Calcium Level Recommendations

[bwillick2015]

Hello All, First time poster here at TFP. Also first year owning an inground pool approximately 18,000 gallons, it was just installed end of last year, fiberglass and will be SWG. I have had other smaller pools in the past off and on but never put in as much effort and research as I have this go around for chemistry and other pool items. So my question is mostly regarding Calcium levels and why such a dramatic difference from recommendations at TFP versus some other pool companys.

Recommendations from the TFP calculator for my pool with SWG
PH 7.6-7.8
TA 60 -80
Calcium 350-550
CYA 70-80
Chlorine based on the 5% relationship if CYA 80 then 4ppm chlorine

Two other pool companies online information
PH 7.4-7.6
TA 80-120
Calcium 200-400
CYA 30-50 (80 max)
Chlorine 3

So for ph and TA we have some minor variances but I would not consider them that huge of a difference, for chlorine and CYA their recommended would not be adequate for the 5% relationship but with their max CYA value there is room to make that work.

I am just curious why such a large difference in Calcium recommendation?
Anyone with a fiberglass pool and SWG what do you run your numbers at? I live in southwestern Ontario Canada if that plays into anything for weather wise.

Thanks for any input

 

[mknauss]

Welcome to the forum!
CH is the tough one for fiberglass pools. If you do NOT have a heater or waterline tile with cement based grout, then the CH can be much lower. Some CH is needed to keep from cobalt staining. But not much. So 'guidelines' are hard to publish for our pool types.
You can see my PoolMath data if you click on my membername.
I suggest you read through Pool Care Basics - Trouble Free Pool and even look at a few of our videos TFP-TV - Trouble Free Pool

 

[JoyfulNoise]

The recommended levels are designed to keep the saturation index in a reasonable range. Too negative (corrosive) or too positive (scaling) are not good long term. Since TFP levels attempt to keep CO2 out gassing (and the subsequent pH rise) to a minimum, it was decided to use lower levels of TA. TA and pH both affect saturation indices and so small changes in those values lead to bigger changes in CSI. If one wants to maintain lower TA values to keep pH in check, then you need higher CH levels or else you’ll drive the saturation too far into the negative range. For SWGs, you want to ensure that your CSI is slightly negative at all times to avoid scaling inside the cell. So having low TA helps with that.

CH is very hard to adjust. The only way to lower it practically is through water exchange and all water tends to concentrate minerals. So CH can be a constant battle for some pools. Setting it once and leaving it alone makes pool care much easier.

 

[bwillick2015]

Hey guys thanks for both your quick replies.

mknauss I actually do in fact have a gas heater for the pool to help extend my season a little longer being in the north, but I don't have any water line tile. I did have a quick peak at your poolmath log, I beleive is what you were referring too but was unsure what numbers are you shooting at for each thing?
I actually have read a bunch of those pages in the pool care basics sections but I still have acouple more to do. ABC's of, recommended levels, FC to CYA rela, recomed chems, non recomend chems, pool circulation, test kits but i think still have 2 or 3 to read.

Right now my pool water was just fresh water that was put in end of last year. So far I have started to balance everything up to the point of Salt then Chlorine levels. For testing I have a taylor 2005 kit and I know I read many recommend the 2006C for the Fast/DPD test, and based on what I read on the page I can just order the extra stuff from TFTestkits that would turn mine into a 2006 kit.

Before I started adding anything ( i didnt really test past the calcium phase since I haven't added any salt or chlorine I would expect it to be zero, or nearly zero for chlorine based on whatever local water company sets their level to for drinking water.)
TA- 70ppm
PH- 8.0 to 8.1
Calcium -70 to 80ppm

Prior to reading TFP site information. Initially when I started balancing the documentation I read, was that since I needed to reduce my PH I should first increase my TA as the PH reducer would bring them both down, so I did that but after adding PH reducer TA never changed at all. As of last night I have left things at this point before adding anymore calcium increase. Products used were Bioguard balance Pak100 for TA increase, Bioguard lo 'n slo ph down, bioguard balance pak 300 calcium increaser

TA- 120ppm -
PH- 7.6
Calcium- 220ppm

If the recommended levels for Calcium are much higher ie 350 and that seems to work the best I have no problem bring it up to those levels just was curious before I went any further on the why. I didnt see anything when I read the chemistry ABC's but thought I'd ask is there anything that will disrupt the Calcium levels, ie should I shoot for a different number until I get the salt and the chlorine in?

And just to put this out there when reading the process before of balancing the pool (prior to coming to TSP site) it was indicated to me to balance TA >PH > Calcium > Salt > Chlorine > CYA and then I believe borate was an optional thing.

 

[mknauss]

For your situation, a CH of 250 ppm is more than enough. As Matt said, the levels were created to keep the saturation index in the normal range. For a fiberglass pool, the low end of the saturation index is not as big a threat as the high end, which can create scale.
CH will not be effected by salt or chlorine levels.
Your TA should balance at a reasonable level if the pH is in the 7's. The pH can rise if your fill water due to evaporation has significant TA. You likely get rain so I suspect will use little fill water due to evaporation.

 

[bwillick2015]

Ok thanks for the help from both of you. I haven't tested my tap water but thats all that was used to fill the pool last year and then some rain and snow melt over the winter and TA tested at 70 to 80ppm before adding anything.

I do have the Talor watergram saturation index wheel, is it pretty accurate to use for keeping an eye on the Index level? I do know it can change with the pool temp so I will just have to keep an eye on that during the beginning and end of season if im not running my heater the water is cooler right now 66 or 68 deg F. I believe on the backside of the watergram it had recommended between -0.3 to 0.5 and based on what Matt said I want to shoot for more the 0.0 to -0.1 side of things

 

[mknauss]

is it pretty accurate to use for keeping an eye on the Index level?

You can use it. Here at TFP, we use CSI - CSI and LSI - Further Reading. It is calculated using PoolMath

Unless you have a SWCG, the range of CSI can go up to 0.6 for scaling. The low end is -0.6 for plaster pools.

 

[ErniesPool]

The recommended levels are designed to keep the saturation index in a reasonable range. Too negative (corrosive) or too positive (scaling) are not good long term. Since TFP levels attempt to keep CO2 out gassing (and the subsequent pH rise) to a minimum, it was decided to use lower levels of TA. TA and pH both affect saturation indices and so small changes in those values lead to bigger changes in CSI. If one wants to maintain lower TA values to keep pH in check, then you need higher CH levels or else you’ll drive the saturation too far into the negative range. For SWGs, you want to ensure that your CSI is slightly negative at all times to avoid scaling inside the cell. So having low TA helps with that.

CH is very hard to adjust. The only way to lower it practically is through water exchange and all water tends to concentrate minerals. So CH can be a constant battle for some pools. Setting it once and leaving it alone makes pool care much easier.

Thanks. Best explanation I have seen yet.