New Pool Owner Pool Has Been GREEN for a Month

[chem geek]

pool tech,

I'm not saying that using a phosphate remover won't prevent algae. I'm saying that phosphate removers are expensive and unnecessary since chlorine alone will prevent algae if maintained at the appropriate level relative to the CYA level. A maintenance dose of PolyQuat 60 algaecide will also prevent algae and not have one worry about CYA level. So there are different options and methods. It's not "I'm right and you're wrong" -- nor is it "everyone is entitled to their own opinion" with regard to using phosphates.

Since some of your high CYA pools with the chlorine levels you are maintaining (that I suspect is less than 6 ppm FC) get algae, then that is consistent with what I have been saying and the chemistry behind chlorine and CYA. Phosphates are algae food -- they do not "create" algae so clearly the amount of chlorine in the pool was insufficient to kill the algae and even at "ideal" algae food levels of phosphates, nitrates and carbonates, there is a limit to their growth rate (roughly 3 hours per generation) so if chlorine can kill the algae faster than it reproduces, the algae will not grow. You said that was not true, but that is wrong -- chlorine will kill algae even under ideal algae growth conditions and in fact has been done over and over again in many labs as well as hundreds of residential pools as reported on multiple pool forums. Your recommendation of shocking to 10 ppm FC will not kill an algae bloom if there's plenty of algae food -- you are right about that -- but it's because to quickly kill algae in a bloom you need 40% of the CYA level which at 80 ppm CYA would be 32 ppm FC and to kill an algae bloom slowly you would need 20% of the CYA level which would be 16 ppm FC. So it's no surprise that 10 ppm FC doesn't work for some 80 ppm CYA pools -- it's way too slow and the large amounts of algae use up the chlorine much too quickly.

In your pools in sunny and hot Sacramento, you want to run them with higher CYA levels because you don't want to lose the chlorine to sunlight as quickly. 60-80 ppm CYA is also the recommended range for most saltwater chlorine generator (SWG) pools for the same reason -- so they can run at a lower rate since there will be less chlorine loss during the day due to sunlight (UV rays). So the plus side at the higher CYA levels is that with lower chlorine loss you use less tabs and have less risk of running out of chlorine. But the downside is that unless the Free Chlorine level is kept high OR phosphates are kept low OR a weekly algaecide is used, then the risk of getting algae is higher. And constantly using Trichlor tabs will have the CYA keep rising unless you do significant backwashing or other dilution. I'm not saying that someone HAS to lower the CYA -- I always say that they can maintain a higher FC level instead as another option. However, killing an existing algae bloom at high CYA levels IS hard as it takes a LOT of chlorine -- so at that point the expensive phosphate remover starts to look like a better option (algaecide with copper will also work, but then you've got copper in the pool to deal with).

By the way, phosphates typically come from fertilized soil or blown-in fertilizer since that contains phosphates and nitrates -- that is, plant food. Have you ever had a pool you treated with phosphate remover develop algae again at some later point in time? If so, then this means that such a pool is getting regular additions of phosphates so will require periodic phosphate remover. Though that can certainly be done, one could instead just maintain a higher chlorine level appropriate for the CYA level (or can use a weekly PolyQuat 60 algaecide is mentioned earlier).

At very high CYA levels, above 150 ppm, there are potential problems with corroding plaster as seen in this link.

So with your 80 ppm CYA pools, what is the minimum Free Chlorine (FC) level that you maintain? I'm curious as it will give me an idea of typical low FC levels that can be maintained in many pools, but not those with higher phosphates that you then treat on a case-by-case basis. To not need the phosphate removers at all, the FC level would need to be a minimum of around 6.0 ppm (7.5% of the CYA level) to not get algae in even high phosphate pools and my normal recommendation for a "target" FC level is 11.5% of the CYA level (so 9.2 ppm with 80 ppm CYA) since that gives some buffer for error as people often have a hard time consistently making sure they never drop below the "minimum". These levels weren't made up by me -- they came from Ben Powell at The Pool Forum in his original chlorine/CYA table (see this link) and he, too, serviced large commercial pools. I refined the data based on the actual chemistry involved. So his experience and yours are not different -- you just chose a different solution than he did, but that doesn't make one right and the other wrong.

