Brian & Dorie, Phoenix

[B&D]

I'm unsure what to add for targets. My first instinct is to go with the lowest number recommended but I really don't understand yet the relationships, cause/effects of the chemicals.

Targets
pH= 7.5
FC= 3
TA= 70
CH= 250
CYA= 30

 

[JasonLion]

Most of the numbers tend to drift one way or another. So typically you wait till they are at the end of their range and then adjust them to the other end of their range. For example, CYA invariably goes down very slowly, so you would normally adjust CYA up to about 50 at the start of the season and then by the end of the season you should end up around 30. Likewise, PH tends to go up, and when it gets to around 7.8 or 7.9 you bring it back down to 7.5. However, in a few pools PH tends to go down, in which case you would adjust the other direction. CH usually goes down over time, though if you are in a hot dry climate it can go up. Once you figure out which your pool does you can adjust towards the other end of the range. TA will tend to move in the opposite direction from PH, if PH tends to go up, TA will tend to go down.

 

[Bama Rambler]

I usually set my targets in the middle of the recommended goal range (I.E. if FC for my CYA calls for a goal of between 3 & 7 ppm I set my goal at 5ppm.)

I run my CYA (stabilizer/conditioner) at 60 ppm because I get full sun on the pool all day. Right now it's 35 but that's after winter and I'll raise it in a few weeks.

 

[B&D]

Thanks guys!

I want to borate my pool after I get my numbers right and stabilized. What effect would doing that have on the chemicals I add now, at the beginning? Can I use the pool calculator and my TF100 test kit to get borate numbers now?

 

[zea3]

Read the first few posts in So you want to add Borates to your pool and use the google search at the bottom of the page for specific questions. If you can't find what you need in that thread then post your question and we'll see if we can find the answer.

The directions are simple to follow. I did it last year and loved the results! We had a few really big rains over the winter and most of my borates are gone so I need to redo mine. Always shoot for a little less than you think you need. It is much easier to increase levels than to drain to lower them.

 

[It's pooler in AZ]

I have made notes to myself over the years as followed:

Cal-Hypo increase Calcium Hardness (CH). Trichlor or Dichlor increase CYA.

For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by 7 ppm.

For ANY source of chlorine (except a saltwater chlorine generator, SWG) for every 10 ppm FC that is added, the result will be an increase in salt of 8 ppm when the chlorine gets consumed/used (since the chlorine becomes chloride). For sodium hypochlorite and lithium hypochlorite, there is an additional 8 ppm salt added upon addition so the net result is an increase of around 17 ppm salt (not 16, due to rounding and other by-products). For Cal-Hypo, the extra salt added is around 2-4 ppm so the net salt increase is around 10-12 ppm.

CYA .. Min FC3 .. Target FC .. Yel/Mstrd Min .. Shock FC .. Yel/MstrdShock
0 ....... 0.071 ....... 0.111 ......... 0.151 .............. 0.641 ....... 1.501
10 ...... 0.81 ........ 1.21 ........... 1.61 ............... 4.5 ......... 7.1
20 ...... 1.51 ........ 2.4 ............ 3.1 ................ 8.3 ........ 12.7
30 ...... 2.2 ......... 3.5 ............ 4.6 ............... 12.2 ........ 18.2
40 ...... 2.9 ......... 4.6 ............ 6.1 ............... 16.0 ........ 23.8
50 ...... 3.7 ......... 5.7 ............ 7.5 ............... 19.8 ........ 29.42
60 ...... 4.4 ......... 6.8 ............ 9.0 ............... 23.7 ........ 34.92
70 ...... 5.1 ......... 8.0 ........... 10.5 .............. 27.52 …...... 40.52
80 ...... 5.8 ......... 9.1 ........... 12.0 .............. 31.42 ........ 46.12
90 ...... 6.6 ........ 10.2 ........... 13.5 .............. 35.22 ........ 51.72
100 ..... 7.3 ........ 11.4 .......... 14.9 ............... 39.12 ........ 57.32
120 ..... 8.7 ........ 13.6 .......... 17.9 ............... 46.72 ........ 68.42

1A minimum FC level is needed as a "reserve" for usage so in practice at least 2 ppm FC is required even at low CYA levels. The table above shows the amount needed for disinfecting chlorine for equivalent killing power (rates), but does not take into account the amount needed in reserve to prevent getting used up as this varies by pool.

2The shock levels shown have equivalent disinfecting chlorine amounts (in a column) but at high CYA levels it may be impractical to use such high FC levels. A partial drain/refill to lower the CYA level is usually what is needed or one can shock at a lower level but will take longer to kill the algae.

3Most saltwater chlorine generator (SWG) pools appear to prevent algae at a minimum FC level of 4.5% of the CYA level as compared with the roughly 7.5% of the CYA level shown in the "Min FC" column for manually dosed pools.

