it turned back to a faint pink. So I added another drop of R-0871 to turn it back to clear. If I had gone ahead and done the next test, I would have needed a drop of R-0871 to make it clear. My FC would have been 26.5 and my CC would have been = 0.5. I guess this is a difference that really doesn't matter.

Thanks for the help.

 

[mknauss]

but when I let it sit for a minute, it turned back to a faint pink.

Once the test sample turns clear, the test is complete. Proceed to the CC test or dispose of the sample.

 

[IceShadow]

Don’t bother going above 12 FC with CYA 30. It’s wasteful and can damage pool surfaces. Just get it back to 12FC as often as possible during the SLAM.

 

[bioguy]

Will do. Really didn't intend to go to 27.

 

[bioguy]

When SLAMing, how clear is clear? I had no overnight chlorine loss last night, combined chlorine is 0.5. I can see my feet through 4.5 feet of water. They are slightly hazy. I guess it can't hurt to keep the chlorine up at 12 for a couple more days to see if the water gets any clearer.

 

[RonsPlc]

Clear is when you can tell if a dime is heads, or tails when it is sitting on the bottom of the pool.
Some people have better eye sight than me, and can read the date.

 

[Lilypad]

Crystal clear. When the pool water is completely still it should look like there isn't any water in the pool. High Definition water is what I call it!