Richard

[pool tech]

I keep my cl2 levels between 3-5 ppm TA 100-120 PH 7.4 CYA 80-100
CH 240-400 on all my pools. If I am maintaining these pools all year round 1 or 2 will start to turn green on me during the summer. That is a very low percentage considering I maintain 100 pools. When the pool starts to turn I check all my chems to make sure their in range and I then check for phosphates. If the phosphate levels are low I just shock the pool with 2-4 gallons of chlorine and it takes care of the problem. If the phosphates are high the chlorine shock will not work unless I remove the phosphates from the pool. Either way the pool ends up crystal clear for the rest of the year and it generally takes only 2 days to clear up. This method works for me without failure here in sacramento. You may have it different where your at.

[chem geek]

pool tech,

The 3-5 ppm FC with 80-100 ppm CYA is right on the edge of where algae will develop IF it has enough food to reproduce faster than the chlorine can kill it (the 3 ppm FC with 100 ppm CYA is the most susceptible). So you are fortunate that most of your pools don't have lots of phosphates or otherwise encourage fast algae growth. Keep in mind that at lower amounts of algae, the pool won't be green, but will look cloudy or just "dull" where the main drain isn't crystal clear as if looking through a glass of water, but you reported the water looking crystal clear so that's good. Also, if there is this nascent algae with dull water in the pool, then chlorine consumption is higher so shocking and then maintaining higher FC levels can actually reduce chlorine consumption. This most often shows up in SWG pools where they are running just a little too low in FC and then can't set the SWG high enough to keep the pool clear.

So thanks for the info as it means that the recommendations are conservative, at least for green algae. Quite a few residential pool users with 3 ppm FC and 100 ppm CYA report getting green algae. Now, there have been reports of yellow/mustard algae, usually around this time of year (August) and we've found (through experiments with a few pool users on pool forums) that this algae requires higher levels of chlorine to keep away -- around 15% of the CYA level or about twice the minimum amount needed for green algae. So that is another situation where the phosphate removal application is an option if one doesn't want to maintain higher FC levels as it should take care of mustard/yellow algae as well. I'm less clear as to whether PolyQuat 60 is as effective at preventing mustard/yellow algae -- Buckman Labs says its effective, but I haven't seen real pools with that combo so don't know for sure.

I'm not a pool service person -- I'm an individual pool owner. I just collect the info from a variety of pool forums and work out the chemistry of pool water. Along with some other pool forum users, we've worked out some things that are counter to what the pool industry normally believes. Such as how to lower TA (through aeration at low pH rather than the "slug" method of acid addition) and the real source of rising pH in SWG pools (it's the hydrogen gas bubbles from the SWG that pulls carbon dioxide out of the water) and how to lower the tendency of the pH to rise (reduce aeration, if possible, and lower the TA -- counter-intuitive), bleach and chlorinating liquid are actually pH neutral when accounting for chlorine usage (which is acidic), etc.

By the way, what do you do to prevent CYA from continuing to increase throughout the season? Do you backwash more or do explicit dilution? For every 1 ppm FC you add from Trichlor pucks/tabs, this also adds 0.6 ppm to CYA so over a season it's easy to add at least 100 ppm or more to CYA (just 1 ppm FC per day over 6 months would add 108 ppm to CYA).

Richard

[Backglass]

pool tech,

Doctors and Surgeons continue to learn new techniques and never stop training. They used to fillet you open to remove an appendix...now they do it laproscopically. Does the older way work just fine? Sure! Is it the most efficient, cheapest and fastest? Probably not.

You maintain over 100 pools. I maintain one. You have one or two turn green in a season. Mine has yet to turn green. If you want to spout numbers as proof of knowledge, my ratio's better.

I have no doubt you know a lot about pool mechanics, but you should take some time to fully investigate the latest techniques of water chemistry. It will make you a better pool surgeon!

"Open your mind Luke!" - Obi Wan Kenobi

[chem geek]

I appreciate and want pool tech's feedback and experiences. As I said, the recommended ranges for chlorine levels came initially from a person who serviced many large commercial pools so experience (which is analogous to experiments) is where the core information comes from and is extremely useful. My contribution is mostly matching that (and reports from hundreds of pool users on multiple forums) up against chemical theory to come up with recommendations that are consistent with both, when possible. The 3-5 ppm in pool tech's pools is probably maintained better than what most residential pool users do and perhaps is part of the reason for the less frequent green algae in his pools.

