Really difficult pool...

[TreeFiter]

I have a pool that has been extremely difficult all season. Initially one of the other guys at my company was working on this pool. It was green when we started. After a month, it was still green. At that point it was given to me to figure out. I shocked the pool hard (12lb of trichlor) and kept as much chlorine flowing into the pool as I could. I completely filled the automatic chlorinator, and I put two floaters in the pool. I was using about 20 tablets/week. The pool went from green to a nice cloudy blue overnight, and within two weeks had cleared up.

Now that the pool had cleared up, I cut back on the chlorine in a big way. I took out the two floaters, and I cut back the chlorinator too. I left it running a bit high thinking that I can always turn down the chlorinator more next week, rather than turn it down too much now and have it turn green again. This was all happening during the hottest week we've had all summer (high 90s). So I had to guess how much would be enough. I was pretty close. The pool made it 6 days. When I got there on day 7 it had clouded up again. I spoke to the owner, and she said she was in it the night before and it was crystal clear. When I tested the water, there was still a reasonable amount of chlorine in the pool (probably around 5ppm). So I've been fighting with it ever since.

I raised the chlorine way up using the chlorinator and the floaters. After about a week, it was almost clear. I could see the Main Drains in the bottom. After a second week, it is cloudy again. Yesterday, when I was there, I tested the water and the FC was over 20. The filter was replaced earlier this season, and is producing a good cloudy backwash every week. The pool was treated for phosphates about two weeks ago (I know how you all feel about phosphate treatments, but it rules out phosphates as a contributing factor).

As of yesterday:
FC=22
CC=0
pH=7.2
TA=80
CH=50
CYA=100
Fiberglass Pool, Sand Filter, using 7day Tablets. Running 24/7, and serviced at least once a week.

Does anyone have any idea what is going on here? Apparently this pool has been difficult for years, and that is why they fired the last guy who took care of the pool and came to the company I work for. He never figured it out, and he didn't seem to come up with anything to even try (like replacing the filter). What could be making this pool so difficult?

 

[chiefwej]

The CYA is too high. You are reporting a CYA of 100 which is the upper limit of the tests, so it could be much more than that. The only way to get it down is by draining part of the water. You can do another test using half and half pool and tap water then double your result. That will give you a closer approximation of the true level, so you can determine how much water needs to be drained.

 

[JasonLion]

The problem is almost certainly high CYA. Your use of trichlor means the CYA level has been going up rapidly, and was probably too high to begin with. CYA at 100 means the CYA could actually be much higher. The common CYA test will report any CYA level over 100 as 100. Maintaining a pool with CYA at 100+ is nearly impossible. You need to get CYA down below 100 before continuing and stop using forms of chlorine that are constantly adding more CYA.

 

[TreeFiter]

Thank you Jason. I suspected that the high CYA might have something to do with it, but with FC at 22, I thought it should still work. I didn't realize that the test pretty much tops out at 100.

I think the problem really came from the the tech before me not shocking hard enough. For weeks, he would put 4lbs of trichlor in the pool and get no result. The following week, he would do the same, over and over again. Somehow he never figured out that if 4lbs didn't work, he should try hitting it harder. So in the span of a month or so, this pool saw about 20lbs of trichlor that had no effect on clearing it up. Then it got 12 more which did the trick, but by then the CYA levels were too high.

Does Dichlor raise CYA levels? That is pretty much the only other chlorine I have readily available to me.

I'm thinking liquid chlorine might be the way to go, but how can I manage the levels on a weekly service schedule without a liquid chlorinator?

Any suggestions how to manage this pool without having to do anything too drastic/expensive?

Keep in mind my boss already sold her a filter she probably didn't need, and over a month of service calls where our techs didn't really do anything but waste chemicals. I really don't want to see this customer get slammed again with a big bill to straighten it all out. I need to come up with something to help this lady out.

 

[ping]

Dichlor will raise the CYA faster than trichlor.

Run a CYA test with half pool water and half tap water for the sample and multiply your result by 2. If the CYA is near 100 the test should read 50 with this method. It will give you an idea of how much water needs to be drained.

