Calcium Hardness Sudden Change

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K

Ksbguy

Well-known member
Jul 8, 2022
46
Florida
Pool Size
14000
Surface
Plaster
Chlorine
Liquid Chlorine
Hello,

Plaster pool is 2 years old and I've maintained my CH at 350 checking monthly. In the rainy season CH was added to maintain as needed. CH hasn't been added in over 6 months and water used to fill pool is RO water with 25ppm CH. Maybe 200 gallons has been added in the last 6 months in addition to rain (more rain this year here)
I recently switched to new reagents from TF Test Kits and it's showing 500 instead of 350. The old reagents read 350 but they were maybe 8 months old. They've sent me an additional set of R10, R11L and R12 and also shows 500 so we don't think it's the reagents.

Range of chemicals pool is kept in tested daily to every other day. Pool has constant PH rise.

TA 50 - 70
PH 7.5 - 8
Borates 30 - 40ppm.
FC 4 - 5 (Liquid Chlorine)
CYA 40

What caused CH to jump?

Thanks!
 
There seems to be something wrong with either the old or the the new kits you have. Could be the drop tips giving wrong drop sizes , could be reagent concentration.

Common sense says the the two new kits are right. If you want an independent opinion which one is wrong, you can try an aquarium test kit, for example this one:

www.bulkreefsupply.com

RedSea Calcium Pro Test Kit

Why does BRS recommend this? Our favorite all around test kits are the red sea kits. With easy to follow directions, and consistent results, the Red Sea Calcium Pro test kit can always be found in our testing closet. The titration is made even easier with the included syringe holder that makes...
www.bulkreefsupply.com www.bulkreefsupply.com

I have used it myself, Taylor reagents can be a bit difficult to source down here sometimes. It's a bit more fiddly, using a syringe rather than counting drops.

Only thing you need to be aware of, is that the fish world measures calcium in units of mg Ca per litre, but in the pool world we use mg CaCO3 per litre (meaning the milligrams of Calcium Carbonate that have to be added to a litre of water to end up with that amount of Calcium).

All you need to do is to multiply the result from the aquarium kit with 2.5 to get "pool" units.
 
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Agreeing with mgtfp, it is logical to assume the two most recent reagent are correct.

Also, we know that calcium does not appear magically in a pool unless someone puts it there (maybe with fill water) so that sorta confirms the last two tests.

I can think of no reasonable answer to your CH "shooting up" like that so I think you can say it has always been there and disregard the earlier test.

A 500 CH is very manageable but 250-300 is perhaps better. The Florida rains may help to dilute it somewhat. Did we determine what the CH of the fill water is? If it's pretty low, it might be worth a partial drain of the 500 CH and refill with lower CH water.

I would probably just leave it alone at 500 for the time being.
 
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duraleigh said:
Agreeing with mgtfp, it is logical to assume the two most recent reagent are correct.

Also, we know that calcium does not appear magically in a pool unless someone puts it there (maybe with fill water) so that sorta confirms the last two tests.

I can think of no reasonable answer to your CH "shooting up" like that so I think you can say it has always been there and disregard the earlier test.

A 500 CH is very manageable but 250-300 is perhaps better. The Florida rains may help to dilute it somewhat. Did we determine what the CH of the fill water is? If it's pretty low, it might be worth a partial drain of the 500 CH and refill with lower CH water.

I would probably just leave it alone at 500 for the time being.
Click to expand...
Aside from rain water the fill water is 25ppm CH so marginal.
 
I have found dropper tips to be problematic in that a "drop" is merely an approximate (and variable) value. The accuracy of the requisite drops can, however, be verified by using a <$6 (US) 5ml graduated cylinder (Amazon) and checking to verify that there are indeed 25 drops per milliliter. Note: 25 drops per milliliter is a proprietary Taylor standard, not the pharmacological standard of 20 drops per milliliter. Obviously, if you aren't getting the properly metered amount of reagent per test, your results will be somewhat meaningless. (If the graduated cylinder is perfectly clean there is nothing wrong with pouring the "test" back into the reagent bottle, so no chemicals are lost.) Another point to be made is that all of the dropper tips are "measuring" tips except the one found on the R-0013 CYA test bottle. It is not designed to accurately measure (only to dispense) and is opaque white (instead of clear) to make sure the tips don't get mixed up.
 

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