TFP is a godsend

[JEB123]

This is my first post, hope I'm in the right place! First of all, I have to thank all of you, I've learned a lot here. I had my filter crack after many years and replaced it with one that was way too small for an inground and the water was always cloudy. After a couple of months of high pressure and cartridge washing every other day I bought the 120 square ft Hayward and learned the importance of good filtration for a sparkling pool! I also learned the horror of using Dichlor pucks and having my CYA shoot up over 100+ in no time! Replaced about 30% of the water and with the help of lots of rain got it down to around 85, still have a long way to go but at least it's crystal clear. The only problem I have is small amounts of algae starting to return every couple of days. I'm guessing that will disappear with lower stabilizer levels allowing the FC to work? pH is high but I learned on here that high FC will give false pH readings, correct? FC has been high for two weeks and won't seem to come down! Why could that be?
Right now I have:
FC = 10
pH = 8.0
TA = 100
CYA = 100+
CH = 300
Can't recall my CC, I'll test and post it later.

 

[JasonLion]

Welcome to TFP!

With FC around 10, the PH test should be usable, probably fine, maybe 0.1 high.

When CYA is very high the FC level takes a long time to come down.

Have you actually measured a CYA level of 85, or is that just an estimate? When CYA is over 100, the common test will report CYA as 100, so it could actually be much higher.

 

[JEB123]

Hi Jason, thanks for the welcome! The CYA is measured, the scale on the tube looks logarythmic so it may have been 150, 200 or more it seems. Should I try a diluted test? Do you think that's a valid chlorine reading? If so why does the algae keep returning?

 

[zea3]

If your CYA is 85 then your daily FC target is 7-12. If you are consistently keeping FC above 7 and algae keeps recurring then your CYA is probably much higher than you think. Try mixing 1 part pool water to 1 part tap water and run the CYA test on that mixture. Double the result to approximate how high the CYA is measuring.

 

[JEB123]

Thanks, I will try that. BTW, do you guys know if there is any truth to the story about the screen structure helping maintain chlorine levels by partially blocking UV as well as keeping water temp lower? My father was a pool man for many years and he would always tell me that. He passed in 09 and I always kept the pool fairly well until the filter/ Dichlor puck disaster. I would just check pH and Chlorine levels before, now I've had to really learn the missing chemistry links! Thanks TFP!

 

[zea3]

I think it depends on the screen material. I know they used to sell screens they claimed blocked UV rays, however UV is good for the pool as it allows CC to burn off naturally. People pay good money to put in UV systems! (only worth it for commercial or indoor pools) You want chlorine to be consumed because that is its job, oxidizing bather waste. You just want it to be consumed at reasonable rates for the amount of use the pool gets. Shading the pool will keep the water a little cooler and the air will feel cooler as well.

 

[JEB123]

That's true, I was looking at a UV sanitizer system recently, says it eleminates chemical use by up to 90%. Sounds like a good idea, but I wonder what the power consumption is like! That may offset the decrease in chemical costs.
Thanks for your advice zea3! Hey is that Esther Williams?

 

[JasonLion]

UV helps a great deal in a heavily used commercial pool. But in a lightly used residential pool it does essentially nothing. With heavy bather load chlorine alone can't keep up and UV is a wonderful add-on. But in a residential pool chlorine alone is far more than enough, and there is nothing left for UV to do.

 

[jblizzle]

Back to the CYA question did you measure 85ppm or estimate it based on the amount of water you replaced. Whether it is 85 or 100+, you would still be better off replace at least half the water.

What test kit are you using?

 

[zea3]

That's true, I was looking at a UV sanitizer system recently, says it eleminates chemical use by up to 90%. Sounds like a good idea, but I wonder what the power consumption is like! That may offset the decrease in chemical costs.
Thanks for your advice zea3! Hey is that Esther Williams?

Yes, my avatar is the fabulous Esther Williams! +1 for Jasonlion's take on UV systems. If you want more info use the search box at the top right and search for "uv systems".

 

[JEB123]

UV helps a great deal in a heavily used commercial pool. But in a lightly used residential pool it does essentially nothing. With heavy bather load chlorine alone can't keep up and UV is a wonderful add-on. But in a residential pool chlorine alone is far more than enough, and there is nothing left for UV to do.

Good to know, I was actually thinking about it! D'oh! Well, here's some new readings from this morning:
FC - 3.2
CC - 0.2
pH - 7.6
TA - 80
CH - 225
CYA - 90
SI - 0.15
Now looks like FC has finally dropped, CYA still high. Should I just add chlorine and wait or go ahead and replace more water to not waste the chlorine?

 

[jblizzle]

Your FC is too low for that CYA level. I would replace half the water.

 

[JEB123]

I replaced about a third of the water and it went from 100 to 90. Guess I'll have to dump more. Does anyone in Florida know about the county footing the bill for filling a pool? I heard that they do. Man, I hope it rains a lot more!
Thanks jblizzle.

 

[bridgman]

If replacing 1/3 of the water took it from 100 to 90 it's likely the original level was higher than 100. Unless you were diluting the pool water 1:1 with tap water and doubling the test result the tests generally max out around 100.

 

[JEB123]

If replacing 1/3 of the water took it from 100 to 90 it's likely the original level was higher than 100. Unless you were diluting the pool water 1:1 with tap water and doubling the test result the tests generally max out around 100.

Yeah, you're right the first reading where I was getting over 100 was straight pool water, the 90 is diluted so I know that's accurate. It was probably sky high before . Anyhow, I guess 50% is the way to go now. Thanks!

 

[JEB123]

Well, replaced fifty percent of my water and here's the readings:

FC 2.5
CC 0.5
pH 8.0
TA 75
CH 175
CYA 45 woo hoo!
SI 0.2
Water is nice and clear, algae is starting to come back already in spots. Should I add acid to correct pH or
SLAM it first to kill of the remaining algae? Also, this pool is old and has returns on one end one high and one low. On the diagonal end are steps, and this area appears to have bad circulation so algae forms here fast. Is there a fix for this other than breaking concrete to add returns on the other end?

 

[bridgman]

I think "add acid to correct pH then almost immediately (30-60 minutes) SLAM" is the correct answer.

 

[jblizzle]

A prerequisite of the SLAM process is lowering the pH to the lower 7s. Verify after 30 minutes and SLAM away.

 

[JEB123]

I need to re-read the slam procedure and levels, thank you both! Should I just start a new post about the circulation issue? Sorry, I'm kinda new to forums!

 

[jblizzle]

Keep the questions here for continuity of story.