Draining enough water to lower the CYA to 50 and then start using liquid to chlorinate is the ideal situation. From then on, raise it to shock level each trip. See if the owner is willing to add some liquid chlorine during the week. My in-laws do this with their service.

 

[zea3]

Right now your only viable option is to drain the pool. How much the pool will need to be drained depends on how high the CYA really is. Once the CYA is in the 30-50 range you should use liquid chlorine as the main chlorine source. You could explore the possibility of installing a Liquidator or a Stenner pump to deliver liquid chlorine between visits. You could also check into adding a Saltwater Chlorine Generator system to the pool.

 

[TreeFiter]

Switching to liquid chlorine won't be a good option for the situation, because my company doesn't use it. We would have to buy it just for this one pool. SWG is a good option, and I've suggested it to the customer already. Shes not ready to put that much money into the pool this year. She already bought a new filter, and has had quite the bill for service calls and chemicals.

I'd have to drain about 40% of the water out of her pool. That means she will need to replace about 15,000 gallons of water. Thats not going to be cheap.

I'm still a little bit confused though. Going back to Jason's post, I have determined that the CYA=100 through dilution. If we keep FC at 5-7% of the CYA level, that would mean that if I kept the FC at 7, the pool shouldn't cloud up, and if I remember correctly, 10% would be shock levels so that 10ppm would bring it back. This pool tested at 22 ppm for FC. Am I missing something?

 

[chem geek]

As for the clouding up, you initially said the pool was at 5 ppm FC when that happened and that makes sense given the 100 ppm CYA. The second time you raised the chlorinator way up, that added Trichlor so both FC and CYA, and the pool clouded up in the second week when the FC was 22 ppm. That is strange and probably not algae -- more likely a filtration problem after something got into the pool. There are over 100 Reasons for Cloudy Swimming Pool Water. Could the owner have added some chemical to the pool? Some are incompatible -- some polymeric metal sequestrants are completely incompatible with polymeric clarifiers and produce a precipitated mess. Also, phosphate removers that don't have clarifiers can also cloud the water with lanthanum carbonate. Did you use an additional phosphate remover during that time?

The following are chemical facts independent of concentration of product or of pool size:

For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm.

So yes, Dichlor increases CYA and does so even faster than Trichlor. There is no mystery here. You are using stabilized chlorine products in these pools, the CYA level is rising, and the FC isn't being raised proportionately so algae starts to grow either clouding a pool or looking like mysterious chlorine demand in an SWG pool. Even if algae isn't growing, the low FC/CYA ratio has oxidation be much slower so bather load contaminants take longer to oxidize and if they build up could also cloud the pool (though usually if it's something cloudy and not growing, it can be filtered out unless the particles are very small).

As for what you can do, you can probably do a hybrid approach of using chlorinating liquid to raise the FC to a higher level weekly, Trichlor to maintain some chlorine in the pool during the week (but not as much Trichlor as has been done in the past when it was the only chlorine source), and some periodic water dilution when the CYA gets too high. With the weekly bump in chlorine, the FC level could get down to around 5% of the CYA level and probably still be OK, but that means adding chlorine to get to a much higher level so that you end up there -- perhaps 15% of the CYA level though it depends on the CYA level. If you need to use an algaecide for insurance, you could add Polyquat 60 weekly or use 50 ppm Borates (some pool services use copper sulfate, but that's risky in terms of pool staining and turning blond hair green). I know that with Polyquat 60 weekly, green algae didn't start to grow even with lots of phosphates (3000 ppb) until the FC was around 2% of the CYA level so Polyquat can be effective (at extra cost, of course).

 

[TreeFiter]

Thanks chem geek. This information is extremely helpful. I'm starting to put together some cheat sheets for some of this stuff, so I can look it up in the field.

Algaecide is a great idea. I hardly use it on a regular basis, so it didn't even occur to me. I think that will be the first thing I try. Its readily available, and not too expensive. If liquid chlorine were readily available, I'd try it, but I would have to convince my boss of a lot of things.

I'm going to start vacuuming this pool on waste every week so that there is a need to replace water a little bit at a time.

