Strange test results - Why you should RTFM

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Vectrix150V

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Dec 9, 2013
31
Newcastle, NSW, Australia
OK - I'm an idiot.

Should have read - http://tftestkits.net/Test-Kit-Instructions-10.html rather than the instructions in the lid of the Taylor K2006 kit...

Backstory here - new-pool-owner-and-new-pool-newcastle-australia-t72200.html

Was battling a mustard algae problem, lots of chemicals added (tons of bleach, copper algaecides etc).

I've been testing with a Taylor K2006, using a 10ml sample, and err... 2 scoops of R-0870 (aagh!) as the FC has been pretty high - I read on the TFTestkit website the instructions are to use one scoop. Dang. No idea what that would have done to the results (falsely double them?).

I've also been having very high PH readings, which I have been adding muriatic acid, with the end result of a TA of just 30.

(Since read that PH readings are inaccurate at high chlorine levels)

So I used the poolmath calculator to fix the TA problem - 30 to 80 (5m long, 3.5m wide pool with a 1.52 average depth = 32,300 Litres) and it stated about 3Kg of buffer - I put in 2Kg, and ended up with 100ppm (??!) which isn't ideal for a SWG pool.

Strange.

Even weirder was the fact that the 45ppm CYA tested a few weeks ago now appears to be less than 30 (ie. could still see the black dot on the base when all the solution was added) - so added 1.5Kg cya - will test tonight.

PH tested at about 7.8 this morning, with FC at 17 (or 8.5 - not sure now).

I'll retest the chlorine tonight, and figure out whats going on here. A bit more acid should drop the TA.

Salt levels are also too high so I will probably drop some water out as well there.

Pool looks perfectly clear now, but getting this chemistry right... Hmmm.

CH is only 100 - is this an issue with a fibreglass pool? Seems pointless to increase it at the risk of scaling and having to remove deposits from the SWG cell.
 
Extra powder for the FAS-DPD chlorine test will not change the results at all. Too much powder is not a problem; not enough powder can be, especially when your FC is high.

Note that the instruction booklet that comes with the K2006 has more detailed information about the tests and about interactions, too.

You can leave your TA alone and let it drift down as you correct the pH. There's no hurry to correct a TA of 100.
 
Also you won't get an accurate PH test with FC levels of 10 or above. It will read a false high. You said your FC was 17 when you tested PH this AM.
For your SWG you want your CYA level to be 70-80 ppm.
 
Your CH level is not a real problem short term. Long term you'll want to get it up to the recommended levels. This will help prevent iron staining and prolong the life of your gelcoat. No need to raise it immediately, but at some point you should address it.
 
The CYA test is highly lighting dependant and should always be done in full sunlight with the sun to your back and sample viewed from about waist level. As others have said R870 is used in excess for the test and we have found that a single heaping spoon tends to be enough at most FC levels, Taylor just gives a larger margin of error saying 2 even spoons which we find generally just wastes R870.

Ike
 
I tested again last night - free chlorine is now at 31, combined is zero (EEEK! - I've turned down the SWG).

Somehow, adding 1.5kg of stabiliser has brought up the CYA levels to 90, overshooting the target of 70-80 I was seeking for the SWG.

That will learn me for putting in too much at once.

So its time to get some of the water out of the pool and refill. 10%-15% I would assume would get pretty close to 80.

Not sure why it ended up so high - it was less than 30 (ie could see the dot when the tube was full). I added enough to bring it to 80, and overshot.

The salt is way too high, so not a big deal to have to empty some of it. I might retest with a diluted sample and see what the results are.
 
You can use pool math to determine how much water too dump for your CYA level and salt.

You can do the CYA test a couple of times with the same pool water solution to make sure you get same readings. Are you doing it as Isaac-1 suggested to you ? It can be a little tricky.
 

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I've drained 10% of the water yesterday, and turned down the SWG - last test was 21FC, 0CC, 100 TA (I was measuring it wrongly before, using the green to clear change rather green to clear to red), 90 CH - haven't tested the CYA since it was very overcast.

Out of interest I tested the fill water - PH of 7.9 (?!!), TA 40, CH 50 (really soft water here).

Will test the CYA today I think. If its still 90-ish I will drain again. 80 I'll leave it alone.

There is still waaaay too much salt in there, and I need to re-orient the SWG as it forms an hydrogen pocket in the stock position when the pump is in low speed mode.

I'll get this thing sorted - eventually.
 
Good morning (here, anyway)

Your TA test is confusing to me. There is no intermediate clear stage. You should review your testing procedures and instructions in the kit. (edit...tell us what kit you have)

If you drained 10% of your water and refilled, you will have 10% less CYA. There is no need to restest.

Have you Read "The ABC's of Pool Water Chemistry" up in Pool School??
 
I tried that last night, much easier to see.

My reagents turned up from the states yesterday, and I also tried the salt test - 5,800 PPM - not a pretty test, lots of chunky bits at the bottom, and cleaning up after it was a chore.

Oh - and silver nitrate - I forgot how badly it stains skin. Woke up this morning and went outside, and I had a huge black stain on my fingers and hand. Darn.

I've got to turn down that SWG - FC was 28 again last night! Small pool + big SWG = lots of chlorine. At least nothing can survive in it!
 
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