Sodium tetraborate decahydrate for algae

Algae problems in swimming pool water.
Green (cloudy) water or slimy pool walls.
Black algae. Mustard algae. Pink or white pool mold.
South TX Poolguy
Pool Enthusiast
Pool Enthusiast
Posts: 24
Joined: Wed 11 Jul, 2007 22:30

Sodium tetraborate decahydrate for algae

Postby South TX Poolguy » Wed 11 Jul, 2007 22:52

I have a pool that has high use and trees over the pool. I have yet to have the pool hold any chlorine level from week to week. pH= 7.6 cyanuric acid=50 Alk= 100. I have removed phosphates but it will still turn green after rain.

The DE filter grids were replaced last month. Last week I backwashed the filter and added DE. The pressure was 13. This week the pool was barely circulating and the pressure was 30. Backwashed and new DE put it back to 13. I suspect their bird dog is also swimming. This pool is an awsome dirt remover. It clears up in 24 hours. They run the pool 24/7.

It uses a chlorine floater but I basically have to use shock each week to get the level up, but it drops by the next week. I put in 5 tri-clor tablets each week.

I am considering a borate treatment. The stuff costs 46 bucks per 10,000 gal. The pool is near 30,000.

I have heard I can use 20 mule team and get the same result at a cheaper cost. I dont know how much to add though.

Anyone ever use the stuff?

I think this would be a good test pool. Besides removing the trees, dog and swimmers, If I could keep this pool clear it would sure prove the stuff works.

Thanks for any help.


chem geek
Pool Industry Leader
Pool Industry Leader
Posts: 2382
Joined: Thu 21 Jun, 2007 21:27
Location: San Rafael, California

Postby chem geek » Thu 12 Jul, 2007 13:50

If your CYA is truly 50 ppm (did you test that yourself, or is that number from your pool store?), then you would have had to keep a Free Chlorine level target of around 6 ppm with an absolute minimum of 4 ppm at all times or else algae will grow. To get rid of an existing algae bloom would take 20 ppm FC to be maintained until the algea clears and you no longer lose chlorine overnight nor measure any significant Combined Chlorine.

The Borates won't have the capacity to get rid of you existing algae bloom, but would be able to prevent future algae growth. This is similar to adding a maintenance dose of PolyQuat 60 every week except the borates are there all the time and do not go away except by dilution.

First of all, you should get yourself a good test kit, a K-2006 test kit from Taylor here or from Leslie's here or the even better kit based on the Taylor kit from tftestkits here . Since you have been using Trichlor pucks, I suspect your CYA level may be much higher than 50 which would explain why you have so much algae and can't seem to hold chlorine.

See this post for general info on clearing an algae bloom.

As for how much 20 Mule Team Borax you will need, to get to 50 ppm in your 30,000 gallon pool it would take 110.4 pounds of Borax which is 23-1/4 boxes since each box is 76 ounces weight. Since Borax raises pH, it will take 842 fluid ounces of Muriatic Acid (31.45% Hydrochloric Acid) which is 6.6 gallons. You would add some Borax and then some Acid so could split your additions into portions, say one-fifth (for 10 ppm) at a time. You can measure the Borates level with AquaCheck test strips -- it's one of the few times test strips are accurate (their salt test strips are also accurate, but take time to develop). You can find much more info on using Borates at this thread on the Pool Forum (it's not accessible outside North America).

Richard
South TX Poolguy
Pool Enthusiast
Pool Enthusiast
Posts: 24
Joined: Wed 11 Jul, 2007 22:30

Postby South TX Poolguy » Thu 12 Jul, 2007 22:04

The algae is not a problem. It is already gone since yesterday and the pool is clear again. The filtering system works great.

The problem is the pool will not hold any chlorine level for a week.

I am looking for something to keep the algae from starting. If there is no CO2 shouldnt the pool not get an algae outbreak? That is my goal.

I use a taylor test kit. And I wish I had more pools with only 50 CYA. The owners do not want to drain their pools, they already have to keep up with evaporation.
chem geek
Pool Industry Leader
Pool Industry Leader
Posts: 2382
Joined: Thu 21 Jun, 2007 21:27
Location: San Rafael, California

Postby chem geek » Thu 12 Jul, 2007 22:36

Just because a pool does not have visible algae does not mean there isn't algae in the pool consuming chlorine. You clearly have something in your pool consuming chlorine. Measure the chlorine level after the sun goes down (or around then) and early the next morning. If you have more than 0.5 ppm consumption, then you have something in your pool (algae, organics, pollen) that needs to be shocked with chlorine. If not, then your chlorine loss is during the day due to sunlight and normal loss is up to half the FC on a strong sunny day (usually less, but up to half).

It sounds like your tabs are not dissolving quickly enough to have enough chlorine in your pool. If you use tabs, then for every 1 ppm FC from these Trichlor tabs you also get 0.6 ppm CYA so your CYA levels will go up rather quickly (which is why I'm surprised it's only at 50 ppm). You need to se bleach or chlorinating liquid if you want to add chlorine without CYA. You can use The Liquidator if you don't want to manually add chlorine every day or two -- if you have a pool cover opaque to UV light from the sun, then you'll only need to add chlorine 2-3 times a week.

Since your pool is under trees, it is possible you have pollen or other organics in your pool, though you should see those. Just in case, put in a skimmer sock on your skimmer basket and see if it picks up anything. Could be that you've got pollen or other stuff that is getting caught in your filter and then it is consuming the chlorine as chlorine tries to break it down. You can check your filter as well to see if it's dirty. It sounds like it picks up a LOT so maybe the skimmer sock will give you a clue as to what it is. Using a pool cover may help, but then would need to be cleaned off or removed carefully to not dump stuff back into the pool.

