Salt and CYA dropping, CH going way up

[cameradude]

Hey all,

This is my third summer with this pool and I have never seen this before. I live in AZ so we started swimming just after Easter, my pool chemistry was good. Then back in May I started getting a white dust in the pool. I don't have Jandy valves but in the skimmer basket there is a pipe from my main drain that was capped. I opened it and bought a diverter to start pulling from the main drain as well.

I left town for a few weeks and when I came back my salt had dropped from 3100 to 2800, my CYA dropped from 60 to 30 and my calcium hardness went from 350 to 490. Everything else was in the normal range. I figured there was a leak somehwere in that main drain pipe (which might have been why the PO had capped it) so I re-capped it. I put in 40lbs of salt so my SWG would work and a bit of CYA but I didn't want to load it up with chemicals in anticipation of having to do a partial drain to lower my CH.

Despite the additon of salt, over the next 2 weeks my salt dropped back down to 2800 and the CH went up to 670. I thought I still had a leak and as I was looking at the output pipe on my pump and there was a tiny trickle of water. That hardly seemed like enough of a leak to be effecting my chemistry so much but I removed the pipe and re-sealed it with Tplus2. Then to test for a leak I did the bucket test, I shut off my auto water filler on my pool and marked the level. Then I put a 5 gallon bucket filled mostly with water on my top step and marked that level. After 24 hours both the pool and the bucket lost the same amount of water, a little over 1/4 inch. So I thought I did not have a leak and my chemistry should stabilize.

I put in another 40 lbs of salt (raising me back up to 3000) but in the last 4 days I am back down to 2800 salt and my CH is at about 1000.

What gives?!

 

[Griswald]

How are you measuring?

What you describe is chemically impossible, so I'd bet on bad measurements.

 

[cameradude]

How are you measuring?

What you describe is chemically impossible, so I'd bet on bad measurements.

I test with my own kit and then take a sample to the pool store. Getting very similar readings from the 2 sources.

Why, what should be happening?

 

[proavia]

What test kit are you using?
How old are the reagents?
Are you holding the reagent bottle perfectly vertical and allowing the drops to fully form on the tip before they drop?
Are you swirling well between each drop?

Pool store testing is inconsistent at best. You need your own high quality test kit with fresh reagents. We recommend and use only the TF-100 or K2006C. Both use Taylor reagents - the TF-100 is the best bang for the buck as it contains more of the reagents you will need for the tests you do most often. Compare test kits here: Pool School - Test Kits Compared

Your CH results are suspect. It's impossible to go from 350 to 490 to over 1000 in a few weeks - unless you dumped in a bunch of calcium.

Please post a FULL set of current test results.
FC
CC
pH
TA
CH
CYA
Salt
Water temp

 

[cameradude]

FC 1.5
CC .5
pH 8.0
TA 80
CH 1000
CYA 30
Salt 2800
Water temp 90

For the record, my CH went from 390 to 1000 over the course of about 2.5 months. Still shockingly fast but not a few weeks.

I know a few of my numbers are off like CYA but I am anticipating having to drain the pool over this mess so I don't want to dump a bunch of money into the water before I pump it out. My ph is high even though I have been putting acid in it regulalry to help with the calcium dust on the bottom of my pool.

I sometimes take my water into the store just to provide another data point in case something goes screwy with my kits. I have a Taylor FAS-DPD chlorine test kit (about 6 months old) and a DPD test kit from Leslie's (a couple years old) that I use for everything else. My and their readings are almost always within 5% of each other.

I suppose some of my reagents could be old but wouldn't very similar readings from my kit and bringing the water into the store indicate at least ballpark accuracy? I dabble in statistical analysis and it seems very unlikely that separate testing methods would be inaccurate to the same degree across tests over the course of a several months.

 

[proavia]

We dont put much credence in pool store testing - even if it's close to your own testing. The couple year old reagents could be going bad too - even more so if they weren't stored inside the house (not the garage) when not in use.

