Copper Questions

[QPSUtah]

The TA is reported as 80, but I suspect that that is after someone found a negative TA and adjusted it with baking soda.

In my opinion, the pH probably went below 3.0, but this is just speculation based on the information provided.

I guess I’m trying to understand why I would use TA to calculate pH rather than doing a base demand test directly with pH. Is that only necessary when TA is 0 or negative? Or is it because the tables in the test book only seem to address pH values of 6.5 and above? Btw, does each drop of base demand correspond to a fixed increase in ph in the sample? What is that value? The tables in the back of the Taylor booklet seem to be quite linear in the range presented, so my guess is yes.

Trying to crystallize or simplify this to an SOP for my techs in the future. Looking at the base demand tables for pH there seems to be a linear relationship between drops added and

Also, Is the LSI a good value to look at as calculated by Orenda app?

 

[JamesW]

I guess I’m trying to understand why I would use TA to calculate pH rather than doing a base demand test directly with pH.

As a service person, you will encounter many different complex chemistry situations and you should have multiple different ways to understand the chemistry you encounter especially when the values are way outside the normal ranges.

Different techniques will apply in different situations.

Is that only necessary when TA is 0 or negative?

A 0 or negative TA is a special case that is not addressed by the normal testing procedure.

Is the LSI a good value to look at as calculated by Orenda app?

Some calculators use Total Alkalinity and some use Carbonate Alkalinity.

As long as the calculation is done correctly, most calculators should give roughly the same answer.

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[QPSUtah]

As a service person, you will encounter many different complex chemistry situations and you should have multiple different ways to understand the chemistry you encounter especially when the values are way outside the normal ranges.

no doubt. Thanks for all your insight. I’ve previously read through all those posts and they’ve been very helpful. Really helping me re-think how I want to provide service to my clients. But I’ll revisit them as well as the videos you sent.

Regarding my question on each drop of base demand corresponding to a fixed ph increase, I assume it’s linear, but also dependent upon TA, but one could still extrapolate out by measuring how many drops it takes to go from 7.2 to 7.6 on the color chart, and extrapolate back to an estimated start point if you’re needing more than 10 drops (though the sample volume may not actually accommodate more than 10 drops with the full sample size).

 

[JamesW]

For a pH above 4.5 and below the color samples, you can use base demand to calculate the amount of base required to recover.

However, I would never use sodium carbonate for anything.

Just use baking soda because it is much safer.

Carbonate will cloud and cause problems.

For example, if the Base Demands called for 51 oz Sodium Carbonate, use 81 oz sodium bicarbonate instead.

 

[JamesW]

For a TA below zero, you need to increase the carbonate alkalinity to about 60 and then allow the pool to recover by offgassing CO2.

For example, if the TA is -100 and the CYA is 150, then you need

100 + 60 + (150 x 0.333) = 210 ppm increase in TA, which should result in a TA of 110 and a carbonate alkalinity of 60.

The high CYA will require at least 50% drain and refill, but the pH will go from about 2.7 to about 6.7 immediately and to over 7.2 in 24 hours.

A pH of 2.7 is 10,000 times more acidic than a pH of 6.7.

The immediate goal is to get the pH out of the danger zone using baking soda while you plan for the next step, which will usually be a full or partial drain and refill.

 

[Mdragger88]

I have them currently switched to dichlor for the moment. It is an inground spa so SWG is an option for them (they have one for their larger pool). I agree, Bromine might be a good option for them.

Dichlor is also quite acidic and about 50% cya so not a much better alternative if they are blindly dosing without regard for ph.
Once cya gets to 30/40 they should switch to liquid chlorine.

 

[JamesW]

Here is a video about baking soda in case a customer asks where does baking soda come from.

 

[JoyfulNoise]

Here is a video about baking soda in case a customer asks where does baking soda come from.

You can make A LOT of pancakes with a 55lbs bag of baking soda !!

 

[QPSUtah]

For a TA below zero, you need to increase the carbonate alkalinity to about 60 and then allow the pool to recover by offgassing CO2.

For example, if the TA is -100 and the CYA is 150, then you need

100 + 60 + (150 x 0.333) = 210 ppm increase in TA, which should result in a TA of 110 and a carbonate alkalinity of 60.

The high CYA will require at least 50% drain and refill, but the pH will go from about 2.7 to about 6.7 immediately and to over 7.2 in 24 hours.

A pH of 2.7 is 10,000 times more acidic than a pH of 6.7.

The immediate goal is to get the pH out of the danger zone using baking soda while you plan for the next step, which will usually be a full or partial drain and refill.

We already drained and refilled to eliminate the CYA. So starting fresh at this point.