Chlorinator cant keep up

[uzun]

I have had a 15,000 gallon swimming pool running with a Pentair IC40 Chlorinator for about 3 years now. The pool is solar heated in the southern california area, and is covered most of the time in a rural area. For the first 2.5 years or so I would keep the cell at about 40% and it would keep the chlorine level around 2PPM or so. For the past 6 months, I keep it at 100%, and I have to add chlorine.

I thought perhaps the cell was getting old so I replaced it, same thing. It can no longer keep up with the pool. When I test the chlorine levels out of the jets, its very high, like > 5ppm. The chlorinator cant seem to get the pool much over 1.5ppm or so regardless of how long I run it. It's clearly producing chlorine though because the chlorine readings directly from the jets are MUCH higher than those in the pool.

The water is clear, there are no stains or algae. I have tested the water myself and at several local stores, there seems to be nothing wrong with it. No nitrates or phosphates to speak of, high CYA level of 50-80, ph is normal, salt levels fine, no one can find anything wrong. It's fairly hard water but no different than it ever was. The pool is generally warm, like 90 degrees but its always been that way most of the year, even before this trouble.

All the indicator lights on the IC40 indicate everything is fine, and this is a new cell, it's not clogged or anything. Cleaning it had no effect (I did clean it even though it didnt appear to need it).

If I run the system even 12 hours a day I cant get the chlorine levels in the pool to raise much above 0.5 to 1.5ppm regardless. I have shocked the pool, no lasting effect. The chlorine just seems to go away somehow and I cant figure out why.

For now I just add a couple of cups of liquid chlorine every 3 days or so to keep the chlorine levels above 1. But I shouldnt have to do this, I never had to before.

What could have changed? The chemistry seems fine, no one can find anything wrong, and I cant think of anything thats changed.

-Roger

 

[jblizzle]

Welcome to TFP!!!

What is your actual CYA? 50-80 is a ridiculously large range.
What kit are you using to test your water?

I think you may have 2 problems:
1. If the CYA is 50, that is too low and the SWG will not be able to overcome the FC loss to the sun
2. Your FC levels way too low and now likely have something growing in water also consuming the FC faster than the SWG can make it. (Generally SWG are good at maintaining FC, but really raising it very fast)

I would suggest raising the FC up toward shock level with bleach (pool-school/chlorine_cya_chart_shock) and then performing the OCLT (pool-school/overnight_fc_test) to see if anything is in the water. If you fail, then it is time to go through the shock PROCESS (pool-school/shocking_your_pool).

You will need the FAS-DPD chlorine test to do this correctly.

 

[uzun]

CYA level is currently 75, it has been in the 50 range most of the time. This appears to make no difference at all, at 75 I am seeing the same thing I saw at 50. I have shocked the pool using chlorine shock as well as oxidizing shock in the past few months, this has no lasting effect. I test for free chlorine, there is little or no combined chlorine ever on any tests. Both my tests and the tests at the stores confirm there is little or no combined chlorine present in the pool. I have the taylor k-2006 FAS DPD kit I can test with tonight.

Should I add chlorine to raise the FC level to something like 4 tonight, then see what it is in the morning? I bet its still close to 4. When I add liquid chlorine it appears to stay stable for about 48 hours or so before dissipating again. It's just that the chlorine from the generator seems to go away fast.

I will try this tonight, I will try and get home early, run the filter, get the chlorine level to something around 4 using liquid, make sure its stable at that level, then test it first thing in the morning and note the difference.

I have shocked the pool more than once in the past couple of months, this has no lasting effect. Oxidizing shock does nothing really, and the chlorine shock raises the FC levels for a few days then its back to business as usual.

-Roger

 

[jblizzle]

The shock level for you CYA of 75ppm is a FC of 30ppm. I would turn off the SWG, leave the pump running, raise the FC up to at least 20ppm, test after dark, then test in the morning again before the sun comes up.