If the test results are accurate - When plugging all your numbers into Pool Math it shows a CSI of 0.83. That's WAY too high and can cause calcium scaling. Based on the test results you provided, even lowering only the pH to 7.2 will drop the CSI to 0.05. The CSI range is +0.60 to -0.60 -- but keeping it within +0.30 to -0.30 is preferred. For high CH it's better to keep it slightly negative (so 0.00 to -0.30). Adjusting TA and/or adding CYA will adjust the CSI even lower.

I'm still leaning toward testing issues with CH - especially considering the wide range (350-1000) you reported over the course of a few weeks. Seriously consider replacing all of the reagents - or get yourself a new TF-100 and a Speedstir if you can swing it.

Your FC is too low for your CYA. And with a SWCG, your CYA is too low - I'd bet your FC burns off quickly. You're possibly on the verge of an algae outbreak - add some liquid bleach now to target an FC of 5-6 ppm and never let it get below 2 ppm. With only 30 ppm CYA, the sun's UV rays are going to burn off the FC quickly.

 

[cameradude]

Yup, I can swing a new test kit and a stirrer will make it fun! I will order from TFTestkits.

Given the white dust in my pool I feel like I can assume that my CH is too high and a partial drain is probably in order. I am going out of town again for 10 days but my kids will still want to use the pool while I am gone (its around 110 degrees here now). So I guess I will order the test kit, dump in some CYA and re-assess when I get back to town at the end of the month.

Does that sound like a good plan?

 

[proavia]

Good job on ordering the TF-100 and Speedstir! Ordering now will assure it's there on your return.

Yup - hovering around 110 for the next week. I'm just down the road in Chandler.

Is the "dust" loose where you can get some out? If so, after collecting some pour a little acid on it. If it fizzes, it's calcium.

Get the pH down to 7.2 in addition to adding CYA. In so doing, you can easily put off draining until after swim season - maybe longer. Let the kids enjoy swimming. Make sure the FC and pH aretested and adjusted while youre gone. When you return post a full set of test results with the new test kit and we can go from there.

 

[pooldv]

Salt, CYA and CH will all act the same in a pool. None evaporates, they only leave the pool when draining, overflowing or splash out. The only exception would be if you have a leak and an auto fill. Your fill water will have calcium but no CYA or CH. So, with a big leak your CYA and and salt could drop while CH rises.

 

[jblizzle]

What is the CH in your tap (refill) water?

I agree that most of what you are reporting is not really possible.

CH would only go up due to adding calcium or due to evaporation ... and that level of increase is not possible due to evaporation unless your tap water were nearly a solid

CYA and salt would only drop due to physically removing water.

Slightly correcting the above post, the CYA, salt, and CH might behave a little different from each other due to a leak. Because while the CYA is 0 in tap water, the salt and CH are not so they would not reduce as much as the CYA.

 

[cameradude]

What is the CH in your tap (refill) water?

I agree that most of what you are reporting is not really possible.

CH would only go up due to adding calcium or due to evaporation ... and that level of increase is not possible due to evaporation unless your tap water were nearly a solid

CYA and salt would only drop due to physically removing water.

Slightly correcting the above post, the CYA, salt, and CH might behave a little different from each other due to a leak. Because while the CYA is 0 in tap water, the salt and CH are not so they would not reduce as much as the CYA.

I measured my tap CH at 270.

I feel like my test with the bucket ruled out a big leak but my salt level has dropped again to 2700 which is down 100 since yesterday.

I put in 5lbs of CYA his morning, I am hoping this salt business is a fluke that will stabilize once I get everything else balanced.

 

[jblizzle]

How are you getting the salt levels? The number that the SWG reports can vary a good bit and will get lower as the cell scales up due to high CH and pH levels.

 

[cameradude]

How are you getting the salt levels? The number that the SWG reports can vary a good bit and will get lower as the cell scales up due to high CH and pH levels.

Great minds think alike!

I ran out of strips a while back and my cell was giving me almost exactly the same readings for the last year. I looked inside my cell about 15 minutes after I last posted and sho 'nuff it needed to be cleaned. My salt is at 3500!

I have been so preoccupied with the last month of legit salt drops and all the other stuff going on with the pool I overlooked one of the most obvious explanations of lower salt reading.

D'oh!