Safe to swim?

[jenny2777]

Hi everyone!

First, I can't express how grateful I am for the wealth of information provided by this blog and group of people. THANK YOU!!!!

I'm wondering if it is safe to swim in a my pool at the present time. My pool developed an algae issue due to overuse of chlorine tablets, which we had been using for 30+ years of having above ground pools and never had an issue. I am preparing to drain by pool about 50% and refill my pool due to a a high CYA and have stopped using the chlorine tablets and converted to using only liquid chlorine. After refilling, I will SLAM to hopefully rid our pool of the algae problem. This morning, my numbers looked like this:

FC-5
CC-.5
PH-7
TA-90
CH-300
CYA-130/140

After using pool math, I added liquid chlorine and borax around 2:45/3:00 this afternoon according to results. At 7:15 this evening, my numbers looked like this:

FC-18
CC-.5
PH-7.2
TA-100
CH-300
CYA-130/140

I live in southeastern PA and it was an extremely hot day today. My question is I have 2 young children who really want to swim. I'm a little confused about what is safe and what isn't when dealing with issues such as mine. Any advice is so very much appreciated! Really stinks to be dealing with this on a holiday weekend, but I am so grateful for knowledge and guidance provided by this blog and it's members.

 

[mgtfp]

Up to SLAM level for the individual CYA level is usually safe for swimming.

Make sure that you can trust the CYA level, i.e. you should test yourself with a proper test kit, don't rely on test strips or pool store tests.

You should also consider that while fighting algae, you will likely create higher levels of combined chlorine. It is this cc that creates that typical "too much chlorine" feel, where it smells like in a public pool and you get red eyes.

CYA 140 is off the chart, but I guess slam level will be at about FC 60.

At this CYA you also have to make sure you have enough chlorine to actually do it's primary job, i.e. kill bacteria. Once your FC drops below about 5 (which can happen very quickly during an algae bloom), it gets unsafe from a sanitation point of view.

Start the drain/refill as soon as you can.

 

[Richard320]

Short answer: probably. Depends on the water clarity

You need three conditions met
1) Water is clear enough to see the floor. Even after swimmers have stirred it up.
2) pH between 7.2 and 8.0
3) FC between minimum and SLAM for your CYA FC/CYA Levels

If the kids do get in, put 'em to work. Figure out a game where they can scrub the walls for you. And at the end, have them create a whirlpool by running around the edge. That will settle anything in the center and make it easier to vacuum.

 

[doug wilcox]

AGree with above post
and just think your pool has to
be cleaner than the ocean, lake, river or pond
we swam in as children.

doug

 

[jenny2777]

Short answer: probably. Depends on the water clarity

You need three conditions met
1) Water is clear enough to see the floor. Even after swimmers have stirred it up.
2) pH between 7.2 and 8.0
3) FC between minimum and SLAM for your CYA FC/CYA Levels

If the kids do get in, put 'em to work. Figure out a game where they can scrub the walls for you. And at the end, have them create a whirlpool by running around the edge. That will settle anything in the center and make it easier to vacuum.

Thank you! The water is clear as of now, but haven’t let them get in because I wasn’t sure. My target FC right now is between 16-17. I am planning to drain and refill on Monday-tuesday as it’s the soonest we can get a water delivery (we have a well). So, trying to keep the FC up until then, and hopefully dilution will bring the cya way down. Any other suggestions? I brought the ph up to 7.2, but unfortunately raised the TA to 100. Can I do something differently?

 

[Richard320]

Thank you! The water is clear as of now, but haven’t let them get in because I wasn’t sure. My target FC right now is between 16-17. I am planning to drain and refill on Monday-tuesday as it’s the soonest we can get a water delivery (we have a well). So, trying to keep the FC up until then, and hopefully dilution will bring the cya way down. Any other suggestions? I brought the ph up to 7.2, but unfortunately raised the TA to 100. Can I do something differently?

7.2 is swimmable, and kids splashing will aerate it some and raise it more.

 

[jenny2777]

Up to SLAM level for the individual CYA level is usually safe for swimming.

Make sure that you can trust the CYA level, i.e. you should test yourself with a proper test kit, don't rely on test strips or pool store tests.

You should also consider that while fighting algae, you will likely create higher levels of combined chlorine. It is this cc that creates that typical "too much chlorine" feel, where it smells like in a public pool and you get red eyes.

CYA 140 is off the chart, but I guess slam level will be at about FC 60.

At this CYA you also have to make sure you have enough chlorine to actually do it's primary job, i.e. kill bacteria. Once your FC drops below about 5 (which can happen very quickly during an algae bloom), it gets unsafe from a sanitation point of view.

Start the drain/refill as soon as you can.

I’m using a Taylor k2006

Up to SLAM level for the individual CYA level is usually safe for swimming.

Make sure that you can trust the CYA level, i.e. you should test yourself with a proper test kit, don't rely on test strips or pool store tests.

You should also consider that while fighting algae, you will likely create higher levels of combined chlorine. It is this cc that creates that typical "too much chlorine" feel, where it smells like in a public pool and you get red eyes.

CYA 140 is off the chart, but I guess slam level will be at about FC 60.

At this CYA you also have to make sure you have enough chlorine to actually do it's primary job, i.e. kill bacteria. Once your FC drops below about 5 (which can happen very quickly during an algae bloom), it gets unsafe from a sanitation point of view.

Start the drain/refill as soon as you can.

