Post Pool Store Problem with Chlorine level

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Pghpool

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Jun 22, 2015
5
Pittsburgh, PA
New to the forum - Great information - I wish I had discovered this years ago!

Had a problem with stains on the vinyl liner and steps last year. Removed by treating worst areas with oxalic acid in a sock and a treatment with Metal Magic. Stains re-appeared this year on opening the pool (in-retrospect after adding baking soda and shocking the pool). Disappeared with a vitamin c tablet. Water tested no metals but added 4 bottles of Metal Magic per pool store recommendations. Followed direction on the bottle to the letter. Stains disappeared but filter clogging daily. Chlorine levels low (0.0 - 0.5 with strips) but waited the two weeks before shocking or adding much chlorine (was using 3" tablets then). On adding baking soda to get pH up over 7.0 the stains re-appeared. Still backwashing the filter every few days. Back to pool store and they said to add another 4 bottles of Metal Magic. Added and the stains again disappeared. Water has been crystal clear the whole time. Free Chlorine 0.0 and total chlorine 1.0 (per pool store). Added more tablets. Can't get any free chlorine level and changing the filter daily. Back to pool store and they say phosphorus level is high and that is why chlorine levels are low. Sold my wife something for phosphorus.

At this point I wise up and guess that the phosphorus has nothing to do with the low chlorine, guessing that the Metal Magic is binding the chlorine and that is why I'm going through chlorine and DE like crazy. Went internet searching and discovered this forum and re-affirmed my suspicions that baking soda bleach are better than the pool store bad information. Problem now is that I'm still going through Clorox bottles and DE like crazy. Water looks beautiful. TF test kit numbers - Chlorine levels good after addition but go to 0.5 by the next day. Total chlorine 1.0, pH 7.5, CYA 100, alkalinity 150. Free copper looks like 0 or <0.5. I'm buying so much bleach at Sam's that they must be wondering if I'm cleaning up a crime scene (Truth is I am - ripped off by bad pool story advice over the years.)
 
Welcome to TFP!!:handwave:

I'm going to guess you have something growing in the water. My first suggestion is to stop going to the pool store. Their only response it to sell you something whether it helps or hurts your pool.....they just don't know any better.

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. But, what can you do?? We base our pool care system on accurate testing and only adding what the pool needs, when it needs it. To do that you need your own accurate test kit. Order a TF100 and at least include the XL option. That will give you what you need while you are clearing the pool, and probably enough reagents for a couple of years normal use.

The only other real option for a test kit is a Taylor K-2006. Be careful comparing prices because the K-2006 comes in sizes, designated by a letter. The basic K-2006 has .75oz bottles. Yo need to get the K-2006-C to get the larger bottles that you want. Even then it is a little short on the reagent & powder for the FAS/DPD test.

I also have the SpeedStir and Sample Sizer. They speed testing and accuracy.

While you are waiting for your test kit you want to add a bottle of 8.25% bleach to the pool each day and do some reading in Pool School. Start with these:
ABCs of Water Chemistry
Recommended Pool Chemicals
How to Chlorinate Your Pool
 
Your reading
tc 1
ph 7.5
cya 100 (that is where the test stops)
ta 150

We need you to do an extended CYA test, mix your cya test like normal, dump half and add half tap water... pour in tube as usual, get reading and multiply by 2 EG: black dot disappears at 80 x 2 cya is 160..

your CYA is why you can not keep chlorine in your pool, you should be at 30 to 40 for your area...

someone else will need to help with metal stains, I am not good at that yet :)

You have come to the right place... So its not a supprise, you will probably need to empty 1/4 to 1/2 or more pool water, sorry for the bad news

- - - Updated - - -

Tim, in the last line, they have a tf100 :)
 
Congrats on the TF-100. The first step is to figure out your real cya number and reduce that by draining and filling. Your measurement of 100 is the upper limit of the test so your actual cya level may be much higher. You're going to need to do the diluted cya test to get a better measurement. Directions for that are in the extended test directions here (scroll down to the cya test):
Extended Test Kit Directions

Also your FC is not good. If your cya is "only" 100 (as I said it could actually be much higher) your FC level needs to never drop below the minimum of 7 and you should be targeting 12 for 100 cya. At your currents level of FC the algae is getting an invitation to grow and killing it is going to be a major ordeal with the high cya.

So, first step, do the extended cya test and post your results and people will jump in and help from there.

