Our public water the nastiest stuff on the planet

RMcGirr83

Gold Supporter
Nov 19, 2018
958
Tuscola, TX
Been testing my CH and it's almost as high as the empire state building is tall. Got our local water quality report and it's like reading greek. Calling @JoyfulNoise help me obiwan.
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Maybe I haven't been taking anything into account when doing the tests (like magnesium in the water). Any advice?
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
33,378
Laughlin, NV
TA of 130 and CH of 260. Just like my fill water!

But you get rain. So you should be able to control CH a bit better by using rain water as much as possible.

TA will just mean you manage pH more often with acid.
 

RMcGirr83

Gold Supporter
Nov 19, 2018
958
Tuscola, TX
LOL @ rain, we get a massive, on average, 24 inches per year. Rained last night as a matter of fact. A whole 1/16" of an inch. Pretty sure the evaporation rate is higher than what the rain will replace. Water isn't cheap either at $.011 per gallon. Would cost me ~$200 to replace 80% of my pool water.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
33,378
Laughlin, NV
Do you have a water softener? Using softened water for pool fill water helps control calcium build up.

I am planning to install one soon just for the pool.
 

RMcGirr83

Gold Supporter
Nov 19, 2018
958
Tuscola, TX
No we don't have a true water softener. We use a pelican device which doesn't allow the calcium to build up on appliances and such...doesn't use salt.

I don't know of any water softener that can satisfy a 20k gallon pool without it costing just a bit south of the pool itself.

The main point of my posting this was confusion if magnesium maybe interfering with the CH test. Not sure if it does or not or if I should even be concerned with the mag in the water.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
17,380
Tucson, AZ
I can’t really read those water reports on my phone, print is too small and fuzzy. But magnesium is only an issue if it’s many times higher than calcium. The Taylor test accounts for magnesium by using the R-0010 buffer to get rid of it.

As for water softeners, salt based units work better. I have a 54,000 grain water softener hooked up to my entire house and to the autofill line on my pool. My input CH is 180ppm average and the general hardness (GH) is a bit over 210ppm. It can more than adequately handle my 7-person household and my swimming pool. Adding the autofill line to the softener is the equivalent of adding an extra person-year in terms of water use to the household. My softener regenerates about every 4 days in the summer and well over a week to 10 days in the winter. The softener uses 6-8lba of salt per regen cycle to make the brine and about 25 gallons of water to do the backwashing and rinsing. The additional cost of the water was barely noticeable but the CH rise in my pool is zero. Tucson gets 10” of rain annually (averaged over 3 years) and >90” of evaporation. Water cost a lot here. But, my only regret is not adding the water softener sooner. Regenerative softeners are more economical here because the filtration based ones like Pelican sells wouldn’t last a year or two before needing replacement especially if a pool autofill is needed.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
33,378
Laughlin, NV
Actually a small water softener is all that is needed for just the pool. I suspect your evaporation rate is typically fairly low. Maybe 20-50 gallons per day, at most. Your CH equates to about 17gpg. So a 30000 grain water softener could process at least 1500 gallons of your water before regen.

The report shows magnesium at 24 ppm. It is not significant compared to the calcium hardness.
 

RMcGirr83

Gold Supporter
Nov 19, 2018
958
Tuscola, TX
The report shows magnesium at 24 ppm. It is not significant compared to the calcium hardness.
Even though calcium is stated as 65.6 ppm?

For Joyfulnoise, maybe this will help
AverageMinMax
ALK128111162
Calcium65.648.597.3
Magnesium24.314.443.2
Hardness264184421

One thing I do miss about CT is how awesome our well water was (not to mention relatively free).
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
17,380
Tucson, AZ
Your CH as measured in units of calcium carbonate (CaCO3) is 164ppm and your Magnesium hardness as measured in units of CaCO3 is 100ppm. Your total hardness is 264ppm. Your CH:MH ratio is 1.6:1 which is pretty far off for terrestrial water (normally is closer to 4:1 to 6:1). The water is likely coming from a source on contact with a lot of granite to get that much magnesium.

If you test your tap water CH, before the softener, you should be getting a value close to 160ppm CH.
 

RMcGirr83

Gold Supporter
Nov 19, 2018
958
Tuscola, TX
For my own edification can you tell me how you came up with the PPM ratios please?

Just tested it directly from the main and it was 170 so close enough. As far as testing the pool water I assume that I can use the same ratio to come to the actual CH? Pool auto fill is fed directly from the main so by passes the softener.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
17,380
Tucson, AZ
So the thing to understand about ground water/drinking water testing is that municipal facilities are required to test for A LOT of different chemical species and while there are quantitative chemistry tests that can get them the answers, training people to do those tests would be a nightmare. So they almost always rely on mass spectroscopy as a testing method because the output of those machines is the exact concentrations of almost any atomic species including some organic molecules. Those tests will generate concentrations for the exact atom in question. So if you look at the data where the mass of magnesium is located (24.305 amu), you will get the concentration of magnesium atoms in mg/L or ppm. Same is true for calcium (40.08 amu) or any other element.

When testing for calcium using the wet chemical tests like the titration test in the Taylor kit, all of the reagents are based upon a standard chemical. You simply choose the standard basis that makes the most sense for the test. For calcium hardness, all of the reagents are standardized against a solution with a known concentration of calcium carbonate (CaCO3). So, when you are titrating with the R-0012 drops, every drop of the reagent will chelate exactly 25ppm worth of calcium carbonate in a 25mL water sample. So no matter what is in the water sample (eg, calcium only, or calcium and magnesium), the answer you get from doing the titration is always reported in units of CaCO3 or, as chemists like to say, equivalents. Now in the CH test, the protocol is designed so that only calcium is affecting the color change of the reagent and so then you are assured that you are measuring calcium hardness alone.

Now we go to the mind-numbing details of chemistry. One of the most consequential discoveries of chemistry is this - no matter what the chemical species is, a "mole" (written, mol) of any substance contains the same number of individual atoms or molecules as any other substance, that is, Avogadro's Number (NA = 6.023 x 1023 atoms/mol). It's related to the physical theory of the "conservation of mass" - in any chemical reaction, the masses of the substances involved never change, they simply get rearranged. Because of of this fact, one can relate quantities of substance in any chemical reaction to one another very easily. If you have 1 mol of calcium, it weighs 40.1 grams. If you have one mol of magnesium, it weighs 24.3 grams. These physical properties NEVER change.

So why does that matter?

Because now you can take the information you have about the measured amount of calcium in your water as Ca atoms and convert that easily to what that would be if it were measured as calcium carbonate. In other words -

65.6ppm [Ca] = 65.6 mg/L [Ca] * (100.1 gm/mol [CaCO3]) / (40.1 gm/mol [Ca]) = 65.6 *(100.1/40.1) = 65.6 * 2.496 = 163.7 mg/L [CaCO3] = ~ 164ppm [CaCO3]

The same can be done when converting magnesium ions into the effective magnesium hardness in equivalents of calcium carbonate -

24.3 x (100.1/24.3) = ~100 mg/L [CaCO3]

TH = CH +MH = 264ppm

A simple analogy would be to consider what is being done here like driving over a bridge from the US to Canada - your velocity doesn't change but you can either read your speedometer in units of miles per hour or kilometers per hour.

As far as the autofill goes, your pool water will be more concentrated with calcium than your tap water because the water evaporates and leaves the calcium behind. So unless you get very significant rainfall that overflows the pool, the CH will always increase.