Calling all you experts... FC good, No CC, but cloudy/murky water... Please help

[bbrock]

Hi TFPers,
Happy Father's Day to all us dad's.

Uncovered the pool this afternoon only to see cloudy/murky water. Just last weekend, water was clear; could easily see the screws on the main drain cover. Now, I can see my main drain, but can't really make out the screws. Some background info: been covering the for about 1.5 mo. now, regularly add 12.5% chlorine (every 2-3 days about), test FC and pH every 2-3 days, VS pump is on 3 hr during day at 2400 RPM for solar/Polaris and 17 hr overnight at 800 RPM from 1800-0600, filters are new as of 4/15. Performed full testing:

pH 7.4
FC 6.0
CC 0
TA 60
CH 1150
CYA 30
temp = 91

Now, I don't understand what could be happening. When I got pool cover installed, I had a thread going about covers, and I remember reading a response that covers could cause some wackiness with testing/numbers. How could my water lose clarity all of a sudden (within a week or so)? How could it be murky/cloudy and the CC be 0?

The only thing I notice from my full testing today (I perform full testing 1x/mo. but test FC, CC, pH usually 2-3/wk) is that my CYA is lower than I expected. Last mo. it was 40. How could my pool be consuming CYA? For the last 1 or 2 mo., my chlorine goal has been 3-7 based on CYA 40. When I add chlorine, I usally add enough to bring up the FC to the upper limit of my range. FWIW, even with the pool cover, I'm losing about 1 ppm FC/day

I appreciate all the help. Tx.

Edit: I would have supplied pics, but can't find my phone.

 

[bbrock]

Gonna go to my local Leslie's to have them test so I can compare. Since I have been TFPing it for over a year, I have not needed anyone else to test my water. Gonna compare results.

I really think it has to be something related to using the pool cover. What that is, I have no idea. This time last year, I was not covering the pool.

 

[tim5055]

You do not have to have CC's to have issues going on. In an outdoor pool in nice sunny California the CC's can get buned up quickly by the sun.

Skip Leslie's unless you buy your chlorine there and just drop the pH a hair and SLAM away.

 

[Texas Splash]

Hello TX! I'm going to chime-in here to get this thread at the top of the queue so others can reply as well. You seem to have a firm knowledge of your water and pool's history, yet something has gotten off-tracks. There could be a couple possibilities depending on all the facts we receive. Please answer/clarify the following please:
- How often (days/hours) is the cover on?
- CYA drop of 10 ppm; with water restrictions over there I'm assuming no water change correct?
- Have you performed an OCLT to record the loss of FC overnight?
- So you don't perform FC tests everyday correct? Have you ever come home to find it below your target or minimum?

As I said, there are a couple possibilities that might explain your situation. Your reply will not only help everyone reviewing, but should also keep your post at the top of the queue. Thanks for posting!

- - - Updated - - -

Tim is spot-on .. don't waste the gas going to the pool store. You have the power!

 

[mas985]

The pool cover combined with solar will raise the water temperature which in turn makes it easier for an algae bloom to get started and will also increase the FC extinction rate. You posted a FC level that is fairly high compared to the CYA level but that doesn't always tell a full story. With manual dosing, there tends to be more dips in the FC levels and with a CYA of only 30 ppm, you could have some significant dips that would allow algae to get started.

How often are you dosing with CL?

When do you usually add CL?

What is the FC level right before you dose?

 

[bbrock]

Seriously Tim? Wouldn't the CC be present to inform me of a problem? I greatly appreciate the response/suggestion. But, for my education and also prevention in the future, it would be helpful is I could figure out what happened/how did things get like this?

If it could be related to using a pool cover, I will say then it is not really worth it to me, even despite the fact that it helps with evaporation and I think my H20 district is requiring it. Just not worth it b/c when I get things back to normal, hopefully, this could happen again later in the summer, especially if I'm guessing it could be related to the pool cover usage. Thing I don't understand is how could a "problem" just spontaneously erupt if I regularly keep everything in line and am on top of keeping chlorine in range based on my CYA.

 

[tim5055]

Well, if you want to prove/disprove anything growing in the water take the FC up to 8ish at sunset. Let the pump run to circulate the water 30-60 minutes and take a chlorine reading after the sun is off the water. Take another before the sun is on the pool in the AM to prove if anything organic inthe water is consuming the chlorine.