My guess is your idea of "shocking" the pool is vastly different than what we recommend which is a continuous PROCESS and not a one time addition of chlorine.

Read the links I provided and the rest of Pool School.

 

[alanpaul]

Uzun,
I'd trust JBlizzle. It probably is something growing in the pool, as he surmised.
And, of course, the concept of Shocking the Pool to kill algae is very different than you might think.
[See Pool School, above.]
Pool shock products are a tiny bump-up for post-bather use, not for clearing up a chemical or organic issue.

Yet I wonder, could it be that the SWG control board isn't working, and is giving a false impression of chlorinating at 100%? I don't know enough to tell you how to check the circuit board, but I thought I'd mention this, as I know someone who experienced this problem with his SWG.
Alan

 

[Richard320]

The problem is likely that you are shocking your pool the pool store way - which is justa one-time blast of chlorine.

Around here, shock is a process.

Shut off the SWG, raise FC to a respectably high number, something like 10, using bleach. Verify the level using the FAS-DPD test using a 25 ml sample after the sun goes down. Leave the pump running. In the morning, check it again using the FAS-DPD tester and 25 ml sample. If you lost more than 1.0, you need the shock process.

Only two things can consume chlorine: sunlight, and organics. You've just ruled out sunlight by doing it overnight.

 

[uzun]

I have been shocking the pool the "pool store" way. I add 2 pounds of a Calcium Hypochlorite shocking powder, and wait for it to go back down. This takes like a day or so.

Right now FC is 0.5ppm or lower already. I test this every day

Right now the water is very clear.

The only thing I do not know is how much free chlorine I would lose if I rose it up to say 10, using liquid chlorine and then tested it the next morning. I hate to do it because I use the pool every day. But I see that's probably the best thing.

So tonight I will do the following-
1) Turn off the SWG
2) run the pump continuously
3) raise the FC level to 10 using liquid chlorine as measured using a 25ml sample size using the Taylor FAS-DPD titrating test.
4) check tomorrow morning to see what the FC level is, and make sure the water is clear and combined chlorine is still 0.5ppm or less

Does this sound correct?

 

[jblizzle]

Pretty close.
3a) Add enough bleach to target 10ppm (using poolcalculator.com to determine how much)
3b) After an hour (and it is dark), test the FC

BTW, it is generally safe to swim in a pool with the FC up to shock level. For you, it would be safe up to a FC of 30ppm ... and that would STILL be less active chlorine than you would encounter in a public pool with 0 CYA and a FC of 2ppm.

 

[Richard320]

I have been shocking the pool the "pool store" way. I add 2 pounds of a Calcium Hypochlorite shocking powder, and wait for it to go back down. This takes like a day or so.

Right now FC is 0.5ppm or lower already. I test this every day

Right now the water is very clear.

The only thing I do not know is how much free chlorine I would lose if I rose it up to say 10, using liquid chlorine and then tested it the next morning. I hate to do it because I use the pool every day. But I see that's probably the best thing.

So tonight I will do the following-
1) Turn off the SWG
2) run the pump continuously
3) raise the FC level to 10 using liquid chlorine as measured using a 25ml sample size using the Taylor FAS-DPD titrating test.
4) check tomorrow morning to see what the FC level is, and make sure the water is clear and combined chlorine is still 0.5ppm or less

Does this sound correct?

Almost. On 3) add enough to get it to 10, but don't assume it's exactly 10. Let it mix for half an hour, maybe brush a few times to really get it well-dispersed. Then test and record it. It could be 9.6, could be 10.4. We don't care, as long as it's in the neighborhood and it's accurate. As an aside, it's safe to swim up to shock level. Just take your last reading after everyone's out of the pool awhile.

