Lowest Ever TA - Explainable?

[DanF]

I just did a full test of my pool's chemistry, except for salt. I drained my pool just before Xmas and I won't run my SWCG for a while so I haven't added salt since then.

My TA result sort of opened my eye, so I tested twice to be sure. I have been using more MA than normal to bring pH and TA down after the refill, and I am using tabs to sanitize and slowly get the CYA back up. Here are my results:

FC 5.5
CC 0.0
pH 7.3
TA 40 (lowest ever)
CH 450
CYA 50
Temp 56.5F
CSI (1.00)

Should I be concerned at the low TA/pH/CSI? We have had a cold spell recently and air temps (and thus water temps) will be rising soon, which will drive up CSI. Also, I have not be using the auto-fill because of the rain and lack of evaporation, so once I turn that back on the chemistry will degrade on its own .

So am I Ok until this happens? IOW should I just wait it out or should I add some baking soda?

 

[JamesW]

I would raise the TA to 60 and then retest everything in a few days.

 

[DanF]

I would raise the TA to 60 and then retest everything in a few days.

Thanks James but I hate raising TA when I know I'll be fighting the rest of the year to keep it down.

 

[mknauss]

Quit using the trichlor. Use liquid chlorine if needed for FC.

 

[mgtfp]

Per 10ppm of FC that you add with Trichlor, TA gets reduced by 7ppm (once the FC has been used up).

 

[pjt]

I have been using more MA than normal to bring pH and TA down after the refill

You used too much MA. As you approach a TA of 50, reduce your MA additions and let the pH stabilize in the high 7s.

I am using tabs to sanitize

Tabs are very acidic and are counterproductive at this point. Is your water warm enough to operate your SWCG? If not, use LC.

My TA result sort of opened my eye, so I tested twice to be sure.

Are you continuing to add drops until there is no further color change? Most of the time, the test needs another drop or two after the initial color change.

 

[JamesW]

Thanks James but I hate raising TA when I know I'll be fighting the rest of the year to keep it down.

If you don't add it, the water will probably just get it from calcium carbonate in the plaster.

 

[DanF]

Thanks everyone. I'm gonna yank the tab floater out of the pool and go with FC for now. I thought I could use tabs (even knowing they're acidic) to help lower pH after the drain and to boost CYA. My SWCG won't work until the water warms up another 3-5 degrees.

 

[Newdude]

If it's too cool for the SWG, then daily demand is still little. Add the whole gallon for 8 FC and it'll last a week or more.

It's the same easy as the tabs with none of the side effects.

 

[DanF]

It's the same easy as the tabs with none of the side effects.

Yeah, I guess I didn't think the tabs would have that much of an effect on TA. Was using them to lower pH and raise CYA.

 

[mknauss]

Acid consumes TA when it lowers pH.

See Effect of Adding in PoolMath.

 

[Newdude]

Yeah, I guess I didn't think the tabs would have that much of an effect on TA

When you learn each lessen the hard way, they sink in more. Ask me how I know.

 

[Mdragger88]

The tabs weren’t a terrible idea persay but you must be aware of what they do & use them sparingly. It’s time to ditch them now unless you want to keep having to add soda.
I had a similar experience.
I was gifted some (a lifetime supply basically) so I was using them sparingly to help in the heat of summer with fc (i had an undersized swg) & to keep cya up. Free chlorine right?
I had to add baking soda for the first time in 8+ years! I still use them occasionally & for vacations but I watch the ta/ ph like a hawk. Generally my ph & ta never change so when that happened I was a bit caught off guard & definitely learned my lesson.

 

[DanF]

The tabs weren’t a terrible idea persay but you must be aware of what they do & use them sparingly. It’s time to ditch them now unless you want to keep having to add soda.
I had a similar experience.
I was gifted some (a lifetime supply basically) so I was using them sparingly to help in the heat of summer with fc (i had an undersized swg) & to keep cya up. Free chlorine right?
I had to add baking soda for the first time in 8+ years! I still use them occasionally & for vacations but I watch the ta/ ph like a hawk. Generally my ph & ta never change so when that happened I was a bit caught off guard & definitely learned my lesson.

Thanks md. I took the tabs out yesterday and will use LC until it's warm enough for my SWCG to fire up. Yeah I also have a backlog of tabs from pre-TFP days that I've been using sparingly (normally during the winter), but I think I may have gone a tad overboard this year. Also, PoolMath doesn't indicate that trichlor lowers TA like MA does; also I recall a post where one of the experts said trichlor doesn't affect TA much. In my case it was likely the combination of MA and trichlor that did it. Live and learn!

 

[Newdude]

It's always pool specific. Most have a higher TA and some have sky high TA fill water that balances it out if they're also in a higher evaporation area.

We can teach you the basics, but we always have to custom tailor them to you as well. I have a love/hate relationship with old threads. They can cause as much harm as they help, while being 100% correct for that OP.

 

[Mdragger88]

All acids lower ph & subsequently lower ta.
Its the constant feed of the tabs lowering ph/ta that’s hard to gauge in real time. You test & think to yourself that ph has stayed constant which is really not true- it was continuously rising but simultaneously being lowered by the tabs which also lowered ta. The ph rises back up on its own due to aeration/plaster but the ta doesn’t do this. Most people don’t introduce enough high ta water to counteract the effects of constant trichlor use.

 

[JamesW]

I recall a post where one of the experts said trichlor doesn't affect TA much.

Who said that?

Link?

 

[Mdragger88]

Also, PoolMath doesn't indicate that trichlor lowers TA like MA does

Maybe we can get that changed because it certainly does -
@Leebo I’ve got something to add to the list

 

[mas985]

My pool has been at a CSI of -1 many times during it's 18 year life span and I don't get very concerned about it because testing has shown that the etching rate at -1 is actually very very low.

The CSI is Reliable for Plaster-based Pools

Using the Calcium Saturation Index (also known as the LSI in the pool industry) as a guide for maintaining proper pool water balance and to protect pool plaster, including quartz and pebble finishes, has become a mainstay in our industry for good reason. Several experiments have been conducted...

www.troublefreepool.com

Plus we have high evaporation and high PH/TA/CH fill water so I am constantly adding acid to keep CSI in the negative range so if I overshoot, I just turn off the acid for a week and it bounces back pretty quick. Given the fill water conditions, I never deliberately raise PH/TA/CH because I know all will increase over time.

Chandler, AZ is very dry (high evaporation) and has pretty hard fill water, correct? It probably won't be very long before CSI rises on its own. If it were me, I would just monitor the CSI over the next couple weeks and see if it doesn't move higher on it's own. Just don't add any acid during this period.

 

[DanF]

Who said that?

Link?

My bad, James. It was a question about dichlor, not trichlor.
Couple of Dichlor Questions