Overnight FC Loss Test (OCLT)

 

[heugeneo]

I posted a similar question last week, to which no one answered, but I'll tell you what worked for me. My situation was almost exactly like yours, and I passed multiple OCLTs. My PH was 7.4 so I added enough acid to bring it down to 7.0. I could almost immediately see the water start to clear. By the next morning water was crystal clear. I don't know why or how it worked but that was the only thing I changed. Don't know if it will help in your situation, but may be worth a shot if nothing else helps.

 

[pooldv]

Yes, it is entirely possible to have algae growth without CC. I let warm water, lots of swimming and not enough testing sneak up on me a week ago. Last Saturday my FC was 1.5 and I saw some algae spots. Had to SLAM last week. CC was 0 the whole time.

Cloudy water is almost always algae and algae is almost always caused by letting the chlorine level drop below the minimum level for the CYA, Chlorine CYA Chart

It is important to keep chlorine at target level at all times, aim higher before and after lots of swimming. It is safe to swim with chlorine up to shock level. So, aim higher not lower. We've been swimming in FC of 25 all week with CYA of 70.

 

[bbrock]

Hello TX! I'm going to chime-in here to get this thread at the top of the queue so others can reply as well. You seem to have a firm knowledge of your water and pool's history, yet something has gotten off-tracks. There could be a couple possibilities depending on all the facts we receive. Please answer/clarify the following please:
- How often (days/hours) is the cover on?
During the work week, cover could stay on for 5 days straight. On a swim day, which is usually 2-3 days per week, cover has been off averaging about 2 hrs.

- CYA drop of 10 ppm; with water restrictions over there I'm assuming no water change correct?
No water change. Added normal amount of water about 1.5-2 weeks ago to top off d/t normal evaporation. This top-off was after having had the cover on for about 1 mo. Without the cover, I am usually topping off 1x/wk.

- Have you performed an OCLT to record the loss of FC overnight?
Not since I just discovered this situation today. Can try to do over tonight, but could be tough for me given my AM work schedule/departure from my hm. Can this OCLT be performed if the restest is at 0400-0500 in the morning? That too early?

- So you don't perform FC tests everyday correct? Have you ever come home to find it below your target or minimum?
Only possibly this week. But I'll explain. Just this past week, I was transitioning to the way I was testing/adding FC/pH/CC last summer. That is I would test the FC, pH, and CC 1x/week and then add accordingly. If, for instance, the test showed my FC was 5 and my upper target FC goal is 7, I would use Pool Math to add the appropriate amount of 12.5% chlorine. Regarding just the chlorine, in this example I would add 39 oz. given a CYA of 40 (what my CYA has been before testing today). Then, 2-3 days later I would skip testing and just add 39 oz chlorine. And, I would repeat that again in another 2-3 days and add that same amount of chlorine. I would re-test the FC, pH, and CC again the next week and adjust my subsequent chlorine additions based on that re-test. Make sense? I would do it this way for speed, and also to save FAS-DPD reagent.

Now to answer your "Have you ever come home to find it below your target or minimum?" This may have occurred 1x this last week. I don't have my phone, so I can't confirm dates/days. But, I think I performed my FC, CC, pH testing and adding last Sat. 6/13 night. I added FC to bring up my level to 7. If I recall, I added 39 oz chlorine to go from 5 to 7. I re-added 39 oz. on Tues. 6/16. On Wed. 6/17 I re-tested b/c it had been warm this past week and I was concerned. It showed a FC of 5. It was then that I was alarmed b/c I wondered how could I have a FC 5 when I just added the night before to 7, or so I thought. So, long story short, possibly/maybe it could have dropped to 3 or below on Wed. 6/17. But, the thing is though even if it dropped to a FC of 3, couldn't that be fine especially if my CYA is 30? Maybe my CYA was 30 longer than before today. Last time I retested CYA was about 1.5 mo. ago and it was 40 at that time (I still don't understand what could have dropped it; I think I read something by Chem Geek one time in which he stated that CYA can be consumed. I will have to verify/search.)

As I said, there are a couple possibilities that might explain your situation. Your reply will not only help everyone reviewing, but should also keep your post at the top of the queue. Thanks for posting!

- - - Updated - - -

Tim is spot-on .. don't waste the gas going to the pool store. You have the power!

Okay, I skipped Leslie's. Tx.

