New to home testing - big discrepancies between my results and pool store

linzi618

Active member
May 11, 2017
42
Pflugerville, TX
Hi all, new to this. 20K gal gunite pool in Central TX. Built in 2017

We’ve always had our water tested at L’s (can I mention names? We all know them...). We’ve always followed their maintenance recommendations and 80% of our tests are within “optimal” range. We have consistently had a variety of differing recommendations regarding our calcium and CYA levels. We’ve emptied 30% of our pool in the past to drop CH and it supposedly fixed it for a while. Gearing up for this season and we are having an issue with what I believe to be mustard algae on our walls. We also have a lot of scaling on our pool wall limestone and tile waterline. I’ve decided to take over testing and have done now twice, last night and this afternoon, with one L’s water test done to see discrepancies. Both of my tests came out about the same (18 hours apart). If you don’t mind, here are the levels (Pool Store (PS) vs. Mine)

PS - Mine
FC 3 2
TC 3 2.5
ph 7.6 7.8+
TA 84 140
CH 300 725
CYA 110 >100

Some levels are close but some are WAY off, which I’d like to learn if it is due to my newness to home testing or if the Pool Store (which i read everywhere not to rely on) is that far off. The pool math calculator app definitely tells me my levels will leave me prone to scaling, which is obviously happening. My water is crystal clear but i have that yellow/greenish slight growth on my walls which is pretty easy to brush away, but it keep returning. I’ve been brushing daily (5+ times a week) and we run our Polaris almost constantly.

I have the TF-100 test kit and follow directions exactly. Pool water was collected in same spot, 12 inches below surface in deep end of pool for all three tests done in the 18 hr span. I guess my main first question is the biggest adjustment that may need to be made....do I trust my newb reading on CH and start draining my pool (40% suggested by app)? I’m just scratching my head/doubting myself as to how the two sets of readings for TA and CH can be SO far off from each other.

Thank you for helping this newbie!
 

tim5055

Mod Squad
TFP Expert
LifeTime Supporter
May 11, 2014
10,892
Franklin, NC
OK, lets define the roles here....

Your role, to maintain a safe clean pool for the least amount of money as possible

That "L" place, their role is to separate you from as much of your money as they can. You know their managers get paid a bonus on sales volume in the store, right??

Not much credence is given to pool store testing around here. While you would think that a "professional" would be the best, unfortunately in most cases it is quite the opposite. Between employees who blindly trust the word of chemical sales representatives and high school kids working in the pool store for the summer you end up with poor results from their testing. Plus, the results of their "testing" is used to convince you that you need to buy things. Why do you think that testing is free?
 

linzi618

Active member
May 11, 2017
42
Pflugerville, TX
OK, lets define the roles here....

Your role, to maintain a safe clean pool for the least amount of money as possible

That "L" place, their role is to separate you from as much of your money as they can. You know their managers get paid a bonus on sales volume in the store, right??

Not much credence is given to pool store testing around here. While you would think that a "professional" would be the best, unfortunately in most cases it is quite the opposite. Between employees who blindly trust the word of chemical sales representatives and high school kids working in the pool store for the summer you end up with poor results from their testing. Plus, the results of their "testing" is used to convince you that you need to buy things. Why do you think that testing is free?
I totally share the sentiment which is why I’ve decided to take over testing myself! Where I’ve tapped the brakes is where I’m at right now with L’s telling me things look pretty great but my app calculator is telling me to drain half my pool lol! I’m running repeated tests to bolster my own confidence and I’m feeling pretty good that I’m performing the tests accurately. My main alarm bells are the high CYA (>100), TC 2.5 (obv not high enough in presence of high CYA, which I’m assuming explains the slight amounts of algae growth). And the presence of the calcium scaling I have around my tile line in my spa, the buildup of calcium in the grout lines of my pool waterline tile, and the white scale buildup surrounding my spillover waterfall from spa to pool has me believing my calcium hardness is way higher than L’s is reporting (their 300 to my 700). And alkalinity—-their 84 to my 130-140.

The 40% pool drain commences tomorrow morning!
 

tim5055

Mod Squad
TFP Expert
LifeTime Supporter
May 11, 2014
10,892
Franklin, NC
When you get your CYA down to a reasonable level, it's time to SLAM your pool.

Many in the pool industry feel it is normal to have a "little" or as you put it "slight amounts of algae". We are different. No amount of algae is ever acceptable. We eradicate it and than maintain sufficient FC as a ratio to CYA and it will stay away.

 

JJ_Tex

Bronze Supporter
Jul 17, 2019
1,144
Prosper, TX (DFW)
Welcome and sounds like you are heading down the right track. I'm sure Leslies will be disapointed they dont get to sell you algecide or several rounds of magic potions. Their recommendation to drain the 40% of your water to lower CYA would come several hundred dollars later :)

I'm not sure about the "filter" part of your signature, but generally Nature2 is a cartridge that introduces minerals/metals that are not recommended long term, and your filter is separate and usually a cartridge, DE, or sand filter. You should look at ditching the Nature2, but that is secondary to your water drain and SLAM, so focus on those first.
 
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Rancho Cost-a-Lotta

Silver Supporter
Apr 10, 2018
1,454
Rancho Cucamonga, CA
Your calcium level is high, but you can still achieve an acceptable CSI level with CH levels up to 850+. The calcium test is more dependent on proper agitation and testing methods than other tests. A Speedstir helps make this and other tests more accurate and more consistent. Make sure you used a 10 ml sample for the test as opposed to a 25 ml sample. That aside, as others have mentioned, trust your results. You could visit the Pool $tore on three different days and receive completely different results.

