Calcium hardness: Which results are correct?

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jay42k

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LifeTime Supporter
Jul 20, 2011
9
Houston, TX
I have been using TF100 for two years. Recently, my Calcium Hardness has crept up to 430ppm. I took a sample to two different Leslies and Warehouse Pool Supply stores (four stores total). All have given me values in the mid 200's.

Confused, I ordered fresh TF100 test chemicals, followed the procedure exactly, and continue to come up in the 430ppm range with TF100. I took another sample to one of the Leslies today, and they came up with 220ppm.

I don't know what to think. It is hard to refute the preponderance of results from the pool stores; however, I also know from this forum that pool stores are notoriously inaccurate!

Is there a way to home-make a "standard" solution to test against my TF100? Something like add Calcium Hardness increaser to distilled water in a known quantity, dissolve it, and then run it on TF100? If so, what ratio would I use.

Please help! Thanks,
Jay
 
Generally you are best off trusting your own testing ... seems repeatable to me. Do you have the Speedstir? It can help with the CH test especially.

What does your tap water test at?

There probably is a way to make a standard solution, but I do not know it.
 
If you are using a speedstir, I'd trust your readings first.

As an aside, it doesn't really matter if you get 430 or 425 or 450, the differences won't affect CSI that much. So use a 10 ml sample and make each drop count as 25. It saves R-0012, as well as you wrist, unless you have a speedstir, in which case your wrist won't care. Directions are in extended-test-kit-directions-t25081.html
 
Thanks to everyone for their input! I ordered the standard R-7063 as recommended. This is the 200ppm calcium hardness standard. Here are the results:

TF100 showed 200ppm right on the money! :goodjob:

Good news is I was not going insane on my testing. Bad news is I need to drain down the pool some to bring my hardness more in check.

Learning: POOL STORES DO NOT HAVE A CLUE. Do not trust their testing.
 
430ppm is really not high enough that you need to immediately drain water to lower it. Just keep the pH in range (< 7.8) and you should be fine. Richard320's CH is regularly over 1000ppm.
 
As jbliz said, 430 ppm CH is not something to knee-jerk drain for. Post the rest of your test numbers, especially: ph, TA, cya, salt levels (if you purposefully add it), and borates (if you purposefully raised them).

What pool surface type do you have? Better yet, put your pool and equipment details into your signature.
 
Current tests:
pH: 7.8
FC: 9
CC: 0
TA: 80
CH: 430
CYA: 60
Na+: 3100
Volume: 17k, including spa
Chlorine: Saltwater. Hayward T-CELL-15 generator
Surface: Pebbletec
Heater: Hayward H400
Pump: Hayward Northstar 2.4HP, 2 speed. Runs 24h on low speed.
Filter: Hayward cartridge.
Location: Houston, TX. Pool runs low 90's in summer.

Other: Tap water is 100ppm CH

Questions:
--At what pH does things go wrong with high Ca+? (and how will I know since I can't look in the pipes!)
--What is the trigger for draining down the pool and lowering Ca+?
 

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Nothing in your test results suggest you need to drain.

jay42k said:
-At what pH does things go wrong with high Ca+? (and how will I know since I can't look in the pipes!)
Click to expand...
It has to do with the "Calcite Saturation Index" (CSI) which is an index to determine risk of scaling which you can read about here: http://www.troublefreepool.com/pool-school/calcium_scaling CSI depends on many factors, So you can be high on some things, but that can be mitigated by keeping other things lower. In your case, your CH is just a little high, but your TA is good (fairly low) at 80 ppm...so it counteracts the slightly high CH. Right now, if your pool temp is 80F, then your CSI is +0.11 (CSI lower than -0.6 or higher than +0.6 should be addressed).

jay42k said:
-What is the trigger for draining down the pool and lowering Ca+?
Click to expand...
Answer is above...but basically CSI above +0.6 without the ability to keep ph and TA low enough.

How old is your pool?

Have you been using calcium hypochlorite (cal-hypo) to chlorinate?
 
linen said:
Right now, if your pool temp is 80F, then your CSI is +0.11 (CSI lower than -0.6 or higher than +0.6 should be addressed).
Click to expand...
I watch my CSI religiously when I test, using the online pool calculator from TFP's website. It has never exceed +0.6. This summer, it varied in the +0.25 to +0.5 range prior to adjusting pH. Once I added acid, it would bring CSI down to -0.1 or so
linen said:
How old is your pool?
Click to expand...
2 years
linen said:
Have you been using calcium hypochlorite (cal-hypo) to chlorinate?
Click to expand...
No. I use a SWG to generate chlorine.
 
Sounds like you have a good handle on it then :goodjob:

It maybe that your CH is slightly higher (again, it really isn't very high) from when your pool was built.

Since you have a swg, it is not a bad idea to run the csi a little lower (slightly negative) to prevent the cell from scaling. Also, you may want to consider 50 ppm borates if you regularly do have cell scaling. This doesn't happen to everyone, but if you see white flakes coming out of a return, that could be signs of scaling in your cell.
 
I wanted to second this. I went to Leslie's today my own CH reading shows that I am at 490 PPM while the guy tells me that I am sitting at 240. Anyway he was off on my FC and everything else... It is pointless to take your water there.

Sorry to high jack this one. But, what test is best for checking phosphate levels? Just the Taylor phophate test or the strips by Aquacheck? I am asking because I do not want to trust the Leslie's results. Also what is best way to treat phosphate? I ask because we have huge Agriculture here and the winds bring some fertilizer and more with them.

Also how accurate our the Aquacheck test strips for salt? I am reading 4700 from my own testing when the store was stating it is 3700.
 
It is generally recommended to ignore the phosphate level. It doesn't matter how much "algae food" is in the water if the chlorine level is kept high enough to prevent algae from living in it. Is there another effect that you're concerned about from the presence of phosphates?
 
I did not know. No I was mainly worried about the Algae. I have been told by the pool store people and others that one should keep the phosphate level down to avoid using up the chlorine too quickly specially if one uses SWG. That is why I was concerned. So to confirm again I should not worry about checking my phosphate levels ever?
 
Yep, ignore the phosphate level. Most folks here never test for it. Running your SWG (or adding bleach for those of us who don't choose to run an SWG) to keep the FC level where it needs to be based on CYA is the best and cheapest way to prevent algae.

Follow the guidelines for an SWG pool, and you'll be fine: pool-school/recommended_levels. Also see: pool-school/chlorine_cya_chart_shock for the recommended FC level based on CYA (look at the chart for SWG in this one, too).

Finally, if you want more on phosphates and their unimportance for trouble-free pools, use the search at the top of the page and type in "phosphate". There is a thread where JasonLion and chem geek got into some of the complexities if you're looking for the detailed reasoning on the subject. You can find it here: phosphates-1000-to-worry-or-not-to-worry-t41602.html.
 
Also how accurate our the Aquacheck test strips for salt?
Click to expand...
plus or minus 400 is a guideline on accuracy. Most people report slightly more accurate results, though.

Check the expiration date on them. There is some good anecdotal evidence that they get pretty erratic when they expire.
 
Thank you both. I will forget about phosphate then because I read the info. on the link and seems to make absolute sense.

The salt test has a expiry of 12/2014. I was wondering whether I should buy the Taylor salt test instead. Are people getting more accurate results with those?
 

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