Is This Algae Or What?

by Rita

I have an 24' above ground pool. I put in a new liner and filled it with county water.

My pool levels are good, however, I am not sure what I have that forms in the bottom of my pool. It looks like grey clouds and when you sweep it, it just disentegrates into a cloud of smoke.

I vacuum with a pool rover and afterwards my pool looks great until 1-2 days later the stuff is back. Could this be algae or what?

Thank you.

Thanks for the question Rita

First, I'd like to have your complete chemical readings:

Chlorine, CYA (cyanuric acid/stabilizer), pH, Alkalinity, Calcium Hardness, and Metals (iron and copper).
It makes troubleshooting much easier and the process of clearing up your pool will go much faster. You can get this done at your local pool store. Without these numbers I'm just guessing at what the problem is.

I'd encourage you to get a Taylor FAS-DPD K-2006 pool test kit.

Pool Water Testing

Water Testing Kit

When you say country water does that mean well water? If so you'll want to get the metals in the water tested. Your problem could be algae, maybe yellow algae because it does tend to "smoke" up when it's brushed, but without the readings it's hard to tell.

Get back to me with the chemical numbers and I'm sure I can help.


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Jan 18, 2015
Not Sure About Chemical Readings
by: Rita

I am not sure exactly what I am doing but my readings from a pool store are as follows:
Test value:
free available chlorine 10.
total chlorine 10
combined chlorine 0
total alkalinity (adjusted) 118
ph level 7.6
calcium hardness 188
cyanuric acid 89
copper 0
iron 0
total dissolved solids 800
saturation index .04

The pool guy at the store said the cuanuric acid is high so switch to a nonstabilized primary chlorine sanitizer(Poolife 3" cleaning tablets instead of shock it).

He said the shock it plus I have been using can actually promote algae growth. Also, calcium hardness is low so add 5.5 pounds of calcium.
My pool is on county or the same as city water not well.

I hope this helps and is what he told me true?

Thank you.

Thanks for the readings Rita. It makes life so much easier for me.

First is the alkalinity. A bit high, but alright. I ran the pools on my pool route between 80 - 100, 120ppm being the highest, but you're o.k. with 118. pH is perfect so don't touch that. No pH up or alkalinity this or that. No baking soda/sodium bicarb.

You didn't need to increase the calcium. For plaster pools, I run them between 150 - 250ppm. Yours is a vinyl liner. The calcium hardness isn't that important.

Total dissolved solids (TDS) are fine. When they get to 1500 or higher you'll want to do a partial drain and refill. Copper and iron are great. What you have could possibly be yellow/mustard algae. It sweeps away like a cloud, then comes back within a few days. It's normally found on the shady areas of a pool.

Now for the chlorine and CYA. This is where many of these pool guys at the store fall short. Chlorine is the sanitizer for the pool, but you already know that. The CYA is the stabilizer for the chlorine, and you know that.

But, and this is the big but, that many pool owners and pool store guys don't know. There needs to be a balance between the CYA and chlorine. If you don't have this, the chlorine will be rendered ineffective (or less than fully active). Now, what is the balance?

The chlorine is 7.5% of the CYA and that level is 30 - 50ppm. What's your CYA level for a chlorine level of 10ppm, which you have. I will assume you've tried to maintain that because the question didn't mention about shocking the pool.

To get the CYA down you need to drain about 1/2 of the water and refill. It sounds like you may have yellow algae, as was stated, so a good shock should take care of it.

Yellow Algae

Shock in the evening, then retest in the morning. Be sure you're using a non-stabilized form of chlorine. Liquid is what I'd use. Go for 12ppm. A little over is better than under 10ppm.

Shock it again, then retest in the evening. If you need to shock it again, test in the morning. You should only lose about 1.0ppm of chlorine during the night. If you lose more, you probably still have an algae problem. Keep filtering 24/7 and brush as often as you can. Back wash the filter once a day.

You need to keep the chlorine level up above 12ppm for as long as you can. Remember that shocking is a process, not a name or an event.

With a vinyl liner, get a 5 gallon bucket and fill 1/2 with pool water. Put the chlorine in and stir with a PVC pipe or stick and broadcast that around the perimeter of the pool. Remember long sleeves, gloves, and goggles.

Brush the sides and bottom well to break up any hot spots. The yellow algae link has a chart you need for your size pool.

Hope this helps and have a great Summer.


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