Even the Pinellas County pool study in Florida (see this link for links to it and my analysis) had only 4 pools with green algae out of 486 pools and none of the 49 pools with ZERO chlorine had any green algae even though (as expected) most ( 28 ) were bacteriologically unsafe. This, however, is not the experience of most residential pool users. Most pools will develop green algae if left untreated without chlorine. So this is why I thought something else was going on such as use of an algaecide (or phosphate remover) in the Pinellas pools. Also note that in the Pinellas study there were 5 pools with over 5 ppm FC and a total of 9 pools with over 4 ppm FC that were bacteriologically unsafe and some of these pools had zero CYA. So clearly there are other substances making chlorine ineffective, but nobody looked into that.

So I really appreciate and value pool tech's experience and would still like to know what he's doing to keep the CYA level from rising since that is the primary problem when using Trichlor as the sole source of chlorine in pools.

Richard

[pool tech]

Honestly I don't worry about the cya level in residential pools only commercial where regulations want it below 100ppm. I have found no corralation between cya levels and chlorine consumption. I can have a pool with 80ppm cya and one with 180ppm cya and can keep both between 3-5 ppm chlorine with the use of 2-3 tabs per week without any cloudiness or algea growth.

[chem geek]

pool tech,

I'm getting confused by some of the information you've given so please help me sort this out. From your posts, the procedure you use is to check the water chemistry and if the CYA isn't 80 ppm, you raise it (so the pools you service all have at least 80 ppm CYA) and when algae appears to be starting (probably dull or cloudy water, before it turns full green) you raise the FC to 10 ppm as that works for algae problems in most of the pools you service. If the phosphate level is high, then you use a phosphate remover which will work in those pools. If none of that is the case and doesn't work (along with checking the filter and circulation, etc.), then the water is old, has too high a TDS, and a drain and refill should be done.

You said you service 100 pools per week, including commercial pools, so a mix of residential and commercial pools. You say you've serviced 30,000+ pools which confuses me. Aren't the same 100 pools serviced each week as more Trichlor needs to be added, filters cleaned, pool surfaces brushed, etc.? Where does the 30,000+ come from? You said you maintain 100 pools so is the larger number your cumulative experience over the years (i.e. 100 pools per year times 30 years)?

You said you keep the FC at 3-5 ppm and the CYA at 80-100 ppm, but later said that this is only for commercial pools that can't have more than 100 ppm CYA so residential pools can have more. So how do you keep the CYA below 100 in the commercial pools? I assume those tend to be larger pools, at least 15,000 gallons and probably 30,000 gallons or more -- is that correct?. In such large pools, there isn't a lot of dilution, even with sand filter backwashing, so how do you keep the CYA below 100 if you are using Trichlor all the time? Do you switch to an unstabilized source of chlorine or do you do a partial drain/refill every few weeks to keep the CYA below 100?

For the commercial pools, since they are all at 80-100 ppm CYA, there isn't going to be any correlation available between CYA level and algae development. So it's the residential pools that are of more interest. So what you are saying is that when the water starts to turn (look dull or cloudy), you test the water chemistry including CYA, right? And have you found that as many pools with very high CYA well over 100 ppm get algae as frequently as pools at 80 ppm -- both with comparable FC levels? Now I would expect that the pools with lower CYA levels would be those that have more dilution -- so smaller pools with sand filters backwashed weekly, for example. Larger pools with cartridge filters would more likely have higher CYA levels. So looking at it that way, do you see any correlation between which of those sets of pools get algae more frequently?

And I want to just make sure -- you aren't using any algaecide in any of these pools, correct? No copper, PolyQuat, linear quat, or borates (Proteam Supreme, etc.), correct?

2-3 Trichlor tabs (if the 3" 8-ounce weight variety) per week in 15,000 gallons would be 7.3 to 11.0 ppm FC and 4.4 to 6.7 ppm CYA per week. That's 1.0 to 1.6 ppm FC per day which is somewhat low for full day exposure to sunlight and some bather load. When you said 2-3 tabs per week are these for smaller pools or pools in partial shade or using an opaque-to-UV cover? Also, after 6 months the CYA would rise by 114 to 174 ppm less whatever is diluted. If you aren't measuring such high levels, then is this due to lots of backwashing, splash-out, intentional dilution (partial drain/refill) or much larger pools than I assumed?