 

[pooldv]

I posted a similar question last week, to which no one answered, but I'll tell you what worked for me. My situation was almost exactly like yours, and I passed multiple OCLTs. My PH was 7.4 so I added enough acid to bring it down to 7.0. I could almost immediately see the water start to clear. By the next morning water was crystal clear. I don't know why or how it worked but that was the only thing I changed. Don't know if it will help in your situation, but may be worth a shot if nothing else helps.

Sorry, we did miss your post. I just replied and I will reply here too since if is relevant to this thread also. My hypothesis is that chlorine is more efficient at lower PH and that you would have achieved the same result with higher chlorine level.

 

[bbrock]

The pool cover combined with solar will raise the water temperature which in turn makes it easier for an algae bloom to get started and will also increase the FC extinction rate. You posted a FC level that is fairly high compared to the CYA level but that doesn't always tell a full story. With manual dosing, there tends to be more dips in the FC levels and with a CYA of only 30 ppm, you could have some significant dips that would allow algae to get started.

How often are you dosing with CL?

When do you usually add CL?

What is the FC level right before you dose?

The pool cover combined with solar will raise the water temperature which in turn makes it easier for an algae bloom to get started and will also increase the FC extinction rate. You posted a FC level that is fairly high compared to the CYA level but that doesn't always tell a full story. With manual dosing, there tends to be more dips in the FC levels and with a CYA of only 30 ppm, you could have some significant dips that would allow algae to get started.

How often are you dosing with CL?

When do you usually add CL?

What is the FC level right before you dose?

#1: Usually I am adding every 2-3 days. Before today, I was running on the impression that my CYA was 40, which it was the last time I tested it about 1.5 mo. ago. So, 40 has been my basis. I don't know how it could have dropped to 30 within 1.5 mo.
#2: At night when my pump is running at 800 RPM. Sometime I wonder if that is an adequate RPM to circulate the chemicals, but I figure it is good enough b/c I have my VS pump programmed at 2400 RPM during the day.
#3: Besides this past Tues. 6/16 I usually test before I add. Given my CYA of 40, before today, my FC has been anywhere from 4-6.5 before I add FC

 

[mas985]

How are you testing FC and cya?

At that water temp and cya level, I am surprised you can go 3 days without adding CL.

 

[bbrock]

Yes, it is entirely possible to have algae growth without CC. I let warm water, lots of swimming and not enough testing sneak up on me a week ago. Last Saturday my FC was 1.5 and I saw some algae spots. Had to SLAM last week. CC was 0 the whole time.

Cloudy water is almost always algae and algae is almost always caused by letting the chlorine level drop below the minimum level for the CYA, Chlorine CYA Chart

It is important to keep chlorine at target level at all times, aim higher before and after lots of swimming. It is safe to swim with chlorine up to shock level. So, aim higher not lower. We've been swimming in FC of 25 all week with CYA of 70.

Tx for the reply. I never have used the target chlorine off the Chlorine CYA chart, rather just adding to high range for my CYA based on Pool Math. I know the target chlorine is the midpt between in the FC range, but is that really important? I thought it was more important to keep it above minimum.

As for the swimming in FC of 25 or >10, I have read otherwise. Again, to refer to stuff read by the wise Chem Geek, it is not advisable to swim until the FC drops to below 10. Don't ask me exactly why, but he laid out a good reasoning for it. I have 2 year old twins, so I would rather error on the side of caution and keep them out until the FC is at a safe level to swim. If that means 10, and a period of not using, then that is how it has to be. It just sucks knowing that it is warm air temps, my water is nice and warm and, and I am going to have to stay out of it until all this is over.

 

[bbrock]

How are you testing FC and cya?
Before this past Tues. 6/16, I test FC w/ my TF100 using the FAS-DPD before adding. Last summer I was testing w/ the FAS-DPD at the beginning of the week, adding the needed chlorine, but then testing the chlorine w/ the OTO 2-3 days later, ensuring I had chlorine, then adding Cl to the high range given my CYA. That seemed to work. But now with this pool cover and much warmer water temps than last summer I don't think I can do that anymore. I really don't think though testing w/ the FAS-DPD is necessary everyday or every other day. But, I would like to see what others do as far as the frequency of chlorine testing with the FAS-DPD, especially those who don't have a SWG. What do you do Mark/how frequent?
At that water temp and cya level, I am surprised you can go 3 days without adding CL.

I only test the CYA 1x/mo. Not sure if I should test more. I didn't think CYA gets consumed but it appears differently. Now this makes me wonder if I should raise it back to 50 like it was last summer, or 40 as it was before testing it today.