 

[chem geek]

Also, when you have pools you need to shock and if your boss doesn't want you to use chlorinating liquid, see if he'll go for Cal-Hypo. You just have to be careful not to use it too frequently or in already hard water pools as it increases CH so can cause scaling and cloudiness of its own.

One pool service in our area uses Trichlor during the week and chlorinating liquid when they visit weekly. They target 4.5 ppm FC and when the CYA gets above 100 ppm they do a partial drain/refill to lower it. This works in most of the 2000 pools they service. For those that don't (mostly because their lowest FC during the week isn't enough to prevent algae), they use phosphate removers, but that's only with a handful of pools. We have 400 ppb phosphates in our fill water so it would get expensive for them to use a phosphate remover in all pools. And as you've found out, even a phosphate remover does not guarantee no problems.

If you can afford the weekly Polyquat 60 approach, then you'll probably be able to get away with up to 200 ppm CYA if you keep the FC from getting lower than around 3.5% of the CYA level or roughly half the minimum in the chlorine/CYA chart. The main risk with the high CYA is if anything does go wrong since it will take an extraordinary amount of chlorine to fix the problem, but at least with the algaecide any algae growth even with no chlorine in the water will be slower so more likely for you to be able to catch it and kill it using a lower shock FC level than those that use no algaecide.

 

[TreeFiter]

That all sounds reasonable. I typically aim for around 5ppm in my pools so that I have a little room for chlorine to drop without turning my pools green. Works pretty well in most situations.

I would love to start using liquid chlorine for shock treatments and the occasional boost. For some reason, my boss doesn't want to deal with it. He wants to do things his way, which is seldom the right way in my opinion. That is why I come to this forum. I want to learn whatever I can so that I can hopefully figure out what the right way is in a given situation. I've come a long way in a short time.

Thank you all for your help.

 

[jblizzle]

Seems like all your posts are similar ... green pools, massive use of Trichlor and Dichlor. Until your company switches some part of their procedures, this is going to be a recurring theme. Clearly what you guys do is not what this forum recommends for the private homeowners which are the major focus.

 

[TreeFiter]

jbizzle, its not really fair to say that all my posts are similar...just about every post on this forum involves a pool that is either cloudy or green. I can't imagine too many people are puzzled about what to do with their well balanced sparkling clear pools. This is the first post in which the issue was caused by accumulation of CYA due to the use of trichlor. There have been a few about phosphates, some of which were more about understanding their relationship to other things, such as sequestrants. I've had various questions on how sequestrants work, and the best way to use them.

 

[jblizzle]

Ok maybe not all of them, but many:
"stubborn pools..."
"Sudden chlorine drop"
"How fast can algae take over"

There is a trend that the company's methods do not seem to work. I am sure you are still working on understanding, but I think the advice was the same in those 3 and this thread ... better testing is needed and more chlorine is required depending on the CYA levels.

 

[chem geek]

Most posts haven't been about the FC/CYA relationship such as too low an FC, too high a CYA, use of stabilized chlorine, etc. Those that have are highlighted in red below including those where numbers are uncertain due to use of test strips or where the CYA was not measured or where Trichlor was added.

White Crystalline Precipitate
Phosphates and Sequestrants
Phosphates and Sudden Chlorine Drop
Why does pH rise with salt systems?
Metals and Sequestrants
Vacuum Head hard to move along pool bottom (other styles?) - response
Inline filter for Vacuuming
Why would a Hot Tub turn cloudy when I add pH Increaser
How fast can algae take over?
What problems come from high Total Alkalinity
Fizzing Water
pH so low it doesn't want to rise
Black Stains on Liner
Netting and Vaccing
Nature2 and OxyShock
Vaccing through a DE Filter
Sequestrants and Phospahtes...Is there a relationship?
Cloudiness won't go away
Conditioner-Stabilizer granules blowing back into the pool
Low pH after shocking
Stubborn pools not holding Chlorine
What to do while away for a week? - response
Will salt concentrations change output potential of a SWG
Liner intstallation question - inground pool - response
Really difficult pool
Does anyone out there have a Pool Pilog AG SWG? - response
Need "best method" for LEAK-FREE threaded fitting connection - response
pH - response
Flow error when jets are turned on - response