It helps to add "TF-100 Kit" in your signature so that people replying know at a glance that you've gotten a good test kit now.
 
swoopman said:
It helps to add "TF-100 Kit" in your signature so that people replying know at a glance that you've gotten a good test kit now.
Click to expand...
That's OK - make fun of me for missing it:whip:

To be honest with 100 CYA I would recommend at least a 33% water exchange to get the CYA down abd then test again. You are going to have to get that number down anyway, so don't bother with teh extended test yet. You say inground in your signature, but don't say vinyl or gunite. For vinyl lined pools leave at least one foot of water in the shallow end to keep from floating the liner and all pool owners are cautioned that in areas with a high water table lowering the water too much can “float” the pool out of the ground.
 
Im not sure if cowboycasey explained the dilution properly as per the extended directions. The pool water should be diluted by half with tap water before adding the r-0013 reagent. If you add the r-0013 and then dilute after you would lose half of the reagent.

Fill the mixing bottle to the lower mark with pool water.
Continue filling the mixing bottle to the upper mark with tap water.
Shake briefly to mix.
Pour off half of the contents of the mixing bottle, so it is again filled to the lower mark.
Continue the test normally from step 3, but multiply the final result by two.

Notes
If you are not confident in your reading, you can pour the solution from the view tube back into the mixing bottle and then try filling the view tube again. You can repeat this portion of the test over and over again for several minutes without affecting the test results.
Click to expand...
 
Thanks for the speedy replies. My guess is that the CYA reading of 100 is on the high side as the test from the dreaded pool store was 70 and it was testing less than 100 on strips but I will do the extended test tonight. I was anticipating needing to do some water changes but was hoping that I wouldn't have to. I had thought that high CYA made less effective but not short lived? What is the knowledge/experience with my guess that it is the Metal Magic binding the chlorine and precipitating it out? There is a recurring dusting on the pool floor that I'm sweeping and I'm clogging my filter like crazy. Water is crystal clear so I don't think I have an algae or bacteria bloom going on (yet).
 
Metal Magic does not bind chlorine. It is an HEDP-based metal sequestrant and these are slowly oxidized by chlorine, but it's slow. If you had used an EDTA-based metal sequestrant, then a higher chlorine demand might be seen since that breaks down more quickly, but with HEDP it would be too slow to be seen as extreme on a daily basis.

The normal recommended dose for light staining or low metal content is 1 quart per 10,000 gallons. The most extreme they recommend is 4 times that. You estimate that your pool is 35,000 gallons and that you added 8 bottles which would be in between these. You might see a higher than normal chlorine demand because of this, but it wouldn't use up chlorine that quickly. More likely is that your FC dropped below that needed to prevent algae growth AND the HEDP that broke down from chlorine released phosphates in the water that let the algae grow faster. However, the algae would have been killed faster than it could grow if you had the proper FC level for our CYA level, but you didn't.

The proper prescription is to lower your CYA level by water dilution. After that, you should be able to maintain an FC level that prevents algae growth regardless of algae nutrient (phosphate, nitrate) level.
 
poolnoob.ca said:
Im not sure if cowboycasey explained the dilution properly as per the extended directions. The pool water should be diluted by half with tap water before adding the r-0013 reagent. If you add the r-0013 and then dilute after you would lose half of the reagent.
Click to expand...

Thank you for that, I knew I should have found the correct directions.. Sorry
 

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Pghpool said:
......... Chlorine levels low (0.0 - 0.5 with strips) but waited the two weeks before shocking or adding much chlorine (was using 3" tablets then).........
Click to expand...

Pghpool said:
I'll start the water exchanges tonight. Could I have that much of an algae problem without seeing it anywhere? The pool really looks great and what I'm brushing is really almost all on the bottom. Thanks again for the help.
Click to expand...
If you let your chlorine go to zero (or under your min per CYA level) over the course of two weeks I'll bet that the "stuff" you are brushing off the bottom is Algae.

Dom
 
When you do the diluted cya test you need to multiply the result by 2 so your cya was 160 and is now 120. You're right to keep up with the drain and fill.

Please update your signature to include your pool info as it really helps people when responding. For example, your target cya would be different whether you have a SWG or not and that would be info you include in your signature. Thanks.
 
Thanks again for the replies. Swoopman, I did the multiplications on the dilution CYA test so the 80 And then 60 after the first drain/refill were correct. Did another 7 inch drain/refill and the CYA is now a bit less than 50 and all is well. Holding FC levels of 5 without problems. Thanks.
 
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