Pool Not Holding Free Chlorine

[NewNatatorium]

Hello- I need some help figuring out why my pool is not holding free chlorine. It is an indoor pool and is not being used. We just bought the place and I'm learning how to test and balance everything myself. Per advice from the good folks on this forum, I shocked the pool and kept it there (FC at 12, CYA30) for 30 hours (CC was at 0.5 or 0 the whole time). The CH was very low so we added about 25 pounds of Calcium Chloride on Saturday (from the pool store) to raise the level. On Sunday, the FC read 0.5 and CC was 0.5. I added enough 10% pure chlorine from the pool store to raise the FC to 5-6. I want to keep it at 5-6 since we aren't using it and I don't want to add chlorine every day. I wasn't home to test the water all day. Tested this morning, Monday, and the numbers didn't change at all. I searched the forum and everything says that adding Calcium shouldn't effect FC levels, however, that is the only thing that was done differently. I want to get this thing balanced and get the right amount of chlorine in it so I can put the cover back on and turn the heat off. This pool is costing us money to heat the room to keep condensation down and we aren't even using it! Please advise on how to get it to hold the FC. The water is crystal clear.

FC 1
CC 0.5
pH 7.4
TA 100
CH 270
CYA 30

 

[Sid/]

Just curious of what test kit you are using?

 

[NewNatatorium]

Just curious of what test kit you are using?

Sorry, I keep forgetting to put that in my signature. It’s the Taylor K-2006 (FAS-DPD) compete kit.

 

[ping]

To get rid of excess chlorine demand we follow a process known as SLAM. You mentioned that you shocked the pool for 30 hours but that did not tell me that you followed our SLAM method, see my signature for links.

There are two things that consume chorine, they are organics and sunlight. If the indoor pool has a high chlorine demand then I would say there is an excess of organics in the pool that must be killed off with chlorine. You mention CC's, that is only part of the equation and a lot of pools don't have any CC's even though there are organics.

How much chlorine does the pool lose overnight?

 

[Rollercoastr]

For a while there I was wondering if your filter had an issue, but losing chlorine and that pesky dead algae you keep finding make sense. You're not done with your SLAM yet.

When all the algae has been eradicated, your pool will consume chlorine very slowly! If you want to save some energy, go ahead and cover it back up for a while. Breathing is good, but .5 CC isn't a crisis.

 

[NewNatatorium]

To get rid of excess chlorine demand we follow a process known as SLAM. You mentioned that you shocked the pool for 30 hours but that did not tell me that you followed our SLAM method, see my signature for links.

There are two things that consume chorine, they are organics and sunlight. If the indoor pool has a high chlorine demand then I would say there is an excess of organics in the pool that must be killed off with chlorine. You mention CC's, that is only part of the equation and a lot of pools don't have any CC's even though there are organics.

How much chlorine does the pool lose overnight?

Sorry I didn’t use the correct wording, I followed the SLAM method as per the good folks on this forum.

I mentioned CC’s because that is how you know you are done slamming. When the FC holds at the given level, the CC is at or below 0.5, and the water is clear. What kind of organics could be in the pool if the water is crystal clear and there is no visible algae anymore?

I was told told (on this forum) that I don’t have to do an overnight chlorine loss test because it is an indoor pool. When I was Slamming, it did not lose any chlorine from one day to the next. It has only lost chlorine since adding the calcium.

Thank you for your help!

- - - Updated - - -

For a while there I was wondering if your filter had an issue, but losing chlorine and that pesky dead algae you keep finding make sense. You're not done with your SLAM yet.

When all the algae has been eradicated, your pool will consume chlorine very slowly! If you want to save some energy, go ahead and cover it back up for a while. Breathing is good, but .5 CC isn't a crisis.

OK. Thanks Rollercoastr! There is no algae anywhere in sight anymore. How long do i keep slamming for? I didn’t think I should cover it while slamming. The cover has been off for over a week and now I’m concerned about it growing algae being that it’s all rolled up.
Thank you for your help again!

 

[mknauss]

Adding the calcium had no effect on the FC in the pool.

Only organics or UV impact the FC.

Do another OCLT. And even though it is indoors, follow the process as shown.

Something is eating the chlorine.

 

[NewNatatorium]

Adding the calcium had no effect on the FC in the pool.

Only organics or UV impact the FC.

Do another OCLT. And even though it is indoors, follow the process as shown.

Something is eating the chlorine.

OK. I had read that about the Calcium, but just can’t seem to figure out what could be in there. I will do an OCLT and post results in the morning.

Thank you!

 

[Rollercoastr]

There is no algae anywhere in sight anymore. How long do i keep slamming for? I didn’t think I should cover it while slamming. The cover has been off for over a week and now I’m concerned about it growing algae being that it’s all rolled up.
Thank you for your help again!

Think of the SLAM like a prescription for antibiotics, because well, it is...! You have to complete the process even though it seems like you're done. Really the only indoor curveball is CC - that measure will linger. The OCLT is designed for outdoor pools, but the theory still applies.

Holding chlorine is the criteria to focus on now. When the SLAM is actually finished, you'll see the consumption of FC plummet to almost none. That you're seeing any consumption now is significant, and you're seeing a lot!

If you're careful to not exceed the SLAM range of FC, it won't be high enough to damage your cover or other equipment. CC might spike, but until it does, you could save some energy and peace of mind by covering the pool. FWIW, I haven't been kind to my cover, yet it's been forgiving. It spent the past off season rolled-up on the garage floor! Even if yours becomes home to algae, I would think the surface area of the cover is so small compared to the volume of your pool that it would clean up quickly and easily.

