All of a sudden pool need a LOT more chlorine?????

[cfiiman]

Hey guys,

Still a newish pool owner (about 5 months). And I'm in SW FL. I have a 10,000 gallon pool and over the winter my pool like clockwork needed 1 cup of pool store chlorine a day to maintain level. All of a sudden I noticed it kept dropping, so when it got down to 3ppm (normally kept it at 7.5 b/c cya level was around 60ish) I put 3 cups in. That should have brought it up to 7.5 by the next day but it didn't, the next day it still registered 3.0 chlorine. So I did a cya test and it looks like that is really down from where it was, I measured about 25ish now (the test is fairly subjective though depending on how good you eyesight is). So I added 9 cups to see what would happen, and again it looks like after 24 hours it is back down to 3 which I don't even understand b/c that is what 3 cups did?!?! Anyway not sure what to do, I'm thinking of throwing a few pucks in b/c after learning they added cya I stopped using them 5 months ago and it appears to have worked by lowering my cya quite a bit. Can anyone help me with this, not sure what to do. My pool has been so easy and predictable and now i'm getting weird readings for some reason and it appears my chlorine is just burning off. I haven't shocked the pool forever should I do that? Any help is appreciated.

 

[kimkats]

Weird for sure! Let do this to start with okay? Run a full set of tests and post them here please. That will give a starting point.

Next add your chlorine to get you to your goal level with the pump running. Let it run for 15 mins and retest the FC. Let us know the results of that test. We can go from there to figure out what is going on.

Kim

 

[cfiiman]

Weird for sure! Let do this to start with okay? Run a full set of tests and post them here please. That will give a starting point.

Next add your chlorine to get you to your goal level with the pump running. Let it run for 15 mins and retest the FC. Let us know the results of that test. We can go from there to figure out what is going on.

Kim

Ok I'll run a full set in the morning and report back, I just don't get it.

 

[Divin Dave]

It may be that the pool stores liquid chlorine is a bit old?
Liquid chlorine become weaker with time, even if its in an unopened bottle. If it has become weak, that could be the reason for it.

 

[JamesW]

24 ounces of 12.5 % sodium hypochlorite in 10,000 gallons will only increase the FC by 2.3 ppm, not 4.5 ppm.

The sudden loss of CYA coupled with the sudden increase in chlorine demand might point to bacteria eating the CYA and converting it to ammonia. Are you doing CC readings?

Has the chlorine been down to zero anytime in the last few weeks?

What is the water temperature?

Any combined chlorine smell when adding chlorine.

 

[cfiiman]

24 ounces of 12.5 % sodium hypochlorite in 10,000 gallons will only increase the FC by 2.3 ppm, not 4.5 ppm.

The sudden loss of CYA coupled with the sudden increase in chlorine demand might point to bacteria eating the CYA and converting it to ammonia. Are you doing CC readings?

Has the chlorine been down to zero anytime in the last few weeks?

What is the water temperature?

Any combined chlorine smell when adding chlorine.

Hi, no the chlorine has not dropped below 3 ppm. Not sure how sudden the cya loss was as I hadn't tested it for 4 months. No I haven't done a CC reading in a long time b/c the pool was so predictable. I'm getting ready to do a full test in a few minutes and take a sample to the pool store for there test as well to compare. I'll post the results for you guys. The water temperature has rised from mid 70's to mid 80's in the last week or so as it was a hot sunny week, could that be part of it? How much chlorine should my pool use if nothing is going on? I mean like clockwork it only used 1 cup a day and everything was perfect, I'd like to get back to that. I'm guessing my CYA needs to go up a bit? Should I do pucks or just get some type of cya booster chemical? I should note the water looks beautiful and doesn't smell (not sure what a CC smell is can you explain?) There was/is a slight chlorine smell when adding chlorine but I thought that is normal?

 

[duraleigh]

The water temperature has rised from mid 70's to mid 80's in the last week or so as it was a hot sunny week, could that be part of it?

Absolutely. Water temp in the mid 80's will VERY much increase your FC needs. You will not be able to return to 1 cup daily until the weather cools back down.

CC smell is hard to describe but, to me, good FC smells a little bit sweet and fresh......maybe like laundry.

CC's smell a little acrid.....very common in indoor pools.

