intellichem ph probe way off @ 4.6

[IQMike]

Can too much algeacide affect the probe reading?

I screwed up this year, I ran out of shock and I was late in adding CYA to my prfectly balanced pool thinking i will run the SWG 12 hrs/day to compensate. well that didnt work as the Fc was always around .8 to 1 ppm and the walls started to green up even though the water was crystal clear.

got a delivery of shock and cya. Dissolved the cya over a few days and settled in @ 40 ppm while the ph dropped to 7.1. shocked the pool to well over 12 ppm.. i stopped counting drops as not to waste the reagent. Brushed the walls. the ph shot up but selled down after a few days. 3 days later my FC was around 8 ppm but walls still had green stains in a few areas. went to the local walmart and picked up the HTH 30% algeaguard that they carry to give that a try. was heavy handed and put in twice tha recommended amount thinking more is better / faster. Water was a little hazy for 2 days but now perfectly clear. Green stains disappeared and water looks amazing

Current chemical balance via taylor K-2006

fc = 3.8 ppm
cc =.2 ppm
ph=7.6
cya =40
ta=60
ch=350

salt =3300 ppm

so far evrything is great.

a few days later i check the screenlogic app and see the ph @ 7.2, the next day, 6.8.

I test the water and ph is 7.6.

after some rain the probe is reading 5.9, again i test the water in the pool and at the probe flow bowl and its 7.6.

Right now the probe reads 4.6. I removed probe to clean it with brush and detergent and no change in reading. going to acid clean later and see.

the only variable is the algeacide. what else could explain a slow steady decline in probe readings?

it seems too much of a coincidence that the probe failed or the cable went bad so thats why i'm suspecting the algeacide.

any thoughts?

 

[Texas Splash]

Hello IQMike and welcome to TFP! I see you haven't received a reply yet on your post. We had some web site problems yesterday, so I'm not sure if anyone ever actually replied or not. I just wanted to let you know we haven't forgotten about you. A few comments about your concerns:
- You have the Taylor 2006 . That's great so YOU are on control of readings.
- Please refer to the link in my sig titled "Chlorine/CYA Chart". That is KEY to your success. You will see what your FC "should" be compared to your current CYA. Anytime it drops below the target (certainly below the minimum) you are susceptible to algae. That's probably what happened to you before.
- We do not advocate the use of algaecides or many pool store products. Typically they mess-up water readings. Save your money and stick with your SWG and/or regular bleach when you need to hit the FC level harder. A properly chlorinated pool (based on the CYA chart) will keep your water clear.

If your water ever gets cloudy or you see green again, follow our "SLAM" method (link below). All the other links below are quite valuable to you as well.

Having said all that, this reply should get your posting updated back to the top of the queue where others may chime-in a reply as well. I hope this info has helped you. Thanks for checking-in with TFP, and have a great day.

 

[IQMike]

Hi Tex and thanks for the welcome. this site is invaluable and i have learned so much browsing the forums. i wish i found this site before i switched from trichlor to swg. Being new to pools, i did what the previous homeowner did. I was using test strips and didn't yet comprehend the ph rise relatonship to swg and ended up with alot of scale on my brand new gunite surface due to high ph over the winter. Expensive lesson. It is this scale that becomes stained from the algae. I was considering an acid wash but i think i'll do more harm than good so i decided to live with my sandper walls.

So I embarked on a mission to take full control of the situation going forward.

Dumped the test strips in favor of the K2006 and I try to keep the FC at 1/10 of the CYA reading while keeping water balance as close to 0.00 as possible.
Ripped out all the old equipment including the new hayward swg (ebay) and went full pentair with easytouch, intelliflow vf, intellichlor, intellichem, and intellibrite 5g with screenlogic interface.
replumbed all above ground piping with 2" to ease flow restictions.

Back to my issue, I was using houshold bleach as shock and had dumped in 8 gallons at night which didn't make a dent on the green walls and had practically no FC within a day. So I ordered some cal hypo 73, which i get delivered to my door for around $2/lb, added the cya, cal hypo and in a moment of weakness and stupidity added the algeacide.

I'll never do that again as now when the kids spash around, there is some residual foam on the surface which was never there before and takes some time to dissipate.

I did figure out the PH probe issue though. as I suspected, the acid clean didnt work so I swapped the cables on the pc board and probes, and the ph reading shot right up to where its supposed to be. Of course the ORP reading is now way off.

both cables measure the same resistance which is really strange why one cable gives such a bad reading. I guess there might be an inductance or capacitance that is forming within the bad cable and throwing off the readings.

Well, thanks to all the members who contribute their knowlege.