 

[NewNatatorium]

Think of the SLAM like a prescription for antibiotics, because well, it is...! You have to complete the process even though it seems like you're done. Really the only indoor curveball is CC - that measure will linger. The OCLT is designed for outdoor pools, but the theory still applies.

Holding chlorine is the criteria to focus on now. When the SLAM is actually finished, you'll see the consumption of FC plummet to almost none. That you're seeing any consumption now is significant, and you're seeing a lot!

If you're careful to not exceed the SLAM range of FC, it won't be high enough to damage your cover or other equipment. CC might spike, but until it does, you could save some energy and peace of mind by covering the pool. FWIW, I haven't been kind to my cover, yet it's been forgiving. It spent the past off season rolled-up on the garage floor! Even if yours becomes home to algae, I would think the surface area of the cover is so small compared to the volume of your pool that it would clean up quickly and easily.

Hi Rollercoastr-
I will get those FC numbers back up and continue the SLAM and leave it there for a number of days. Only got it up to five yesterday because I needed more chlorine and the store is 45 minutes away.

It must be consuming something because I can smell the chloramines sometimes when i go in there (but not all the time which is weird to me). The black dot for my CYA never completely disappeared whenever i was first reading it, and we estimate up so we estimated 30. It is less than that now as I can still see the dot pretty good at 30.

That is super great to know about the cover! You must not have mice in your area. I don’t think we could leave ours on the garage floor. Country living at its finest!

Thank you so much for the advice.

- - - Updated - - -

Here are the OCLT results:

last night:
FC 5
CC 0

this morning:
FC 5
CC 0.5 or less (barely turned pink)

all other numbers stayed the same. CYA seems to be below 30 now because the dot is easier for me to see than before.

 

[Rollercoastr]

Maintaining the FC overnight is passing the OCLT. That's good news, particularly when we consider that the pool consumed 11ppm between your test on Saturday and yesterday!

It must be consuming something because I can smell the chloramines sometimes when i go in there (but not all the time which is weird to me).

This is another indoor pool thing: I'd edit that statement to say "it must've consumed something..." The CC you smell has likely been building since you started this process. I've experienced the same coming/going of CC odor detection - I can't explain that either, but you're not alone. Just recently I noticed when I swam underwater, I could smell CC for a moment when I resurfaced. That was the only time it happened though, and no-one noticed it...

Under normal circumstances, CYA degrades very slowly. I'm tempted to chalk that difference up to relatively subjective test.

Mice! I didn't even think of that! I got lucky - I even brought the cover inside around the time that mice start to seek the warmth/shelter of the garage.

 

[NewNatatorium]

Maintaining the FC overnight is passing the OCLT. That's good news, particularly when we consider that the pool consumed 11ppm between your test on Saturday and yesterday!



This is another indoor pool thing: I'd edit that statement to say "it must've consumed something..." The CC you smell has likely been building since you started this process. I've experienced the same coming/going of CC odor detection - I can't explain that either, but you're not alone. Just recently I noticed when I swam underwater, I could smell CC for a moment when I resurfaced. That was the only time it happened though, and no-one noticed it...

Under normal circumstances, CYA degrades very slowly. I'm tempted to chalk that difference up to relatively subjective test.

Mice! I didn't even think of that! I got lucky - I even brought the cover inside around the time that mice start to seek the warmth/shelter of the garage.

Yes I couldn’t believe it had consumed that much since it had been holding. I haven’t added any more chlorine yet (had to actually get some stuff done today besides mess with pool). I put the cover on today too so I hope it still reads good in the morning.

The statement about consumed instead of is consuming does make more sense and helps me understand the consumption process better. Do you have a lot of windows around your pool or skylights? Do you swim every day? Just curious how people use their pools.

I only know about the mice because I have a friend that had a pool that she takes down and puts back up each year. She had it stored in their storage shed, inside it’s cover, off the ground, and the mice somehow climbed up there and chewed holes in it that it ruined the whole thing!

 

[Rollercoastr]

Do you have a lot of windows around your pool or skylights? Do you swim every day? Just curious how people use their pools.

My natatorium is open to the rest of the house, so it gets light from the house in general as well as skylights, windows and a doorwall. Even so, I tend to swim in the evening as I don't spend many wkds at home. I mentioned smart LED bulbs in your other thread. I have them throughout the house, but not in the pool roo... natatorium. I have 4 cans above the pool that house halogen floodlights. I really want to update them, but as you know it's a daunting project. I'm not sure I want the answer to the question: how many people does it take to change a lightbulb above a pool?

When the pool is warm, I try to use it everyday. I had 6 guests last night, so I had the water a 90º and everyone had a great time. I shut the heater off when they left because I'll be traveling etc for a while. If CC's are above .5, I'll also use the opportunity of the cooler water to pull the cover off.

Here's a daytime pic (Christmas Day a year ago):

Evening shot:

 

[NewNatatorium]

Wow, Rollercoastr! Your natatorium is amazing! Thanks for sharing the pictures. I see why it gets used so much being that it is the center of attention in your house. We are about to find out how many people it takes to change those lightbulbs. We have a friend that has some scaffolding planks that he thinks will work if we just put a tall ladder on it. Now we just need to find a weekend without basketball to give it a try. I will let you know how it goes.

The FC in our pool has been holding at six for the last 8 days I think it is and there are no floaties on the bottom of the pool. I'm now checking it every other day. I hope we can save enough money to buy a heat pump this spring so we can start using it every day like you!

Enjoy your travels and thanks again for the pictures.

 

[NewNatatorium]

Rollercoastr- We used two 24’ foot planks we borrowed from a contractor friend. My husband said united rentals had either sixteen or twenty foot planks we could have rented, but we needed at least twenty-two feet in length. This actually turned out to be one of the easier projects we’ve tackled since moving!