Pool water looks a little bit like a snow globe....

[ejhutchens1]

So… temperatures in Tucson finally dropped enough that it became practical to drain all that high calcium hardness water out of my pool, and replace with fresh water. After finishing my initial chem treatment, my water numbers are now as follows (per my TF Pro test kit):

PH = 7.6
FC = 4.0
TC = 4.0
TA = 120
CH = 200
CYA = 75
SALT = 3400
TEMP = 70 F

I have questions about a couple of these numbers:

• I measured the TA number at 120 immediately after I refilled the pool with city water, before I added any treatment chems. I didn’t add any sodium bicarb during the treatment, and the TA never budged, remaining at 120. The TFP target for TA is shown as 70 --- how important is it bring this number down to target? Should I acidify & aerate to bring the TA number down? My pool has an in-floor cleaning system, so I don’t have any simple way to aerate.
  
  
• I measured the CH number at 175-200, which I see is somewhat low compared to the TFP recommended ranges. However, I’m a bit paranoid about calcium --- having just spent year of hard labor scrubbing scale off of waterline tiles & constantly netting out piles of calcium carbonate flakes. I tried using a test strip to measure CH, and the strip is indicating more like 300. I also tried using a “water hardness” test kit (Hach 5B) that was left with us a couple of months ago by our water softener installer, and it gave a result of 17 grains --- which I was told to multiply by 17.1 to convert to ~290 ppm. So, my question is --- should I try to correct this CH number upwards by adding calcium? My TF Pro test kit says my CH is low, but the 2 alternate tests say that I’m within the low end of acceptable range. I just changed my auto-leveler make-up water to softened water, so I don’t think CH should build-up as quickly as it did before. But I really don’t want a repeat of my previous high calcium issue, so my inclination is not to invite trouble by adding calcium….

Thanks for your help!

 

[mknauss]

Input your test data into PoolMath. See what the CSI is. I suspect leaving the TA as is will let you leave the CH as is. As long as CSI is near or above -0.3, no issues. When pH hits 8, lower it back to 7.6.

 

[wireform]

So… temperatures in Tucson finally dropped enough that it became practical to drain all that high calcium hardness water out of my pool, and replace with fresh water. After finishing my initial chem treatment, my water numbers are now as follows (per my TF Pro test kit):

PH = 7.6
FC = 4.0
TC = 4.0
TA = 120
CH = 200
CYA = 75
SALT = 3400
TEMP = 70 F

I have questions about a couple of these numbers:

• I measured the TA number at 120 immediately after I refilled the pool with city water, before I added any treatment chems. I didn’t add any sodium bicarb during the treatment, and the TA never budged, remaining at 120. The TFP target for TA is shown as 70 --- how important is it bring this number down to target? Should I acidify & aerate to bring the TA number down? My pool has an in-floor cleaning system, so I don’t have any simple way to aerate.
  
  
• I measured the CH number at 175-200, which I see is somewhat low compared to the TFP recommended ranges. However, I’m a bit paranoid about calcium --- having just spent year of hard labor scrubbing scale off of waterline tiles & constantly netting out piles of calcium carbonate flakes. I tried using a test strip to measure CH, and the strip is indicating more like 300. I also tried using a “water hardness” test kit (Hach 5B) that was left with us a couple of months ago by our water softener installer, and it gave a result of 17 grains --- which I was told to multiply by 17.1 to convert to ~290 ppm. So, my question is --- should I try to correct this CH number upwards by adding calcium? My TF Pro test kit says my CH is low, but the 2 alternate tests say that I’m within the low end of acceptable range. I just changed my auto-leveler make-up water to softened water, so I don’t think CH should build-up as quickly as it did before. But I really don’t want a repeat of my previous high calcium issue, so my inclination is not to invite trouble by adding calcium….

Thanks for your help!

Consider the cya 80 and target FC is 6. FC of 4 is minimum and can get you in trouble very fast. Try to run the FC hot atleast 8. The pool will feel the same and the equipment can handle that easily.

 

[ejhutchens1]

** MKnauss, I plugged my current numbers into PoolMath, and played around with them a bit. I'm thinking I may be forced to fight my 'calcium paranoia', and add at least a little bit of calcium chloride. I don't close the pool in the winter (we occasionally heat it for use it when we have visitors), and I've seen water temps get down into the low 50s before --- and PoolMath indicates that this lower water temp would drive my CSI down to around -0.5.

Just out of curiosity --- if I had no test kit and could only go by observing the pool, what "symptoms" would I begin to see if the CSI stayed too low? I've lived through high CSI and know what that looks like (flakes, scale, etc.), but I have no idea what a sustained low CSI condition would look like.

** Wireform, good thought --- I'll bring the FC up a bit more from where I am currently. I haven't re-installed my SWCG yet, but plan to do that later today. I've never had any issue with algae or anything else organic with this pool (maybe it's all the sunshine we get here plus the added Bioshield UV treatment?) so I'm hesitant to potentially shorten the lifespan of my SWCG by working it any harder than I really need to.... Thoughts?

I really appreciate the input & feedback. I think I've finally gotten the original high CH problem behind me now.

 

[mknauss]

I would not add calcium with your fill water. It takes a long time at low CSI for the plaster to be damaged. That is all the effect you will see. And it takes a very long time.

By early next year your CH will have risen. Evaporation occurs all winter, and you will be using fill water. Unless you have access to softened water, then use cal hypo for a while to chlorinate and then use softened water.

 

[ejhutchens1]

I now have a soft water supply going to my auto-fill, so I should no longer have any significant source of calcium going into my pool on a routine basis.

What would early signs of "plaster damage" look like in a pool with a plaster/pebble surface, how would I first recognize that I might have a low calcium issue? Would big chunks of the pebble surface just start flaking off, or would there be more subtle signs of problems that I might notice earlier? While I certainly don't want to get the pool back into a high calcium condition, I also don't want to ignore the fact that low calcium comes with its own issues, even though those issues may take some time to develop.

Also --- my TA is a bit high at 120 now --- do think it will just continue to hover near that level, or will it tend to drift up or down over time?

 

[mknauss]

You would start to see pebbles coming loose, etc.

If you are now using softened water, I would get your CH to 250+ ppm using cal hypo or if you wish, calcium carbonate.

Your TA will rise with fill water additions and lower with acid additions to reduce pH. Every pool tends to find its balance point. My pool has settled with a TA of around 100 ppm and I add acid every few days to a every week (depending on fill water additions). CH is pretty steady as I use softened water.

 

[reggiehammond]

Late in saying this but using acid on your SWCG reduces it’s useful life. Typical scale can be pushed off with a popsicle stick and stream of hose water. Acid rinse is last/last/last resort as it’s eating the rare earth metals that make the thing work…