I am now confused.

[Earl42]

Here were my numbers on Tuesday:
FC 0.5
CC 1
TC 0.5
ph 7.2
T/A 160
CYA 90

So, the next day, I added 3 gallons of 6% bleach.
checked a few hours later:
FC 8

So I add 1/4 gallon more and go to bed.

I just now check
FC 1.5
CC 1
TC .5 ???? shouldn't FC and CC sum to TC?
ph still 7.2
CYA 100??? Did it twice, both monday and today, even had my wife do it once to verify.

My water is nice and clear.

I am about to add 3 more gallons of bleach.

I humbly plead to the lords of the pool. "What am I doing wrong?"

 

[Richard320]

Well.......What are you using to test the water?

If it's test strips, that's what you're doing wrong. If it's a drop test, you're not following directions somehow. The FC,TC, CC numbers make no sense, as you noted.

But that much bleach tells me that either a)you don't have anywhere near as much CYA as you think or b)you are on the verge of an algae bloom.

 

[Earl42]

TF-100 test kit

Should I be testing this pool side? I have just been taking a large glass out to the pool, putting it in mouth down and turning it up to get water from about 1 ft. down. I am then taking that in side and using it to do testing. I rinse and paper towel the cup out thoroughly after words.

Do I need to be in sunlight for the CYA test? I imagine more light would make it easier to see and thus give me a lower CYA reading.

 

[JasonLion]

Taking a water sample inside and doing your testing there is fine. But there are two times when sunlight helps, reading the PH test, and reading the CYA test. You can get a slightly higher than actual test result when doing the CYA test with indoor lighting.

I gather that when you are reporting TC you are using the OTO test, drops turn the sample various shades of yellow which are compared to a color chart? There are two comments about the OTO test, first give it 30 seconds for the color to develop, and second, when in doubt about levels trust the FAS-DPD test (powder turns the sample pink, and then drops eventually turn it clear again). But when testing for some chlorine or no chlorine at all, go by the OTO test.

Your CYA level is very very high, which is a problem. Worse, CYA levels over 100 will usually show up on the test as being 100. I suggest doing the test again, but this time mix equal amounts of pool water and tap water, do the CYA test with that, and multiply the result by two. That will tell us if CYA is around 100 or actually much higher.

You could actually have a low level algae problem and still have clear water, or you might have ammonia in the water. Regardless, sInce FC is falling so quickly you need to shock the pool. With CYA around 100, you need to bring FC up to about 30 to shock the pool. So far you have only been bringing FC up to 12 or so, which is fine when everything is going well, but not enough to solve problems.

 

[Earl42]

When I did the modified CYA test I came up with 120
I am thinking I need to do some water replacement. Is that a wiser choice then trying to chlorinate at such a high CYA?

 

[JasonLion]

Yes, I strongly recommend replacing water to get CYA down to something more reasonable. Ideally you should aim for a CYA of around 60, but 80 will do.

 

[aa62579]

Lowering your CYA would be a wise choice. If not, looks like you need a FC of over 39 to shock, which would take around 11 gallons of 6% bleach to reach the first time and no telling how much more during the shock process.

 

[Earl42]

OK, perhaps a silly question, but what is the best way to drain water from the pool?

 

[JasonLion]

There are many different ways. If you have a bottom drain and can turn off the skimmers you can usually drain with the main pool pump. Of you can sometimes use a vacuum hose from a skimmer to drain from the skimmer with the main pump even when the water level goes down. Or if there is somewhere nearby that is lower than the pool you can use a garden hose to syphon water out. Or you can use a cover pump to pump the pool out, or rent a sump pump, and so on.

With a vinyl liner pool, you want to leave at least one foot of water in the shallow end to make sure the liner stays in place.

 

[Earl42]

OK, replaced a lot of water, brought the cya down to 80. Put enough chlorine in this morning to get from FC 0 to 31. Did that at about 11:30 am. We went to the lake with some friends so I could not test shortly after shocking to verify that 31. When I returned home FC was at 10.5 but CC was 0. Shocked again to 31, hoping it holds. One question, while I had the water down I opened and cleaned the cartridges. I now have a little bubbles coming out of the return nearest the pump/filter. Does this mean I have a small air leak somewhere? All of the 3 other returns are fine.

 

[JasonLion]

Did you remember to let the air out of the filter after you cleaned the cartridges and had the pump running again?

 

[Earl42]

I didn't know that I was supposed too. How does one do that?

 

[JasonLion]

Most filters have an air release valve at the top of the filer. Any time air might have gotten into the filter, certainly any time you have cleaned the cartridge, once the filter is back together and the pump is running you should open the small valve on top of the filter and leave it open until a steady stream of water comes out, then close the valve. Filters where a multi-port valve is mounted directly to the top of the filter do not need the air vented.

 

[Earl42]

Thanks I found it, fixed it right away. Pool is sucessfully shocked! Thanks for the help!

If I want the chlorine test to have larger resolution, I half the pool water with tap water and multiply my drops by 1? Is my math right?

 

[Richard320]

Thanks I found it, fixed it right away. Pool is sucessfully shocked! Thanks for the help!

If I want the chlorine test to have larger resolution, I half the pool water with tap water and multiply my drops by 1? Is my math right?

You're talking FAS-DPD, not the color block, right?

In theory, yes. In reality, no. For starters, tap water usually has some chlorine in it, and sometimes chloramines, which show up as CC. Secondly, each time you dilute, you increase the margin of error, and the difference between .1 ppm and .2 ppm resolution is going to be lost. Third, due to losses from sunlight, the water at the very top will have less FC than the water at the bottom of the pool. Not a lot, if you have good circulation, but enough to make the ultrafine resolution useless.

If you simply must know that precisely, use a 50 ml sample undiluted.

 

[JasonLion]

If you do measure FC with dilution, make sure to use chlorine free water. Most tap water has chlorine in it, which will mess up the results. If you mix equal parts of pool water and chlorine free water together and do the chlorine test on that you do indeed multiply the result by two. If you are doing the 10 ml FAS-DPD test, that is the same thing as multiplying the number of drops by 1, instead of by 0.5. That approach is reasonable when measuring very high FC levels.

 

[Earl42]

Jason, that is what I was thinking. I wanted to measure the shock level without using as mush 0871. I think I stated my question backwards. I wanted lower resolution or higher chlorine jump per drop. Sorry, I should have been more clear about what I wanted.