So it is not that most posts are about this issue, but those posts related to cloudy water or algae seem to be related to the combination of not knowing real numbers since not using a good drop-based test kit and having the FC/CYA ratio too low at some point probably due to use of stabilized chlorine products. You may not have control over what your boss lets you use for chlorine in the pools, but you could certainly get a good test kit so that at least you will know what is going on in these pools, especially for the CYA test that is notoriously inaccurate with test strips. It sounded like the TF-100 was going to be ordered, though I'm not clear if it is currently being used as in this thread, is it?

 

[TreeFiter]

Of the posts that chem geek has highlighted, only about three of them are really about FC/CYA relationships.

Cloudiness won't go away...was more about how to identify what is causing the cloudiness, filtration vs. algae growth vs. calcium
Low pH after shocking...was about the effects of trichlor on pH levels

Its a bit of a leap that all of these problems stem from using dichlor and trichlor. Some of the earlier posts were more about too little CYA in pools, resulting in rapid loss of FC. I think it should be just fine to use dichlor and trichlor in a pool that needs CYA. I am not saying that my company does everything right, but I hardly think that using liquid chlorine or a more accurate test kit is going to fix everyting. It might help on some pools, but the vast majority will be just fine using trichlor and dichlor.

To answer chem geek's question about whether or not I purchased a test kit, I did. I have been using it selectively all week. I have been testing pools that behave the way i want them to (maintaining FC levels with SWG set to less than 50%) and also spot checking possible problems. I have found that if you use test strips correctly, you can get pretty good results as compared to TF-100 kit. When dealing with extremes, the TF-100 will give you a far better measurement than the test strips, but for my average pools, I can tell fairly consistently the difference between 20ppm CYA and 50 ppm with test strips. At this point, I just haven't been convinced of the value of an expensive and time consuming method of testing. I realize that I'm working with a limited data set, so I'm going to keep an open mind and continue to use the TF-100 selectively. Maybe in time, I will see the value.

In the case of the pool at the start of this post, the CYA on the test strip read 100ppm. The FC on the test strip read about 15 ppm. All of my results were very close to what I found using the TF-100 with the exception of FC which was actually 22, and CH which appeard to be 100 on the test strips, but was actually 50. I attribute this to 100 being the bottom of the scale on the test strips. So I don't see how using test strips would have prevented a reasonable diagnosis of this pool. In either case, the CYA was very high, which appears to be the problem.

I don't believe that maintaining a pool has to be a overly precise or difficult ordeal. My goal is to find a safe range to work within. If I get my CYA somewhere between 40 and 60 ppm and maintain FC levels between 3 and 10 ppm, pools should stay clear. So why do I need to know my FC down to within 1 ppm? Why do I need to know if I'm at 40 as opposed to 60 for CYA. The way I see it, I should be OK with either/or and anywhere in between. If I'm faced with 100 ppm CYA, its not really critical if its really 90 or 110ppm, its too high in either case. Am I wrong about this? As I said, I'm not writing off a good test kit just yet, but I do feel like I can do quite well without it.

 

[FamilyGuy]

Let me ask you this. When driving at night in the rain would you want fully working wipers and headlights or one low beam and a intermitent setting only on your wipers?.........edit: Just saying

 

[chem geek]

Thanks for the info. I listed your posts to emphasize that most issues were not related to a possibly high CYA level and for those that might have been, we don't really know since in some cases it wasn't disclosed and in others they were test strip readings.

You are lucky and fortunate that your test strips, especially for CYA, are giving you decent ballpark results. We've seen lots of cases where that was not true and you may find that the strips are consistent with the turbidimetric test in some pools and not in others. However, you are going to get a lot of posts from people who are frustrated trying to help you if you just report test strip numbers because their range is too broad (i.e. not enough resolution -- see this post) and they are often not accurate.