Step 4) Check FC and CC and clarity. If you lost more than 1.0 FC overnight, or if CC is greater than .5 or ifthe water is still cloudy, you need to raise FC up to 30, and keep retesting and adding more bleach to keep it at 30 until it passes the three tests. That is the shock process. Beat the algae down brutally and keep kicking it while it's down until it's all dead. The pool store way is just knocking it down for a few hours or days. It keeps getting back up.

You can run your SWG during the day to help maintain the FC level that high. Make sure it's off overnight when you do the loss test, and don't run it on boost or you'll burn it out.

 

[woodyp]

To ease your fears, you can safely swim in water up to your shock level per your cya level.....and 10 ain't even close! I raise mine to 8 or so every day with my CYA at 50---------and lose about 3.5 to 4 ppm daily.

 

[uzun]

So when you say "Bleach" you mean any sort of chlorinating agent. I have some liquid chlorine and calcium Hypo based shock powders at my house now. Is using the calcium hypo to get around 10ppm ok? I notice that stuff seems to dissipate quick once it starts to go.

Its easier for me to use calcium hypo based shocking agent right now.

 

[jblizzle]

Anything to get the FC level up ... although are you sure you are not raising your calcium too high by continually using cal-hypo?

That is why we recommend liquid chlorine (bleach) ... there are no negative side-effects.

 

[Richard320]

So when you say "Bleach" you mean any sort of chlorinating agent. I have some liquid chlorine and calcium Hypo based shock powders at my house now. Is using the calcium hypo to get around 10ppm ok? I notice that stuff seems to dissipate quick once it starts to go.

Its easier for me to use calcium hypo based shocking agent right now.

You can...we don't recommend it usually. Cal-hypo adds Calcium to the pool, and in California, you probably have more than enough already.

I didn't see a CH reading. Did I miss it? Do you have any sign of scale? Rough spots, or discolored patches where it looks like the pool walls have psoriasis?

 

[uzun]

I shut off the SWG, turned on the pump, added about 1.5 gal of liquid chlorine. I've been testing the water every half hour or so, but it continues to rise. I am waiting for it to level off. Right now it tests 16.4 FC, 0.2 CC.

There hasnt ever been much Combined Chlorine in the past, in any of my tests or the stores. The water has always been crystal clear, its never gotten cloudy and I've never seen any algae anywhere.

Once it reads the same twice I'll note it and compare it again in approx 12 hours.

-Roger

 

[jblizzle]

You need to test it again before the sun comes up. The idea is to eliminate the sun as a FC reduction source.

 

[uzun]

I added the liquid chlorine to the pool around 7PM. The FC values rose for a while, then started to fall. At midnight the FC reading was 13.2, with 0.4 Combined Chlorine. At 5AM the free chlorine was 11.4 with a combined chlorine reading of 0.4.

So the FC reading started to fall pretty rapidly once the chlorine got mixed up it would seem, assuming 5 hours was enough time to mix up the chlorine evenly (the pump ran from 7PM to 5:30AM with the SWG off).

What do I do now? It would appear the chlorine is being eaten up by something organic in the pool.

I should repeat there is no algae in the pool and the water is completely clear. When its even a bit cloudy I can see it when I am swimming with my goggles on. The shock process directions talk about algae and clearing water, whatever is eating the chlorine in my pool is not visible. I see no cloudiness or signs of any algae anywhere.

To shock this pool according to your shock process link, I would need about 5 gallons or so of Chlorine (15000 gallon pool). Get the chlorine levels to 30, take a reading every few hours and keep it at 30. Run the pump continuously while keeping the FC level at 30 until it stays at 30 on its own overnight. Once I do this will the pool be back to normal, and I wont have so much trouble with the chlorinator not keeping up with the demand anymore (even when it falls back down to the normal level of 3 or so, it will be easily able to keep the pool at 3, like it used to be able to do?).

-Roger

 

[ping]

Your situation is the exact same situation I had 2 years ago, the water was clear, no visible signs of algae, no CCs, but the SWG just could not make enough chlorine. I bought the correct test kit and ran the OCLT and found out it was consuming the chlorine at night time just like your pool is. It actually took my pool 5 days of following the shock process before it held chlorine overnight.