NOTE: A reasonable approximation to the above table is the following:
.... "Min FC" is 7.5% of the CYA level
.... "Target FC" is 11.5% of the CYA level
.... "Yel/Mstrd Min" is 15% of the CYA level
.... "Shock FC" is 40% of the CYA level
.... "Yel/MstrdShock" is 60% of the CYA level.
Since chlorine is more effective at lower pH, it is normally recommended to lower the pH before shocking at a high FC level, especially for yellow/mustard algae where lowering the pH to 7.2 before shocking at the above levels is best (and remember that the pH test will not be valid during shocking due to high FC levels).


Pool Size is 21,470

FC level target is 3 PPM at 3 PM (1 Qt. = 2 PPM using 12.5) at 30 CYA

PH level target is 7.3 (1 Qt Muriatic Acid lowers PH by .2)

TA target is 80 to 120

CA target is 200 to 400

CYA target is 30 to 80

Borate level target is 50 (1 lb. Boric Acid raises Borate by 1, 25 Oz. 20 Mule team Borax raises Borate 1)

Pool School recommended as below:
Plaster with Bleach
FC 3-7
pH 7.5-7.8
TA 70-90+
CH 250-350
CYA 30-50


The following chart shows how much the CYA, CH and Salt would rise after 6 months if there were 2 ppm FC per day chlorine usage and no water dilution:

........................ CYA ... CH ... Salt
Trichlor .......... 220 ...... 0 .... 295
Dichlor ........... 325 ...... 0 .... 295
Cal-Hypo .......... 0 .... 255 ... 360
Bleach* ............. 0 ........ 0 ... 595

*Bleach, chlorinating liquid, lithium hypochlorite and chlorine gas all result in no CYA, no CH and the same amount of salt.

Note that a rise in CYA of 220 ppm is much worse than a rise in CH of 255 ppm which is worse than a rise in salt of 595 ppm.


My 21,470 gallon pool costs me just under $ 500.00 in Chlorine and Muriatic acid per year. This is with a target CYA of 40-50. My TA hover around 90-110, and my PH is always rising so I target the low end of the range at 7.2 and add Muriatic acid when it hits 7.8 because I do not like to mess with Muriatic Acid on a daily basis. I like to get my Chlorine at the local pool store in refillable jugs and keep 8 of them for the summer usage so I do not have to go to the store as often. (It gets expensive here in July and August but not so much in January and February) I test my CL level just before sunset and add CL then so it will have all night to do it job before the evil orb has its way with it.

Have faith, it’s just a pool and if you stare at the chemical aspect of it long enough it will make sense.

 

[chem geek]

My 21,470 gallon pool costs me just under $ 500.00 in Chlorine and Muriatic acid per year. This is with a target CYA of 40-50. My TA hover around 90-110, and my PH is always rising so I target the low end of the range at 7.2 and add Muriatic acid when it hits 7.8 because I do not like to mess with Muriatic Acid on a daily basis.

If you are regularly adding acid, then your TA should be dropping unless you've got a lot of evaporation/refill with high TA fill water or you are adding some chemical to increase TA (such as baking soda). You should let your TA drop lower, to 70 ppm or perhaps somewhat lower, to see if your pH is more stable. Also in Arizona, if your pool is in full sun all day long you might do better with a higher CYA level and associated FC target as that should lose less chlorine per day.

 

[It's pooler in AZ]

You are correct. A CYA of 80 would save me money in chlorine cost, but when the dreaded Yellow Mustard comes to visit I would have no option but to by an algaecide to combat it. So my money saved would be spent on algaecide. To me BBB is about keeping it simple. With my test kit reading FC at 30 accurately is nearly impossible with a 12.5/100 dilution, so why give myself the headache for $100 to $200 a year savings possibility.

My pool evaporates at a rate of about 1.3 times a year and the fill water has a TA of 110 and PH of 7.8 in the summer. This combined with my plaster keeps my PH on the rise. Micro managing my TA is more work than it is worth with its natural range of 80 to 110 during the year, and my Muriatic Acid cost being only $ 70 dollars a year. That is of course as long as my Saturation Index is not out of line.

Thanks for the headache the other day. I was reading one of your past posts and now I know more about fecal matter than I ever wanted to know.
:-D

 

[chem geek]

Sounds like you've got a great understanding of the various trade-offs and are making the appropriate choices. It feels pretty good when one knows the pros/cons of different approaches and is able to find the sweet spot of cost, convenience and risk that works for them. The key is being properly informed.

I do my best with the headache-inducing posts; helps my asprin sales.

 

[It's pooler in AZ]

Thank You Chem Geek, your contribution of knowledge is truly appreciated.