It is a chemical fact that if you only use Trichlor in a pool, then the CYA will rise unless there is significant water dilution -- there is no getting around that. One can get lucky over the winter with the CYA dropping significantly (probably due to bacterial conversion fortunately to nitrogen gas though sometimes to ammonia). A pool high in CYA (and not high enough in FC) is not guaranteed to get algae because algae also requires nutrients and will also be inhibited by algaecides. That's why most pool services that primarily use Trichlor tabs either use higher FC levels, shock the pool with unstabilized chlorine weekly (or when there is a hint of a problem) or use algaecides (linear quats, Polyquat, copper, borates) or phosphate removers or some combination of these techniques. Some of these approaches are better than others, but none is ideal and just masks the core issue of rising CYA levels from stabilized chlorine products.

There is no question that it is tough managing a pool only weekly which is what makes Trichlor pucks so seductive because they are pretty much the only slow-dissolving form of chlorine (there are also Cal-Hypo pucks for special feeders but they tend to break down into a mess with lots of binder material). The other primary approach is a large FC swing with a high CYA level using unstabilized chlorine which is what some services do with chlorinating liquid, chlorine gas, or some combination. Of course, once one adds automation to the mix, then things become much easier for weekly maintenance as with saltwater chlorine generators, peristaltic pumps, and The Liquidator.

 

[TreeFiter]

Thank you chem geek. I get where you, and most of the others commenting on my posts are coming from. But I don't think it is less than reasonable to come to this forum with the expectation that knowledgeable people with an understanding of what is going on in these pools might be able to think outside the box a little bit. I come here looking for help, but instead hear the same useless criticisms over and over again. Most of the times the criticisms are missing the mark. Before I can get one helpful suggestion, like try cal-hypo or liquid chlorine, I get 3 or 4 simply criticizing the use of trichlor. This isn't constructive. And considering trichlor tablets are pretty much the industry standard for chlorine delivery, I would say its reasonable to think that people can use them without too many problems.

I applaud the people that have come to me with useful information, and helped me better understand what is going on and causing the problems I see. Jason Lion and chem geek are two that have offered vast amounts of insight. Because of this kind of help, I have found ways to better serve my customers on a daily basis.

To the others that feel the need to stand on their soapboxes and preach at me about how wrong it is to use a certain chemical in a pool; there is more than one way to skin a cat. 90% or more of the pools I maintain are flawless. It is only a handful that give me problems. There are often many factors beyond my control, which makes it even harder to maintain some of these pools. So please try to put this all into perspective as you try to talk down to me after maintaining a single pool in your own back yard where you have access to it 24/7 and full authority over everything that is done to it.

 

[chem geek]

And considering trichlor tablets are pretty much the industry standard for chlorine delivery, I would say its reasonable to think that people can use them without too many problems.

Well, that simply isn't true and the fact that this forum is already viewed by over 4% of all pool owners in the U.S. (over 400,000 people visiting this site in the month of June; over 53,000 registered to-date) and growing at a rate of 30% per year and that many, many posts of users with algae in their pools is from improper FC/CYA ratios and that the science shows it to be true is why Trichlor-only use is discouraged. People can use Trichlor in their pools if they know the consequences and deal with them. Pool services only visiting weekly do not have as many options. I've spoken to several pool services who service a thousand or more pools and they all see the FC/CYA ratio in effect even though they do not understand it and they all deal with it in different ways -- some with higher FC, some with extra unstabilized chlorine dosing (shocking), some with water dilution to lower or cap CYA levels, some with algaecides, some with phosphate removers.

And yet most of the thousands upon thousands of pool owners on this forum manage their pools with the proper FC/CYA ratio and no use of phosphate removers, algaecides, weekly shocking, clarifiers, flocculants, enzymes or other products. So it works, but does require more frequent manual dosing or automation.

So I agree with you that people shouldn't be trying to force you to do things out of your control and instead should just give you the facts so that you can choose to do what you can, but your situation is quite different than pool owners who can dose more frequently. In my own pool, I have a mostly opaque electric safety cover so have relatively low 1 ppm FC per day chlorine in usage even though the pool is used every day for 1-2 hours and is at 88ºF so that lets me dose with 12.5% chlorinating liquid about twice a week instead of every day or two.