Testing for lower levels of TC, FC

[davethomaspilot]

Phizy,

I'd be very interested in following what you find.

I've have a new pool and maintained over six winter months using an ionizer, ozone injection, and a weekly dose of three scoops of powdered shock (yes, shock is chlorine). That's just what my pool builder setup for me and that was before I found this forum and started doing research.

I haven't had any staining or algae and crystal clear water, but I figure some chlorine to make sure the disinfectant level is adequate can't hurt. It doesn't take much to get significantly better protection than copper alone can provide, especially at 0 or low CYA. A little bit of copper also greatly increases the sanitation effect of FC.

I have an IntelliChem that doses chlorine to regulate ORP and acid to regulate PH. Before adding CYA, I'm going to monitor FC to see how much it varies in my pool during full sun days. At 0 CYA, the recommended minimum chlorine needed is based on a predicted decay rate of chlorine due to exposure to direct sunlight.

So, first I want to verify that. Shouldn't be hard to test give the VERY fast predicted decay of FC at 0 CYA using the FAS-DPD test.

Next, I want to see how much the FC decays with the IntelliChem actively regulating the ph and ORP. I'm thinking the TFP recommended minimum FC is based on having a buffer when only a single daily dose of chlorine is done, or maybe only a weekly dose. Might be different for a system that runs the pump and doses at frequently intervals during midday. Since their recommendations are for an "average" pool, average might exclude pools with automated dosers.

Just got the FAS-DPD kit yesterday and will start getting daily data. Please feel to email me with what you find out and I'll do like wise if you're interested in what I find out.

Good luck!

 

[needsajet]

50 ml sample size makes sense for 0.1 resolution. Just curious, does the circulation, UV and chlorination system run 24/7 ?

 

[Phizy]

When I shock the pool I run for 24/7. I shock in the evening and set the pump to half speed and then it kicks full speed at 7 am. The auto chlorinator is connected through the system so its "running" when the pump is.

 

[needsajet]

I'm thinking the TFP recommended minimum FC is based on having a buffer when only a single daily dose of chlorine is done, or maybe only a weekly dose. Might be different for a system that runs the pump and doses at frequently intervals during midday. Since their recommendations are for an "average" pool, average might exclude pools with automated dosers.

From what I've learned, with respect to FC, TFPC is based on a safe and effective target FC sufficient for the CYA level. There is also a minimum FC which allows for fluctuation in dosing and environmental factors. The levels are based on experience along with a sound understanding of pool chemistry. I don't know the percentage, but many, if not most, pools maintained using TFPC are equipped with automatic chlorine dosing. Although I'm relatively new to TFP, I've read an awful lot here, and I've never come across a TFPC method based on weekly dosing of chlorine.

 

[Phizy]

I agree. I have an autochlorinator. The original point of this forum post was on the ability to measure the FC/TC levels that are "lower than typical". I can always drive the samples down to the office and have it analyzed (for free) and will continue to do so as a check against at-home methods.

and I've never come across a TFPC method based on weekly dosing of chlorine.

 

[tim5055]

The store down the road from me will analyze for free using the Lemotte spin system.

Do not confuse the specificity of the results the spin systems gives with accuracy. One of the stores I stop by has a spin system and their results are seldom close to my hand testing. As common with testing the CYA is usually the worst, pH the closest. FC can be all across the board. The FC results may have something to do with cleaning/calibration of the machine as it can be close sometimes and off the wall others.

 

[Phizy]

Understood. This is why I have tested out the accuracy of their system after known additions of corresponding chemicals and calculating the resulting ppm. I've neglected to this point to note I'm an analytical chemist.
I have found the spin system to have questionable results at very low CYA. I've even dabbled with using photographs of the strips and matching color patches to calibrate a curve based on the euclidean distance from the Lab color space. Reasonably accurate provided the light is correct and white balance works. But...that was more for fun. If I had my way, I'd put an online system testing values every hour.