Background: About one year ago, I had the pool completely drained and acid washed (first time since built in 2006). Two reasons: 1) a ‘purple’ colored pool stain had developed on the pool bottom and walls and 2) CYA had become very high (>200). Since the start of this year, I’ve been unable to get the pool chemistry balanced.
Part (or possibly all?) of the problem may be related to the gas heater. The service light came on and it had developed a small leak. I had a pool service company examine the unit. They stated the unit was effectively dead and not worth fixing and so they disconnected it and rerouted the plumbing to bypass the heater entirely. With the dead heater standing isolated, water has since leaked out and left what looks like ‘rust’ colored stain on the concrete pad. Something inside rusting away?
Current : As for the pool, I’ve been struggling with very low ph and high TA. I've got into a vicious circle of adding acid to lower TA (into 100-120) and then struggle to get pH back into a normal range. With a Taylor K-2006 kit, pH reads below the 7.0 mark while TA is back into 250 level. I have managed to get TA down to about 120 but struggle to get pH back above 7.
To further confuse me, I took pool samples to 2 different pool shops to test water (both samples tested within 30 minutes for each other). Both shops had my pH as very low (one at 5.0, the other at <6.2). This confirms my test kit of very acidic pool water. However, the TA and CYA results were at opposite ends of the scale. One shop had it at TA 85 and CYA as 45….the other shop TA 175 and CYA 100!!! When the service company bypassed the heater, they quoted the CYA as 70. I measure the CYA as high due to the ‘black’ dot vanishing very quickly after just a few drops in the test kit.
As for Chlorine, I've turned off my automatic dichlor feeder and am using bleach. The chlorine levels are low and am unable to keep chlorine in the pool for very long (is this due to high TA or low pH or combination of both?).
So, moving forward the real answers I need are:
What is my strategy to fix the issues?? What should I do first…then second?
Do I attempt to resolve low pH with Borax and aeration treatment?
If yes, How much Borax and how long aeration?
Do I need to empty or partially drain the pool again (less than 12 months since last time) to bring CYA back in control? If yes, which CYA measurement do I trust?
In addition to all these issues, I have not been given a good answer for the purple pool stain…some have said copper (copper cyanurate, ‘purple haze’)….others have said manganese? The purple stain has colored the plastic parts of the Polaris cleaner but I can 'remove' the stain with diluted acid. All pool measurements for metals have been low. Could the ‘dead’ heater been the ultimate culprit (corroded coils)?
Current kit readings
CYA high (no more than 8 drops)
In-ground pool, built December 2006, 16,000 gallons with ‘Diamond Brite’ finish, Polaris Watermatic Granular Dichlor Feeder System
Pentair Gas Heater (disconnected and not working)