Since you mentioned the part about old water and TDS, the pool industry used to think that high TDS was a problem, but in fact the high TDS was just a proxy for having a high CYA level (and usually meant higher CH and salt levels as well). Older water usually had higher CYA levels if stabilized chlorine was always used and the pools didn't have lots of dilution (lots of dilution would be found in smaller pools with frequent backwashing or splash-out, for example). You said, "I can have a pool with 80ppm cya and one with 180ppm cya and can keep both between 3-5 ppm chlorine with the use of 2-3 tabs per week without any cloudiness or algea growth.", but the question isn't having pools with different CYA levels that don't get algae, because there are several factors needed to have algae. The question is whether the pools you have that DO start to turn (and you have several of those each year) have lower or higher CYA levels -- both those pools that get "fixed" by 10 ppm shocking as well as those pools with high phosphate levels where you then use a phosphate remover. So have you found that the residential pools that started to turn (regardless of phosphate level) were both low and high CYA levels in similar numbers (in proportion to the CYA levels in the residential pools)? Or did it appear that pools that couldn't get fixed with 10 ppm FC had phosphates and high CYA both?

I'm just trying to reconcile what has been reported by residential users on multiple pool forums (and Ben's experience with commercial pools) where most pool users reporting algae either had minimal or no chlorine (i.e. < 1 ppm FC) or had high CYA with too low a relative FC (all were below 7.5% of CYA level) including pools with very high CYA (> 150 ppm) where even seemingly OK FC levels of 3-5 ppm did not keep away algae -- and shocking with 10-15 ppm FC was not enough. Because phosphates are a nutrient for algae, it's easy to just write this off as high phosphates, but even pools with high phosphates (3000+ ppb) have had algae controlled with chlorine levels scaled to the CYA level for almost all users (only 3 out of several hundred pools that developed algae had recommended FC/CYA ratio levels and we're not positive about all three -- one had 10,000 ppb phosphates so could require more than the recommended FC/CYA ratio) so there has to be more to the story than just phosphates. I suspect that many of your algae-free 5 ppm FC, 80 ppm CYA pools actually have similar high phosphate levels to those that got algae at 3 ppm 150 ppm CYA.

Richard

[mr_clean]

I have been reading all this and notice a few things:

everybody but pool tech must be from the mid-west or east but not the west coast.

everyone seems to be using sand filters

almost everyone seems to have 20,000 gal or below pool sizes

Phosphates do not seem to be an issue but on west coast, I am wondering
do most backyards not have alot of plant/tree life?

Does anyone actually have a test kit for phosphates?

How many hours a day does everyone run their filter winter/summer?

all pool stores except on west coast are just tryin to rip you off or know nothing at all.


BBB is going to start being sold by AARP to help anyone 65 or older pinch another penny (sorry I thought it was funny not tryin to spread hate)

[Guest]

If you look at the locations of pool users and service techs in postings on this and other forums, you'll find that they are all over the country, including the west. I live near San Francisco, for example. In my county north of S.F., we have to use cartridge filters since we are under water restrictions and water is very expensive as well.

There are some residential pool users with 8-10 foot deep pools that are larger (20' wide or larger) and are from 30,000 to 45,000 gallons, but you are right that most have inground pools around the 15,000-25,000 gallon range and above-ground pools, including Intex are smaller at around 7500-15,000 gallons (though there are exceptions). It's not surprising that there are more smaller above-ground pools as these are less expensive.

Phosphate removers are promoted in pool stores around the country, but I suspect that phosphates are found in most pools. It's just that those with sufficient chlorine levels don't get tested for them so you only see the "problem" pools and by definition they have to have at least some phosphates or else the algae won't grow.

AquaChek makes a test strip called the AquaTrend Phosphate test and Taylor makes a K-1106 kit for testing phosphates. Both test up to 1000 ppb but through dilution could test higher.

Phosphates do not seem to be an issue but on west coast, I am wondering

I don't think pool run times are relevant since pump sizes and flow rates vary. What's more relevant is the number of turnovers per day. Most pool users report one turnover per day but how much is really needed is a function of how much debris and organics get into the pool as well as pool circulation (above ground pools without a floor drain tend to have poor bottom circulation though pointing the return diagonally down and to the side helps create a circular motion).