Maintain the pool at shock level 30 ppm until it passes the OCLT and brush the pool as much as you can to scrub the surface clean. After a while you might just see a bit more sparkle in the water.

After you pass the OCLT, let the FC drop and then maintain according to this chart, pool-school/chlorine_cya_chart_shock. I suggest to read as much as you can in Pool School, the large button on the top right of each page, and you will learn more about taking care of a pool than most pool store employees will ever know.

 

[Richard320]

I added the liquid chlorine to the pool around 7PM. The FC values rose for a while, then started to fall. At midnight the FC reading was 13.2, with 0.4 Combined Chlorine. At 5AM the free chlorine was 11.4 with a combined chlorine reading of 0.4.

So the FC reading started to fall pretty rapidly once the chlorine got mixed up it would seem, assuming 5 hours was enough time to mix up the chlorine evenly (the pump ran from 7PM to 5:30AM with the SWG off).

What do I do now? It would appear the chlorine is being eaten up by something organic in the pool.

I should repeat there is no algae in the pool and the water is completely clear. When its even a bit cloudy I can see it when I am swimming with my goggles on. The shock process directions talk about algae and clearing water, whatever is eating the chlorine in my pool is not visible. I see no cloudiness or signs of any algae anywhere.

To shock this pool according to your shock process link, I would need about 5 gallons or so of Chlorine (15000 gallon pool). Get the chlorine levels to 30, take a reading every few hours and keep it at 30. Run the pump continuously while keeping the FC level at 30 until it stays at 30 on its own overnight. Once I do this will the pool be back to normal, and I wont have so much trouble with the chlorinator not keeping up with the demand anymore (even when it falls back down to the normal level of 3 or so, it will be easily able to keep the pool at 3, like it used to be able to do?).

-Roger

There IS algae in your pool. The overnight test proved it!

Individually, they're microscopic and you need quite a lot to tint the water or make it look cloudy.

You have summarized it correctly. Beat it down with a high dose of chlorine and keep kicking it while it's down until it's all dead. Some of the most prolonged battles we've seen here have been from algae hiding inside ladders, beneath rungs, and inside the light housing. You might need to pull things apart and do some scrubbing.

 

[uzun]

I raised the FCL to 30 at 7AM friday morning. I kept it at 30 all day, and it was 30 at 9PM friday night. Saturday morning at 5AM FCL is at 26.5 So I guess i have a ways to go, this is going to really use a lot of electricity. At least I found someone who has had this same problem (ping). I really thought I was going crazy for a while talking to my pool guy and the pool store employees who told me its just a mystery. I really hope this works, it seems logical.

I filled the pool with new water about 3 years ago or so, and I never shocked it once until about 6 months ago (when I started to use the oxidizing shock and some chlorine shock pool products, just dumping them in and never measuring anything). It seemed to just slowly creep up the SWG requirements over the years until the SWG could no longer keep up even at 100%.

Maybe tonight will be the night it holds the FCL at 30.

-Roger

 

[uzun]

The pool has gotten very hot now, the pool water is well over 95 degrees right now. I am about 20 miles inland in San Diego. It's been very sunny and warm both today and yesterday, normally I would not run the solar panels more than once a week this time of year. I want to circulate the shock water through the solar panels though. Yesterday I ran water through the panels about 10 hours, and today about 8 hours, but right now the water is just getting too hot and I always heard hot water breaks down chlorine.

Is the extreme heat going to affect shocking of this pool? I turned off the solar for now, I cant see how having the pool get over 100 degrees is a good idea regardless.

(I have one of the automatic panels that prevents the pool from opening up the solar when the panels are cooler than the pool water, so unless I mess with the thermometer calibration settings the pool will never send water to the solar panels at night, the pool water is too warm and the panels cool off too much at night).

-Roger