I could certainly use some advice...

[cblankes]

I've been reading the various forums trying to diagnose and find a solution to my problem. I think I have calcium scale buildup on my vinyl liner. Here are the details and test results...

I am currently running a Autopilot SWG. For the past 2 months I have been out of the country and my wife has taken over pool maintenance duties. Unfortunately she been listening to my neighbor and has been dumping two 1lb bags of POOLIFE Turbo shock (Calcium Hypochlorite 78%) every 5 days. The water is clean, but this is a fine layer of white covering the bottom of our pool (but not the sidewalls). Plus, there are several brown algae spots that I just can't brush away. I think they might be algal/scale deposits??

Here are my test results (I know I need a more comprehensive kit, so I have just ordered one) :

FC = 1.75ppm
pH = 7.6
TA = 130

I'm wondering if I add muriatic acid and lower my pH to 7.0, if that will help soften the gritty white layer so that scrubbing will be more effective. If that works, what are my next steps?

Any advice would greatly be appreciated. Thanks!

 

[JasonLion]

Welcome to TFP!

Getting a full set of test result should be a priority. What you are describing sounds a lot like calcium scaling, but without a CH level there is no way of verifying that. If it is calcium scaling, lowering the PH might well help, but again it depends on your CH level. If it is calcium scale using a sequestrant optimized for calcium would also help.

Likewise, it is difficult to say anything about algae being a possibility without knowing your CYA level. Your FC level is fairly low for most plausible CYA levels, but could be alright depending on what CYA is.

 

[cblankes]

So I have just got my TF-100 test kit and here are my numbers...

FC = 1.0
CC = 0.0
TC = 1.0
pH = 7.8
T/A = 130
CH = 290
CYA < 20

Again, I'm running a SWC (Autopilot) and have an in ground vinyl pool (18 x 36 oval). I took a picture of an area where I've been able to brush off some of the white layer. (You are looking down the side wall to the deep end). The white layer is not on the side wall, but starts where my liner becomes patterned.

So what is your advice? Bring my pH down to 7.2 to see if that loosens the scale?

Thanks in advance.

 

[cblankes]

I had to resize the image. Here it is...

 

[JamesW]

Based on your numbers, calcium scaling is the most likely answer. Calcium hypochlorite does not dissolve well when the pH, TA and calcium are all so high and will create the white precipitate that you are experiencing. If you need to shock in the future, you should use liquid chlorine.

You should lower the pH to 7.2 and keep it there until your TA gets down closer to 60. Once your TA gets to 60, then you should maintain the pH at about 7.5 to 7.6 and you should get the cyanuric acid up to about 60 to 70. Maintain the FC at about 7.5 % of the cyanuric acid level.

The brown spots are probably iron. You could try ascorbic acid to see if it removes the spots.

 

[cblankes]

The brown spots are very slippy to the touch. When I vacuum over them I pick something up because the spots become darker. I think I suck up some lighter brown algae leaving the darker spot below. I've tried the ascorbic acid in a sock to no avail.