 

[bbrock]

Well, if you want to prove/disprove anything growing in the water take the FC up to 8ish at sunset. Let the pump run to circulate the water 30-60 minutes and take a chlorine reading after the sun is off the water. Take another before the sun is on the pool in the AM to prove if anything organic inthe water is consuming the chlorine.

Overnight FC Loss Test (OCLT)

My pool will be in shade by 1800. I can then test and add enough chlorine to bring to the upper range of my FC based on a CYA 30. But, do you think I should bring my pH to 7.0 or 7.2 (based on what I read at the SLAM and OCLT). I usually lower my pH to 7.4 and let it climb to 7.6 to keep it balanced for my pool based on Pool Math. Lowering it to 7.0 may lower my TA, right?

 

[pooldv]

Agreed that chem geek's input to TFP is invaluable. If he said not to swim in a pool with FC of 10 I would expect it is because there was 20 or less CYA. There are myriad posts here stating that it is safe to swim up to shock level for your CYA level.

Here are a few,
Safe to swim at Shock level?
Effects of high CYA on chlorine demand
Trying to interpret chlorine/CYA relationship article

He will probably be along to expand on it here.

But, if you don't want to swim then that is totally fine. We spend a lot more time here telling people not to swim than vice versa.

 

[cowboycasey]

Tx for the reply. I never have used the target chlorine off the Chlorine CYA chart, rather just adding to high range for my CYA based on Pool Math. I know the target chlorine is the midpt between in the FC range, but is that really important? I thought it was more important to keep it above minimum.

As for the swimming in FC of 25 or >10, I have read otherwise. Again, to refer to stuff read by the wise Chem Geek, it is not advisable to swim until the FC drops to below 10. Don't ask me exactly why, but he laid out a good reasoning for it. I have 2 year old twins, so I would rather error on the side of caution and keep them out until the FC is at a safe level to swim. If that means 10, and a period of not using, then that is how it has to be. It just sucks knowing that it is warm air temps, my water is nice and warm and, and I am going to have to stay out of it until all this is over.

I believe the FC over 10 has to do with PH, I have never read or seen anything about not using pool when fc is over 10.. it have seen over many posts you can swim in anything under your SLAM level tied to your CYA level.. At your CYA level of 30 you could swim all the way up to fc of 12...

With that said, this has nothing to do with your cloudy water.. The only thing I see is your high CH level, could that be something causing the cloudiness? would a PH of 7.4 and high CH cause something? I am just throwing things out there and see Maybe @chem_geek will know

 

[chem geek]

I don't believe I ever said one cannot swim unless the FC is below 10, at least not generally without talking about a specific CYA level. The general rule is that it is safe to swim if under the SLAM level (FC/CYA ratio of 40%). Technically, the SLAM level has the same active chlorine (hypochlorous acid) level as 0.6 ppm FC with no CYA so less than commercial/public pools that don't have CYA (such as most commercial/public indoor pools and all such pools in New York state).

In this particular case with the numbers posted in the first post of this thread, you can put those numbers into PoolMath you will find that the CSI is +0.24. That normally would not be creating scale since we usually only see that at around +0.7 or higher in pools though we have seen it in spas at around +0.3 or so. You said you let the pH creep up to 7.6 so if that happened then the CSI would be +0.44. Since the CH is so high it is possible for the cloudiness to be calcium carbonate. If you lower the pH and the cloudiness dissipates/clears, then it's likely to have been calcium carbonate. If not, then it might be algae though that should not grow unless the FC got a lot lower (or some measurements are wrong or circulation very poor in some area).

Losing 1 ppm FC per day at 91ºF with a pool cover is not abnormal. Chlorine oxidizes pool covers so even if the pool cover were opaque to UV (which it may not be if it's a clear or partially clear cover) so that you didn't lose anything from sunlight, you'd still have chlorine demand from oxidizing the cover. That happens in my pool at 88ºF at around 0.7 ppm FC per day if the pool is not used.

 

[bbrock]

Tx pooldv, comboycasey, & Chem Geek for those last few posts. @Chem
geek, sorry I must have overlooked that the safe swimming thing with a FC 10 was probably related to a low CYA or either I got it confused with a bromine spa where that wad recommended.

Do u all think I should try lowering the pH first to see if that clears it, or do the OCLT? Not sure if I should do one at a time so as to isolate and identify the problem.