Richard

[chem geek]

Sorry -- I forgot to log in on that last post. You are right that a count of filter types on the forums (which is not necessarily a good statistical sample) does appear that sand is the most common, then DE and cartridge, but it seems to vary based on region. For cleaning efficiency, DE is best, then cartridge, then sand (generally), but people can add some DE to their sand filters (add some to the skimmer to get the PSI up a couple) and get the best of both worlds -- the convenience of backwashing sand filters with the filtering efficiency of DE (you need to add more DE to the sand filter after backwashing, but since it's such a small amount it's pretty cost efficient).

Richard

[mr_clean]

I don't think pool run times are relevant since pump sizes and flow rates vary. What's more relevant is the number of turnovers per day. Most pool users report one turnover per day but how much is really needed is a function of how much debris and organics get into the pool as well as pool circulation (above ground pools without a floor drain tend to have poor bottom circulation though pointing the return diagonally down and to the side helps create a circular motion). [quote]

Run times to me come into effect with algae problems when:

how old equipment is, you would be suprised

what size equipment

is filter dirty

the debri amount in pool

how pools are shaped and return lines

how many return lines there are

how much it is being used

what time of year-heat

If it's above ground some have one returnline in the middle of wall with no control also tiny cartridge filters

I am not trying to say just green but to me more common yellow which will turn to green.

No matter how well we dial in chemicals if it does not filter long enough chemicals get used up.

As equipment gets older run times can lessen

I was also thinking how many of these people with problems brush enough and correctly as I have seen algae grow in pools with chemicals perfect. I am sayin corners of steps ledges etc. it spread's

[chem geek]

Yes, you're absolutely on the money with regard to circulation. I just meant that running 16 hours a day at 25 GPM is not much different than running 8 hours a day at 50 GPM if circulation is normally OK. Both have the same turnover rate, but it's true that in pools that don't have good circulation, that more time can somewhat make up for that by giving the poor circulation areas a little more mixing and less "stagnant" time.

I have found that using GLB Party Blue dye is a good way to see the circulation in a pool (plus the pool is a fun blue for a couple of days). Another is to get a water sample for measuring chlorine by turning the tube upside down and slowly sample water in an area of interest turning the tube upright when at the right depth (and doing all of this when the pump is off helps, too). One can also use a turkey baster to carefully collect a sample (this is also useful for collecting suspect algae to view under a microscope or to settle in a jar for "feeling" it).

And you're also right on the money with regards to brushing. That helps a lot to prevent biofilm formation and to expose any surface algae to chlorine. This is most especially important in preventing black algae which grows very slowly but takes advantage of a lack of brushing by forming a slime layer. I brush my pool once a week -- it forces me to get some exercise (remember, I'm pretty much a nerd)!

Richard

[canadug]

I had an issue with algae in my pool for close to a week. I shocked the heck out of the pool but the green didn't go away. Two days later I shocked it again. Nothing changed. Backwashes did nothing for it. I did some research on the internet and figured out that the algae was dead but too fine grain to be caught in my sand filter.

I used 200 MLs of a liquid clarifier that made the smaller particles of algae join together. The 1 L bottle only cost about $12 (CDN) and did the trick. I then vacuumed the pool each day and then did a backwash.

Hope this helps!

I found this url really helpful:

www(dot)wikihow(dot)com/Determine-Which-Pool-Algaecide-and-Pool-Clarifier-Is-Best-for-Your-Swimming-Pool

Here's a blurb on flocing agents.

www(dot)poolstore(dot)co(dot)uk/shopscr16.html

[chem geek]

Thanks for the tips. When a pool doesn't clear on its own, especially in an above-ground pool without a floor drain, then using OMNI Liquid Floc Plus will consolidate particles and have them fall to the floor where they can be vacuumed to waste. A clarifier which consolidates particles to be filtered out only works well when the circulation is good. And you are also right that if the filter isn't doing a great job, that a clarifier can help, but for a sand filter you can also add a little DE to it and get the best of both worlds (see this post).

In a situation where shock does not turn the pool from green to a blue-green cloudy color, then there is more than algae in the pool. Algae will not remain green after exposure to proper shock levels of chlorine. The green chlorophyll will literally get bleached out. See this link for what a pool with algae that gets shocked looks like. If the pool is a stronger green after shocking, then it is more likely that there is copper in the pool and that the shocking with a hypochlorite source of chlorine has raised the pH and precipitated copper carbonate (which is blue-green -- see this link).

At any rate, a clarifier or floc will speed up the process, but if it's truly just alage and not copper in the pool, then chlorine alone will clear the pool over time, as shown in the link, but it does require more patience and good pool circulation.

Richard