 

[cfiiman]

Ok guys, first off THANKS for all the help, I love this place! Ok on to my numbers. I was wrong last night (guess that is why I should only test in the daylight). Numbers this morning before the pump has turned on:

FC - 6
TC - 6
CC - 0
PH - 8 (normal for this pool, I have to add a couple cups of acid a week to keep it at 7.6 which I haven't done yet this week)
TA - 70
Calc Hrd - 320
CYA - Approx. 20-35 (see note below)

CYA Note- I say approx b/c this test is VERY subjective. You look at a dot until it "just disappears" with no instruction on how far away you are supposed to be when looking, how good your eyesight is (mine is excellent where if my wife tested it it may be much higher in her estimation), if you can just barley see it is that considered no good, etc. etc., so I always give myself a range when it starts to disappear at the high end (35) and when it is very hard for me to see it even when really focused on the low end (20ish).

That I believe this is all I can test for with my kit (Taylor K2006) except salt I think which I didn't do. As you can see my FC is still up there so maybe I jumped the gun a bit but I know 1 cup is not keeping it where it used to. In a 24 hour period 1 cup would keep it right where I wanted it (7.5) but that is when my CYA was twice this so I'm thinking that could have something to do with it as well right? Plus with my lower CYA my FC doesn't need to be 7.5 but more like 3 I guess. I'm also going to go to the pool store today because I need acid and I will have them test the water on their fancy machine (although I don't trust them doing it), but at least we will have 2 different readings, especially the CYA b/c to me it is so subjective the number is kind of arbitrary honestly. Thanks for any more guidance!

EDIT- I just had a thought that might be pertinent information. I have not cleaned my filter all winter, last time was maybe 4 months ago or so, could it be full of dirt/etc. that is using the chlorine (there is no pressure increase on the gauge)? Also I only run my pump 4 hours a day in winter and haven't switched back to 6 hours that I usually do in the summer, not sure if that matters or not b/c the pool turns over once every 2 hours.

 

[ping]

Don't bother testing at the pool store it will only add to the confusion.

I believe the only problem is that the pool is using up more chlorine due to the lower CYA level and warmer water.

Bump up the CYA 20 ppm or so and see how the pool reacts.

If you want to rule out organics as the cause of the extra loss of chlorine then run an OCLT. Use the search function to run that test if you don't know how to.

The CYA tube should be held at waist level with your back to the sun when testing for CYA.

 

[kimkats]

It is the warmer weather causing the increased FC use............I have gone from adding FC every 2 or 3 days to adding it daily in the last two weeks here in FL. If you keep a log of your testing with dates and conditions over time you will see a pattern that is related to the weather and season. This will help you head off problems before they happen.

Good job with your testing and noticing the increase in FC use.

Kim

 

[cfiiman]

Don't bother testing at the pool store it will only add to the confusion.

I believe the only problem is that the pool is using up more chlorine due to the lower CYA level and warmer water.

Bump up the CYA 20 ppm or so and see how the pool reacts.

If you want to rule out organics as the cause of the extra loss of chlorine then run an OCLT. Use the search function to run that test if you don't know how to.

The CYA tube should be held at waist level with your back to the sun when testing for CYA.

This was my initial thought as well. How should I get the CYA level up, with Pucks or buy something special?

It is the warmer weather causing the increased FC use............I have gone from adding FC every 2 or 3 days to adding it daily in the last two weeks here in FL. If you keep a log of your testing with dates and conditions over time you will see a pattern that is related to the weather and season. This will help you head off problems before they happen.

Good job with your testing and noticing the increase in FC use.

Kim

Thanks Kim, can you tell me how much chlorine you are adding daily now? I have a 10,000 gallon pool.

 

[kimkats]

I am at 25,600 gals............I add 7.5 cups a day. That is a little higher but I am SO gun shy of an algae outbreak that this level makes me happy. Adjust for your pool size and test to see what it is at night time. IF it is too low after a full days sun then add more the next day until you find your pool's amount.

Kim

 

[ping]

The pucks will raise it slowly and you will need to keep track how many you have used and calculate the amount of CYA they will add with each puck. It is easier to just add the CYA at once and be done with it, but it is your decision on what works best for you.