Need some basic advice -TA, pH, CH, FC all things chemical

[SoDel]

Hi all, I took over managing my own pool this year. It was opened less than a week ago and with some brushing and vacuuming and filtering, I got lucky and water is already clear. Pool was managed by “trained professionals” in past years. The way they did it, pH always seemed high (8.0 is as high as I can measure and it was always 8.0, likely they let it get much higher as I never saw them add much of anything to the water), TA around 170 and CH between 200 and 250.

I want to reduce TA (to around 70) and increase CH (to around 450 or more) using what I remember of the Orenda method to “contain” pH rise while also keeping LSI in balance. Plan is to use HCl to lower TA and CaCl2 flakes to raise CH. So to the question — how should I go about actually doing this? All I can come up with is dilute about a quart of HCl into a bucket of water and add that in the morning, dissolve about 2 lbs. of CaCl2 and add that in the evening, repeat until levels are where I want them. Is this a good way to do this or how would you go about this? Thanks!

Current water test:
FC 3 ppm
TC 3 ppm
CC 0 ppm
TA 170
CH 200
pH 8.?
CYA 35
Salt 3,000 ppm

 

[Texas Splash]

how should I go about actually doing this?

First is the pH/TA. Use muriatic acid. Since your pH is elevated, lower it from 8.2 to 7.2. That large swing will help lower the TA. Once the pH rises back to 8.0 repeat. The TA will slowly come down each time. Easy stuff there.

For the CH, unless you have very soft water, I would only take the CH up to 250-300, especially right now while the pH and TA are a bit in "elevated mode" Do you use our PoolMath APP yet? If not you should. It has a CSI function which is programmed to do an outstanding job of keeping your plaster and SWG scale-free with a slightly negative CSI level.

Also be cautious of the FC and not let it get any lower or you run the risk of algae. Hope that helps. Welcome to TFP!

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[Flying Tivo]

Your CYA is 40, the scale is log, multiples of 10, round up. KeepFC/CYA Levels.
What is your CH and TA fill water?

 

[SoDel]

Hi, thanks for the replies! I haven’t tried PoolMath. Over the winter to get ready to take care of the pool this year I have been futzing around with the Orenda app and the Taylor SureTreat app. Will definitely try the PoolMath too. I sort of started out over the winter just “what if” futzing around with the Orenda app so I’m comfortable so far on that (I guess it’s my “Rosebud” app lol) but the more apps the merrier.

I am trying to get my FC higher but there is likely still a lot of pollen floating around in the water (my best guess for why it’s lower than hoped). Leads to another question — I have Hayward T-Cell-9 set to 85% and pump runs 10 hrs per day. Is there a chart somewhere that can tell me how much Cl it produces or ppm added to 15k pool? One pool maintenance company had it set at 35% for a season and another set it to 85% for a different season — both resulted in clear water but I don’t know what the Cl levels were.

I picked up 3 gals. of liquid Cl yesterday and plan to do a shock with that. I’ve been reading about the TFP SLAM process and may have a go at it but I’m not seeing any CC on the tests so might not do that now.

Fill water is from a couple years ago — came in a truck and pool servicer was in charge of that so I don’t know what it was. I topped up after this winter with hose water (city water) and I don’t remember what it tested at but I remember it was unremarkable for TA and CH. The sense I got from watching the prior maintenance companies is they didn’t do much to manage water chemistry — like pH always way high but LSI within range so they just let it ride that way.

 

[Flying Tivo]

This is not a Mix & Match program, you either do one or the other, but not both. It wont work. Up to you. In the PoolMath app you will find effects of adding, where you can find out how much SWG% you can use for your pool.

 

[SoDel]

I got the PoolMath and it did the job for figuring out the chlorine. Thanks for that! It helped me figure out and verify that I need 6 oz. chlorine gas to add 3 ppm FC to the pool. Long story short, PoolMath calculated the SWG I have needs to be 90% for the 10 hr. run time to make that much. I set it to 90% and I’ll let it run like that for a couple days and see where the levels go. I’d think / hope the FC demand isn’t a full 3 ppm every day when it’s not so hot out yet so assuming it’s not, I would see FC accumulate a little over many days time? Pool only gets full sun in the middle of the day.

 

[Texas Splash]

SWGs are very good at maintaining a set FC level as long as there is no algae. So be sure you are 100% algae free. If in doubt do an Overnight Chlorine Loss Test. SWGs are not good at increasing FC really high or fast. Plus, your SWG appears to be slightly small for your pool,, hence the 90% setting. So if you get in a pinch, add some liquid chlorine to boost the FC level. It's fine and might help avoid an algae bloom.

 

[MITBeta]

You will probably find, once you confirm you don't have to SLAM, that raising CYA to 60-70 is a SWG pool will help keep the FC you generate. See the FC/CYA Levels.

