Strategy needed: manage TA/pH or drain pool? Or something el

[rford_tx]

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
FC 0
TC 1
pH <7.0
TA 250
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)

 

[linen]

Re: Strategy needed: manage TA/pH or drain pool? Or somethin

Welcome to tfp, rford_tx

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?).

This is likely due to algae with your FC at 0 ppm. With cya as high as you indicated you need to have your FC at a very high level (likely much higher than 10 ppm FC) to remain algae free. You need to do a drain refill to lower the cya. To get a feel for how much, mix half pool water and half non-cya water then repeat the cya test then multiply your result by 2.

What is my strategy to fix the issues?? What should I do first…then second?

Reduce cya level to 50 ppm.

Do I attempt to resolve low pH with Borax and aeration treatment?

You should lower TA using the aeration method. No borax for now. I would not let your ph go below 7 ppm during the process.

If yes, How much Borax and how long aeration?

No borax for now. For aeration, as many cycles as is required to lower your TA down as far as you want. Lower ph when it reaches 7.8 to 7.2 using Muriatic Acid.

What is your CH level?

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)?

I am not sure, but I have heard purple may be manganese. What is your fill water source?

 

[rford_tx]

Re: Strategy needed: manage TA/pH or drain pool? Or somethin

Thanks. I am going to start a drain. I am concerned that my CYA has got out of balance again, only one year since I did a drain for the same issue? What reasons cause it to rise so rapidly? What actions will prevent this happening again?
Note: my hardness level seems OK at 250.

 

[linen]

Re: Strategy needed: manage TA/pH or drain pool? Or somethin

What reasons cause it to rise so rapidly? What actions will prevent this happening again?

The only way cya gets in the water is by adding stabilizer (also known as conditioner) or using trichlor or dichlor. Bottom line, you (or any other person maintaining the pool chemistry) put it in there, so after your partial drain/refill you can choose not to do that again. See: http://www.troublefreepool.com/pool-school/types_chlorine_pool

I would get a feel for how much you need to drain. If you mix 1/2 pool water with 1/2 cya free water (tap water is fine for this) and then repeat the cya test. The new value you get should be multiplied by 2 to get your pool's cya level. Post what you get.