Thank you so much!
I’m using a Taylor k2006c test kit, but have found the cya test to be challenging. Because it’s so high, I’m cutting the pool water with 50% tap water, then multiplying results by 2. Is there a better or more accurate way to test?

 

[jenny2777]

AGree with above post
and just think your pool has to
be cleaner than the ocean, lake, river or pond
we swam in as children.

doug

Thank you! Very true, didn’t think about it that way.

 

[Richard320]

I’m using a Taylor k2006


Thank you so much!
I’m using a Taylor k2006c test kit, but have found the cya test to be challenging. Because it’s so high, I’m cutting the pool water with 50% tap water, then multiplying results by 2. Is there a better or more accurate way to test?

Nope. That's it.

I started with over 200 CYA when I took over. I was lucky, I didn't have algae.Pool maintenance is much easier at lower CYA, I assure you.

 

[mgtfp]

How are you messing pH? Above FC 10 the chlorine interferes with most pH tests.

 

[mgtfp]

Because it’s so high, I’m cutting the pool water with 50% tap water, then multiplying results by 2. Is there a better or more accurate way to test?

You are doing everything right there. Dilute the sample until you get a reading below 100 and then scale up according to the dilution.

 

[jenny2777]

How are you messing pH? Above FC 10 the chlorine interferes with most pH tests.

I put the numbers onto pool math and followed the directions given. I’m trying to just keep the FC level up as instructed in pool math until I drain, refill and get the cya down so the numbers will be a bit more manageable with regard to the liquid chlorine level. I’m new to the TFP techniques, but after reading and getting my Taylor k2006c test kit, it all makes a lot more sense to me. Should I be doing something differently? I do have all of my information in my signature when I use my computer, but am replying from my phone right now, so I’m not sure if it’s still there.

 

[Richard320]

How are you messing pH? Above FC 10 the chlorine interferes with most pH tests.

Not entirely. If the FC/CYA ratio is normal, the initial pH test is usually pretty close to correct. If you leave it sit for five minutes or so, it may react with the reagent and give a falsely high reading. If the FC/CYA is up at shock level, especially if CYA is low, it will react almost instantly. Falsely high.

Since hers is reading low, and since her FC/CYA is barely in the normal zone I'd trust her initial readings.

Interesting thread on the high FC/pH test phenomenon, with some explanations Accurate pH test during shock levels with R-007?

The above is all true with Taylor stuff. I haven't got a clue what you use on the underside of the planet.

 

[jenny2777]

Nope. That's it.

I started with over 200 CYA when I took over. I was lucky, I didn't have algae.Pool maintenance is much easier at lower CYA, I assure you.

I appreciate

Nope. That's it.

I started with over 200 CYA when I took over. I was lucky, I didn't have algae.Pool maintenance is much easier at lower CYA, I assure you.

Is there a more exact way to calculate how much water to drain and refill in order to dilute the cya to a manageable value?

 

[mgtfp]

Not entirely. If the FC/CYA ratio is normal, the initial pH test is usually pretty close to correct. If you leave it sit for five minutes or so, it may react with the reagent and give a falsely high reading. If the FC/CYA is up at shock level, especially if CYA is low, it will react almost instantly. Falsely high.

Since hers is reading low, and since her FC/CYA is barely in the normal zone I'd trust her initial readings.

Interesting thread on the high FC/pH test phenomenon, with some explanations Accurate pH test during shock levels with R-007?

The above is all true with Taylor stuff. I haven't got a clue what you use on the underside of the planet.

Thanks for the explanation, Richard. Not much experience with the Taylor pH test. I am a bit colour challenged in the oranges, and therefore am using a pH meter. Didn't know that "high" FC for the Taylor pH test still has to be read relative against the CYA level. Good to know.

 

[mgtfp]

but am replying from my phone right now, so I’m not sure if it’s still there.

When you turn your phone to landscape you will see signatures also on a phone.

 

[Richard320]

I appreciate

Is there a more exact way to calculate how much water to drain and refill in order to dilute the cya to a manageable value?

Tap water has none, so if you want to reduce CYA by 50%, replace 50% of the water. You have an above ground pool, so just stick a tape measure in the water and get the depth and go from there. One caveat: leave a foot or so in the pool so the liner doesn't shift and wrinkle.

 

[MITBeta]

Percentage Replacement = 1 - (target CYA / current CYA)

Example: 1 - (40/140) = ~72%

That's if you drain first, then fill. If you do a no-drain water exchange it will be considerably more.

 

[jenny2777]

Percentage Replacement = 1 - (target CYA / current CYA)

Example: 1 - (40/140) = ~72%

That's if you drain first, then fill. If you do a no-drain water exchange it will be considerably more.

Thank you!
We are defintely draining on Monday or tuesday, just wasn’t sure how much. See the conversion with the numbers now it makes sense. That’s a lot of water, lol. Other than using the waste or backwash to drain from the filter, or a syphon then after, what else can I use to drain that much water?

 

[Chasarms]

You can buy a cheap pump at your local mega home store. It’ll take while by syphon, but it will work.

The more hoses you can get syphoning, the faster the process.

The easiest way for me to start a syphon is to use two hoses. Attach one to your outdoor faucet and the second to the end of the first. Place end of the second where you want it to drain. Place the junction of the two the the pool.

Turn on the water at the faucet. As soon as you’re getting good flow out of the end, separate the two hoses while keeping them underwater. Let the syphon hose fall to the pool floor and make sure there’s something to keep it there. It should keep running.

I’ve also done it by holding the end of the hose tightly to the return jet.