 

[SoDel]

I ordered 5 lb trichlor tabs and a floater. I figure it’s an easy way to boost the FC a little while also increasing CYA a little at a time? I also have 3 gal. 10% liquid chlorine in case of emergency

Side note, FC is up to 4 today (at about 14:30 hrs so during max sunshine) and CC is still 0. At least it’s going the right direction lol.

 

[MITBeta]

5lbs of Trichlor in 15kgal will raise CYA by 22ppm. Just watch your pH as trichlor is acidic.

 

[SoDel]

So a question — if no bathers are anticipated, why would we not raise FC to “ridiculous” levels — like between 50 to 100 ppm (which are typical for shock in water storage tanks) to reduce needed contact time versus lower “SLAM” levels to be laboriously maintained for just as effective longer contact time? I think I know this may be heresy but is there a “pool” reason to not just jack the FC to kill and oxidize the nasties in one swoop with a lot less work instead of monitoring every so many hours, etc.? The FC will float down soon enough. This is acceptable practice for potable water storage tanks and wells. Too cool for pools?

 

[Newdude]

This is acceptable practice for potable water storage tanks and wells

You don't have a $12k finish to worry about in storage tanks. They are not dyed a pretty color.

You equipment which also isn't cheap, is possibly unable to handle it also.

 

[SoDel]

You don't have a $12k finish to worry about in storage tanks. They are not dyed a pretty color.

You equipment which also isn't cheap, is possibly unable to handle it also.

Ok, but is there data to back this? I’d expect to see a short term pH rise and I understand I’m bucking the orthodoxy, but where is the data? Non-organic dyes should not be affected by chlorine. Are they in reality? Can pool equipment not withstand a short term rise in pH? What is the anticipated level of rise and for how long would we expect it to last? Could we not compensate for this with the addition of a calculated amount of acid? I don’t know the answers yet. That’s why I ask. Just saying no isn’t very helpful.

 

[SoDel]

I think there is a maximum FC I saw referenced as a % of CYA for bather comfort or maybe it was safety? It was a vague reference. Does anybody know what this (or those) max is and where it (they) comes from?

 

[proavia]

I think there is a maximum FC I saw referenced as a % of CYA for bather comfort or maybe it was safety? It was a vague reference. Does anybody know what this (or those) max is and where it (they) comes from?

See the FC/CYA Levels. It's not vague. It's 40% of CYA level.

 

[SoDel]

See the FC/CYA Levels. It's not vague. It's 40% of CYA level.

Yes, thanks. Where do the numbers come from? Is the reason for the number bather comfort or safety? Why for each? I’m curious (and not in the habit of blindly following oft repeated mantras). I’ve never seen a better collection of scientists brought together in common interest (swimming pools, why not) than on this site. Let’s ask the questions so we increase the level of understanding.

 

[Oly]

Let’s ask the questions so we increase the level of understanding.

Here are a couple threads from the Deep End of the forum, you may find more research here:

Chlorine/CYA Chart

EDIT: You will find a simplified and standardized version of this chart at Pool School, Chlorine / CYA Chart. Chlorine/CYA Chart by Chemgeek FC = Free Chlorine in parts-per-million (ppm) CYA = Cyanuric Acid in parts-per-million (ppm) CYA ........... Min FC3 ..... Target FC ...... Yel/Mstrd...

www.troublefreepool.com

Pool Water Chemistry

This thread presents my findings so far on pool water chemistry including the following: More Accurate Calcite Saturation Index (CSI) to replace Langelier Saturation Index (LSI) Calculation of ppm HOCl (disinfecting chlorine) at various levels of Total Free Chlorine (FC) and Cyanuric Acid (CYA)...

www.troublefreepool.com

If these threads don't answer your specific question then starting a new thread on the Deep End may be the best place.

 

[Newdude]

That’s why I ask. Just saying no isn’t very helpful.

Please ask anytime. That's how progress is made.

We have seen members of all finishes / pool types have them ruined from the pool store dump/pray methods. I don't have the answers for you as to where the problems start other than there are too many factors making each pool unique and we have to advise something safe for all of them.

Could you go to 100 FC without harm ? Possibly. We wouldn't know that everybody could also until they all tried it several times without harm.

It's a great question, with a nearly impossible answer.

 

[IceShadow]

When we removed the liner we replaced, it was as brittle as a potato chip. You could just take a piece and put your fist right through it and make a hole in it easily. It had gone from a vivid blue to almost pure white.

That’s what recurring shocks get you.

 

[Bperry]

It’s a fair question. I don’t have a vinyl pool but I’d read that those that do have to worry about chlorine bleaching the color. On the plaster side, the dyes may be bleached out. Is there somewhere I can go do read about non-organic dyes being unaffected by high levels of chlorine?