One thing to consider in determining the amount of water to exchange is the CH of you fill water. Use pool math to determine the correct volume based on target, current, and fill water levels. Shoot for the lower recommended CH range to delay future water exchanges. Since you won't be using CYA-laden trichlor anymore (right?), your future drain/refills will be based on calcium levels.

Here is some info on water draining/exchanges:
 

proavia

LifeTime Supporter
TFP Guide
Feb 6, 2015
1,860
Chandler AZ
You may wish to test your fill water also. Just test the pH, TA and CH of your fill water. If your fill water is high in CH, you may wish to consider a larger water exchange than 40%. Post up those results here and we can better advise you.

You list a Nature2 Fusion in your signature. Is that a Fusion Soft (Swg + minerals) or just a Fusion (chlorine tabs + minerals)? Consider removing the mineral cartridge from the unit as it adds metals to the water and can cause stains on the plaster.

Since you are using the PoolMath app, you can use it to log your results and also share them here thru the app. If you choose to post them here instead, please use the following format.... no need to list TC - we want to see CC instead.

FC
CC
pH
TA
CH
CYA
Water Temp

Since you have visible algae, you will need to SLAM Process . Stock up on liquid chlorine.
 

linzi618

Active member
May 11, 2017
42
Pflugerville, TX
Your calcium level is high, but you can still achieve an acceptable CSI level with CH levels up to 850+. The calcium test is more dependent on proper agitation and testing methods than other tests. A Speedstir helps make this and other tests more accurate and more consistent. Make sure you used a 10 ml sample for the test as opposed to a 25 ml sample. That aside, as others have mentioned, trust your results. You could visit the Pool $tore on three different days and receive completely different results.

One thing to consider in determining the amount of water to exchange is the CH of you fill water. Use pool math to determine the correct volume based on target, current, and fill water levels. Shoot for the lower recommended CH range to delay future water exchanges. Since you won't be using CYA-laden trichlor anymore (right?), your future drain/refills will be based on calcium levels.

Here is some info on water draining/exchanges:
I purchased a SpeedStir alongside my test kit and have used it with each test. My drain amount is based upon recommendation within the Pool Math app. The CH of my fill water (i collected my water from the same bib that fills my pool) is 200ppm, but the TA was higher than my pool currently (Fill water is 160, pool currently at 130).

Yes we currently use 3” tabs from Leslies in our chlorinator, so it is Tri-Chlor. Will need to research what we need to use instead to get a better control on the CYA. Leslies had us drain our pool ~30% last summer to drop the CYA. We were loading 5 tabs at a time into the chlorinator (set at 4) so unsurprisingly the cya was high. We’ve cut back to using a max of 3 at a time.

I did a lot of reading through the forums last night and what I believed to be calcium scaling may indeed be phosphorescence, but there is definitely waterline scaling in the spa. I could NOT get it removed last summer with pumice, but the buildup in the pool (at grout and mortar joints) we were able to chip off carefully with a putty knife and pumice. My pool is draining now and once we finish that I’m going to post a pic of the “scaling/phosphorescence” in question and post a pic for advice.
 

linzi618

Active member
May 11, 2017
42
Pflugerville, TX
You may wish to test your fill water also. Just test the pH, TA and CH of your fill water. If your fill water is high in CH, you may wish to consider a larger water exchange than 40%. Post up those results here and we can better advise you.

You list a Nature2 Fusion in your signature. Is that a Fusion Soft (Swg + minerals) or just a Fusion (chlorine tabs + minerals)? Consider removing the mineral cartridge from the unit as it adds metals to the water and can cause stains on the plaster.

Since you are using the PoolMath app, you can use it to log your results and also share them here thru the app. If you choose to post them here instead, please use the following format.... no need to list TC - we want to see CC instead.

FC
CC
pH
TA
CH
CYA
Water Temp

Since you have visible algae, you will need to SLAM Process . Stock up on liquid chlorine.
Fusion (chlorine tabs + minerals). We (I guess stupidly?) just bought the mineral cartridge for the first time a couple of weeks ago in an attempt to help with the algae...our PB told us it was a “nice to have” but not necessary so we never used it at the beginning. I guess lesson learned. As of the last Leslie‘s test we didn’t have any trace of copper in the water but the cartridge is brand new. And it was a pool store test, so... ??‍♀

I tested my fill water last night...CH is 200ppm so not bad.

Definitely planning to SLAM once we refill. Need this process done by the time it gets REALLY hot here. I guess a silver lining of the COVID quarantine is I have a load of time to obsess on this process...
 
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Rancho Cost-a-Lotta

Silver Supporter
Apr 10, 2018
1,454
Rancho Cucamonga, CA
The CH of my fill water (i collected my water from the same bib that fills my pool) is 200ppm
A 40% drain should bring your CH down to about 500 ppm.

Read up on CSI to learn how to mitigate scaling. Also below, some good info on waterline scaling.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
29,330
Laughlin, NV
With your elevated CH fill water, as you add water to the pool due to evaporation, your CH will climb.

Best to replace far more than 40%. But up to you.
 
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linzi618

Active member
May 11, 2017
42
Pflugerville, TX
A 40% drain should bring your CH down to about 500 ppm.

Read up on CSI to learn how to mitigate scaling. Also below, some good info on waterline scaling.
I’ll definitely read this info. Here are a few pics of scaling and phosphorescence in my pool. My main concern is if it is possible to remove the phosphorescence from the natural stone around my spa spillover. I don’t think it is advisable to use muriatic acid on natural stone, correct? I’m pretty certain the evaporation line on all the pool tile is calcium scaling, and the stuff accumulating in the mortar above the tile line and surrounding the spillover is phosphorescence, correct?
 

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Rancho Cost-a-Lotta

Silver Supporter
Apr 10, 2018
1,454
Rancho Cucamonga, CA
Here is my experience with scale removal. Matt (@JoyfulNoise ) provides some great info.