Water test results - please advise

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M

matali

0
Jul 10, 2014
17
NJ
Hi,

I got TF-100 test water kit 2 days ago and started testing the pool water.
Initially we had low alkalinity (around 40 and low pH 6.9 according to pool store test), so 2 days ago we dumped around 25 lbs of baking soda. pH increased as well as alkalinity.

Here are the yesterday results:
TC 1
CC 2.5
pH 7.2
TA 130
CH 100
CYA ~100

It looks like TC is too low. We have chlorinator which was set to 6, now we set it to 7. Should we increase the flow even more?
CH 100 is OK? We have vinyl pool.

Thanks for any hints.

matali
 
Slow down! What kind of chlorinator? Is it a salt water generator, or a puck dispenser?

Trichlor pucks add chlorine, but they also add CYA, and they also are very acidic and drive pH and TA down. That sounds like your situation. Turning the chlorinator up is only making the situation worse. If CYA is 100 - and it's likely higher than that - you should repeat the CYA test using the dilution method described in Extended Test Kit Directions. Post 8, step 9.

Let's say your CYA turns out to be exactly 100, just for demonstration. Your minimum FC level should be 8!! :shock: The trouble is, if you try to boost FC from 1 to 8 using trichlor pucks, you'll also add another 4 CYA, which means FC needs to be a little higher, which means more trichlor, which means... It's a vicious spiral. So, you need to use something without CYA in it: bleach. http://www.troublefreepool.com/content/142-how-to-chlorinate-your-pool

The CH at 100 is fine for a vinyl pool. You can't damage the plaster because you don't have a plaster finish.

Have you read the ABCs yet? It might help you understand what we write and understand what those test results mean.

How does the water look?
 
read "The ABC's of Pool Water Chemistry" up in Pool School. It helps you understand why we test these parameters.

1. Your CYA of 100 is too high. 50 is about normal and will require a 50% drain of your pool but will make EVERYTHING else easier.

Once you get your CYA back to a manageable level, it will be fairly simply to SLAM your Pool (Look in Pool School) Next, continue that SLAM process until your pool sparkles. we'll help you every step of the way.
 
Richard320 said:
Slow down! What kind of chlorinator? Is it a salt water generator, or a puck dispenser?
Click to expand...
Puck dispenser (for chlorine tablets bought in the pool store)
Richard320 said:
Trichlor pucks add chlorine, but they also add CYA, and they also are very acidic and drive pH and TA down. That sounds like your situation. Turning the chlorinator up is only making the situation worse. If CYA is 100 - and it's likely higher than that - you should repeat the CYA test using the dilution method described in Extended Test Kit Directions. Post 8, step 9.

Let's say your CYA turns out to be exactly 100, just for demonstration. Your minimum FC level should be 8!! :shock: The trouble is, if you try to boost FC from 1 to 8 using trichlor pucks, you'll also add another 4 CYA, which means FC needs to be a little higher, which means more trichlor, which means... It's a vicious spiral. So, you need to use something without CYA in it: bleach. http://www.troublefreepool.com/content/142-how-to-chlorinate-your-pool

The CH at 100 is fine for a vinyl pool. You can't damage the plaster because you don't have a plaster finish.

Have you read the ABCs yet? It might help you understand what we write and understand what those test results mean.

How does the water look?
Click to expand...
The water looks good - crystal blue.

I am going to do this extended CYA test with diluted water, so I will have correct values.
Thanks!
 
duraleigh said:
read "The ABC's of Pool Water Chemistry" up in Pool School. It helps you understand why we test these parameters.

1. Your CYA of 100 is too high. 50 is about normal and will require a 50% drain of your pool but will make EVERYTHING else easier.

Once you get your CYA back to a manageable level, it will be fairly simply to SLAM your Pool (Look in Pool School) Next, continue that SLAM process until your pool sparkles. we'll help you every step of the way.
Click to expand...

I know you guys mainly use bleach, but I have full bucket of those chlorine tablets and the chlorinator. If I drain the water and let's say achieve 50 CYA, can I still use it?
 
I think I made a mistake regarding CC value. It is CC=0.5

I just checked my notes and compared with instructions from TF kit.
So from K-1000 test for Chlorine (the one with pH) I got the value = 1

From Chlorine Drop test: I had TC=2.5, as FC=2 and CC=0.5.
I will retest it tonight, but in case CC=0.5 - does it make any difference in your recommendations?

I understand that that Chlorine Drop test is more accurate... (I am sorry but all this pool and water testing is very new to me.)
 
Same recommendation. You still need to raise free chlorine above 8 for CYA= 100. http://www.troublefreepool.com/content/128-chlorine-cya-chart-slam-shock

Draining a bunch of water just means you'll have to do a bunch more rebalancing, and if you resume using pucks, in a month or so, you'll be draining again. And if somehow algae gets a start, you'll have to drain a whole lot more top get the CYA down to a manageable number where you can run the SLAM process.

Draining a bunch now or doing it in stages and watering the lawn with the pool water doesn't matter, as long as you maintain adequate FC for the CYA level. What does matter is stop adding CYA via pucks. They'll last for years, provided you keep the bucket closed. If you drain down to winterize, you can use them next spring to raise CYA at the beginning of the season. Your best bet to maintain that clear water is to maintain the FC using bleach. You'll find your pH and TA need less adjustment that way, too.
 
OK, thanks, I think I understand it now better:

I should stop using pucks to cut CYA level, measure CYA, and then increase FC (using bleach) to be within the range for given CYA.
If I want to have lower CYA, then I need to drain some water and then balance FC.

I understand it is better to have lower CYA and lower FC. Is there any other benefit (except cost of putting more chlorine into water)? What is the ideal level of CYA? Is my current leve CYA=100 safe?
 

