SWCG pool tested FC @ 9 using test kit. Is this even possible?

[Charlie Bezzina]

Hello.

I'm very new to managing a pool and this is my first attempt at using a quality test kit. I'm a bit surprised with the results actually..

I received my clear choice labs test kit and gave it a go today. (Up untill today I have been using my 4in1 twice a week and pool shop fortnightly.)

According to the ccl test kit my results are as follows..

FC 9.0
CC 0.5
PH 7.5
TA 80
CH 350
CYA 40

Now the FC really surprises me for a couple of reasons.

1. When using the 4in1, the bleaching of the DPD is apparent, but it is not lighter than the 5.0 marker.
2. The pool store test consistently shows my free chlorine to be 5.5
3. Most importantly, my chlorinator only runs for 8 hours overnight at 20% output.

I initially thought the dpd1 and the pool shop tests were showing my fc to be higher than reality given my chlorinator settings, but it seems I was wrong.

I followed the test kit instructions carefully, and the general consensus on this site is to trust the test kit, so I'm wondering what is going on. Am I under estimating just how efficient my SWCG is?

 

[PoolStored]

z

 

[mknauss]

Let's see if @needsajet can help you out. I do not have the data for your SWCG but as you are in winter, I suspect your SWCG could be adding more FC than the sun is burning off each day.

 

[Charlie Bezzina]

Hello mknauss.

FYI. The SWCG uses a Hayward "T-9" turbocell and ORP control is disabled.

 

[Newdude]

Hey Charles !!! Your cell is rated for 2.6 X the volume of your pool. (Give or take). It will probably need to be off for some days with you guys in winter as Marty said.

Great job sourcing the kit !! It can be real tricky for a lot of people.

 

[Charlie Bezzina]

Hi Newdude. I've dropped the chlorinator down to 10% now, but given the huge difference between the tests, I'm only guessing...

Brett from CCL is going to send me a replacement reagent, so I will compare again later next week.

 

[needsajet]

Hi Charles, yep at this time of year very little chlorine is needed when the water is clean. All good and FC at 9 is not surprising nor harmful. You can probably set to 0% for a few days, then back up to 10%, or reduce filtration time down to 4 hours. My pool is similar size and 3 hours keeps the water sparkly clean through winter. Cheers

 

[Charlie Bezzina]

G'day needsajet.

The neighbours camphor laurels (approx 25m tall) started dumping their leaves into the pool after the rain on Sunday and I know this will continue for a month or two this time of the year, so I'm expecting my chlorine usage is about to change drastically.

So far the water is as clear as glass, I really hope to keep it that way!

Thanks for the advice.

 

[mouse23]

I wonder if there is an viable alternative way to test when FC is above the range of the FC test kit.
Fill the test tube halve way with the water to be tested and and the rest of the way with distilled water. So, 50-50.
Then do the test and multiply the result by 2. Anybody ?

 

[mknauss]

I wonder if there is an viable alternative way to test when FC is above the range of the FC test kit.

The FAS-DPD is very accurate to 20 ppm FC and reasonably accurate to 50 ppm FC. How much higher do you need?

 

[needsajet]

I wonder if there is an viable alternative

I was thrown off by that picture as well. That's a picture of the test method from the 4 in 1 small poolkit. The CCL test kit that Charles has is the identical test to the FAS-DPD used in the TFT and Taylor kits, so it's a drop-based test that Charles has and he'll be able to do it with normal accuracy.

Mate, yeh, mine lost a bit of FC that last few days (just now added some bleach). I use 8 hrs pump time in summer, around 4 hrs in winter, but higher SWCG %. I have my SWCG off at the moment, just trying the way they do it over in America (not running it when water is cold). The other pools I look after are all continuing with SWCG through winter.

 

[Charlie Bezzina]

Yes, the CCL test kit has a fas-dpd test. Apologies for any confusion.

I attached the dpd1 test result photo just for comparison. I would expect it to be more bleached at a pH of 9. A photo of the completed fas-dpd does not show anything useful so I did not attach one.

Heres a photo of the neighbours trees... Crazy huh.

 

[cowboycasey]

Those are some trees

 

[mouse23]

The FAS-DPD is very accurate to 20 ppm FC and reasonably accurate to 50 ppm FC. How much higher do you need?

I don't have an FAS-DPD test kit. My test kit only goes to 5ppm

 

[mknauss]

Then you need one. It is very difficult to manage pool water chemistry properly without a FAS-DPD test kit.

FAS/DPD Chlorine Test Kit

tftestkits.net

 

[mouse23]

Then you need one. It is very difficult to manage pool water chemistry properly without a FAS-DPD test kit.

FAS/DPD Chlorine Test Kit

tftestkits.net

Thank you. I must get one then. I still like to know if the methodology in my question is a good one. I don't have an alternative way to double check like you pro's may have.

 

[needsajet]

I still like to know if the methodology in my question is a good one.

The colour intensity tests for FC are reliable to answer yes/no; Is there chlorine in the water, or not?

Hence why the FAS-DPD test is the way to go. You can order it individually if need be, or get a full kit such as TF-100 Test Kit ™-BACK ORDERED TIL 08/15

There are a couple of tests where dilution can be relied on, but FC is not one of those. If reduced accuracy is OK for FC, then sometimes it's useful to do a 5ml test rather than 10ml, but with FAS-DPD.

 

[mouse23]

The colour intensity tests for FC are reliable to answer yes/no; Is there chlorine in the water, or not?

Hence why the FAS-DPD test is the way to go. You can order it individually if need be, or get a full kit such as TF-100 Test Kit ™-BACK ORDERED TIL 08/15

There are a couple of tests where dilution can be relied on, but FC is not one of those. If reduced accuracy is OK for FC, then sometimes it's useful to do a 5ml test rather than 10ml, but with FAS-DPD.

Thank you for your reply. So in essence, it is doable but not reliable.

 

[Charlie Bezzina]

Hi @needsajet. My free chlorine has been rising over the past few weeks, I'm up to 14 now. That is 2x higher than max recommend for my cya and only 3 shy of doing a slam!

Have you noticed a change in weather that has reduced your chlorine consumption?

 

[Newdude]

My free chlorine has been rising over the past few weeks, I'm up to 14 now. That is 2x higher than max recommend for my cya and only 3 shy of doing a slam!

Trust me its a GREAT problem to have !!! A little wasteful of SWG lifespan....... but dont worry.... literally a couple hours subtracted from 10k hours.... you'll never know.

So you're overproducing which is common this time of year anywhere its cooling off. We all need to adjust down every couple of weeks as the daily demand decreases. In the spring its the exact opposite. You test to spot the trends of the daily demand increasing with a higher sun angle and longer days. Sometimes you overshoot like im guessing happened to you here.

Are you still down under or did you move to the northern hemisphere ? Either way, shut the SWG off and let the FC drift back down to in-range. Once its in range, or preferable slighty over target range, fire up the SWG at a setting / runtime lower than you have at the moment and test daily to see if you need to tweak it again.