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It is not necessarily "better" to have lower CYA. The high CYA just requires higher FC levels, just as safe, and the real issue is if you need to SLAM the pool with high CYA levels as the FC gets to be very high and require a lot of bleach.

Where you are I would think 30-40ppm would be plenty for the CYA. You CYA of 100 (ish, is it higher?) can be safe if you maintain high enough FC levels.
 
matali said:
OK, thanks, I think I understand it now better:

I should stop using pucks to cut CYA level, measure CYA, and then increase FC (using bleach) to be within the range for given CYA.
If I want to have lower CYA, then I need to drain some water and then balance FC.

I understand it is better to have lower CYA and lower FC. Is there any other benefit (except cost of putting more chlorine into water)? What is the ideal level of CYA? Is my current leve CYA=100 safe?
Click to expand...
Yes. :goodjob:

As long as the water stays clear and sparkly, there's no real problem from a health standpoint to having high CYA, as long as the FC level is correct. But here's the down sides: 1) Most test kits can't measure the high FC levels you need to maintain. The pool's appetite will be roughly the same, whether CYA is 50 or 100, but it's a daily drop from 10 to 8 instead of 6 to 4. So testing is one problem. You won't be able to just use the quick-check color block test. It will mean a full-on FAS-DPD test every single time. 2) the pH test becomes iffy when FC is above 10 and the reagent starts to react and will make it read higher than it actually is. At 100 CYA, you'll be maintaining 7 to 10, so it's do-able. But what if CYA is actually 120 or 130? Your minimum FC level is then 10, so your pH reading will always be suspect. 3) If you do develop algae, the shock level to kill it becomes so high that just the initial load of bleach to get it to shock level starts to cost as much as the water to refill it. And since you lose a percentage to sunlight, not a fixed amount, raising FC to some astronomical number, say 48 FC, means you lose huge quantities to the sun before it can even start killing algae.

I've maintained a pool with super high CYA and no opportunity to drain and refill due to water restrictions. I can tell you firsthand, it's a lot easier to maintain things with lower CYA.
 
So I will retest the CYA today (with this extended test) to see where we are.

By the way how easy is to drain the pool? How you discard the water (by watering the plants?). We have well and septic system on the property...
 
matali said:
So I will retest the CYA today (with this extended test) to see where we are.

By the way how easy is to drain the pool? How you discard the water (by watering the plants?). We have well and septic system on the property...
Click to expand...
In that case, I'd start doing it in steps. Drain off a few inches - whatever the lawn can absorb, and then refill. It will be slow going, but you can't just dump it all down the drain. If you overwhelm the septic tank, things will bypass the baffles and end up clogging the leach lines. You don't want that. Nor do you want to strain your well that badly. So a few inches at a time.

If you figure out your average depth, you might be surprised. If it's something like four feet average, then the diference between normal depth and bottom of the tile will be something like 3". That's 6%. If your drain is plumbed such that it;s possible to go below the skimmer, 5" would be a 10% reduction in CYA.

My plumbing is set up with a hose faucet on the return line, so I just connect a hose and drag it out wherever I want to water. If your filter has a "waste" setting, that's even faster. Or if you have a little sump pump sitting around, connect that to a hose and sprinkler and soak the lawn.
 
Thanks for all the replies.

I retested CYA using extended method, it was 120 and pH=7.2, FC=1.5 . We drained maybe 2 inches, refilled the water and dumped one big Clorox jug of 8.25% bleach.
Retested yesterday - CYA=150, pH=7.5, FC=5.5 (water crystal clear). After that drained 2 inches again and refilled the water. I will retest it today.
Obviously it looks that my CYA testing is not very reliable yet (hopefully the more I test, the better I get).

But why pH raised?

FC got much higher. I assume I should pour even more to compensate for high CYA level. However it is hard for me to pour more bleach because I know that chlorine is a toxic gas (although in water it forms HOCl) and the general recommendation is to have this level between 1 and 3. I have small kids and my daughter always swallow some water, so I am worrying about all of this. Any thoughts?

Thanks,
matali
 
First, why are you only draining 2" at a time? That is likely at best only replacing 5% of the water (and thus lowering the CYA by 5%) at a time and will take forever to get it down.

What is the pH of the fill water? That could raise the pH of the pool.

Finally, your FC is no where near high enough to prevent algae. At a CYA of 100ppm, you need a minimum of 7ppm to prevent problems. Likely you should keep it above 8 or 9ppm. See the FC/CYA Chart.

The 1-3ppm recommendation is based on no CYA in the water ... this is what is always stated because no one seems to understand the FC / CYA relationship. With CYA, the chlorine is much less harsh and not a concern. You can search the forum for the many threads discussing what chlorine level is safe.
 
Thanks, jblizzle!
Regarding the slow drain - I think we are too cautious (pool owners just for 3 weeks). The look of the water is deceiving :) Will drain more tonight and I will retest pH of my source water to be sure.

Regarding FC, I started searching other threads and found this written by chemgeek: Free Chlorine (FC) does not measure active chlorine, but rather the chlorine reserve or reservoir that is mostly inactive. which makes sense now.


By the way I just don't understand how those pool guys can work without knowing of this CYA/FC relation... I assume half (or most) of the pool owners that are using chlorine pucks have this kind of problems.
 
Sure, they have these problems and go in and spend $100 on the magic cure ... which does not work, so they buy the $100 super-terrific magic pill ... which also does not work. Then the pool store gives up, tells you a line about "chlorine lock" and that you need to replace water so you can start the cycle over. It is in fact a brilliant money making strategy ;)
 
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