Richard
South TX Poolguy
Pool Enthusiast
Pool Enthusiast
Posts: 24
Joined: Wed 11 Jul, 2007 22:30

Postby South TX Poolguy » Thu 12 Jul, 2007 23:01

The pool is not mine. I cant do tests daily or I would neglect the other pools I take care of. I Just put new grids in the filter. It is an old metal can DE filter. I BW it 4 times when I change DE.

I think the dog and rain is the chlorine user. I have seen a lot of dirt in the pool, not dust, dirt like a dog who gets wet and rolls around and goes back in again.

The tabs are dissolving each week. I took over this pool in June. The floater was in the equipment area with spider webs on it. There is no auto chlorinator so I suspect the last person was using liquid. That may be why I am starting with low CYA.

I have 2 questions for you: (I read the thread about the 20 mule team experiment and I think Ill try it on this pool. The owner seems like he will be willing to pay for the chemical cost.)

1. per 10,000 how much 20 mule/muratic acid ratio will I need? I measure acid in quarts or gallons. (quarts measured by eye from the gallon jug) I know the numbers are there but I can use the 10,000 gallon ratio on other pools.

2. Can I use 20 mule instead of soda ash when I am balancing pH? I use a 2 or 3 cup scoop for soda. How much 20 mule would that convert to for each. Does the 20 mule increase TA like soda ash or like bicarb, or not at all?

Thank you
chem geek
Pool Industry Leader
Pool Industry Leader
Posts: 2382
Joined: Thu 21 Jun, 2007 21:27
Location: San Rafael, California

Postby chem geek » Fri 13 Jul, 2007 02:09

South TX Poolguy wrote:1. per 10,000 how much 20 mule/muratic acid ratio will I need? I measure acid in quarts or gallons. (quarts measured by eye from the gallon jug) I know the numbers are there but I can use the 10,000 gallon ratio on other pools.

2. Can I use 20 mule instead of soda ash when I am balancing pH? I use a 2 or 3 cup scoop for soda. How much 20 mule would that convert to for each. Does the 20 mule increase TA like soda ash or like bicarb, or not at all?

OK, now I get the situation. Thanks for clarifying that for me.

As for the Borates, it takes 589 ounces weight (36.8 pounds) which is 7-3/4 boxes (76 ounces weight each) of 20 Mule Team Borax per 10,000 gallons to raise the Borates level to 50 ppm (it's technically measured as ppm Boron). This will also require 281 fluid ounces (35 cups or 8-3/4 quarts or 2.2 gallons) of Muriatic Acid (31.45% Hydrochloric Acid) per 10,000 gallons. You can split up the dosage and add some Borax, then some acid, back and forth so as to keep the pH somewhat stable. For example, each box (76 ounces weight) of Borax needs 36.3 fluid ounces of Muriatic Acid to keep the pH the same.

Yes, you can use the 20 Mule Team Borax to raise the pH. It takes twice as much Borax by weight as it does pH Up / Soda Ash / Arm & Hammer Super Washing Soda / Sodium Carbonate to achieve the same rise in pH (technically, it's 2.09 times as much). The TA is raised by half as much with the Borax -- there are no additional carbonates added to the water with Borax. The only more pure form of base for raising pH would be Lye / Caustic Soda / Sodium Hydroxide and it takes 38.6% by weight compared to Soda Ash, but raises TA the least.

Note that the only way to raise the pH with no change in TA is to aerate the water to drive off carbon dioxide. Normally, TA moves with pH though Soda Ash is equivalent to adding Caustic Soda AND Baking Soda together.

If you use Borax for pH control, note that this will increase the Borates level so you might want to start the pool with 30 ppm instead of 50 ppm since the range 30-50 is good for algae control. Also note that Borates are unhealthy to dogs (and other animals) if they drink from the pool every day (say a quart or more) though a quart or so is the level below which no symptoms are seen in an average sized dog.

The Borates may inhibit algae, but if the pool is consuming lots of chlorine from dog saliva or hair and oils, then I don't think they will do much good as far as lowering chlorine usage, but it will let you now worry about the higher CYA levels quite so much. Keep in mind, however, that we don't know how well the Borates will inhibit algae -- say, if FC levels drop towards 0 or CYA levels get high at a low FC level. We know that PolyQuat 60 algaecide will keep away algae even if chlorine levels drop to zero for a time.

As for pH control, if you continue to use Trichlor tabs/pucks which are very acidic, then using Borates will require you to occasionally add Alkalinity Up / Arm & Hammer Baking Soda / Sodium Bicarbonate since the acidity of Trichlor will lower both the pH and TA while carbon dioxide outgassing will raise the pH with no change in TA (so the net effect is a lowering of TA over time). Usually in Trichlor pools, one just uses pH Up / Soda Ash / Arm & Hammer Super Washing Soda / Sodium Carbonate and the TA will keep going up until you get to an equilibrium point where the outgassing of carbon dioxide causes the pH to rise fast enough so that the Trichlor and Soda Ash exactly balance each other out in terms of pH and TA. Of course, this equilibrium point may be at a higher TA level that may require you to lower the Calcium Hardness to maintain water balance. Every pool is different in this regard since aeration varies. You can use an alternating mix of Soda Ash and Borax to achieve an equilibrium point at a lower TA level, but will have to experiment to see what mix is appropriate for each pool. Of course, you can just use the Borax and monitor the TA and add Baking Soda when needed -- I'm just giving you options.

Richard
South TX Poolguy
Pool Enthusiast
Pool Enthusiast
Posts: 24
Joined: Wed 11 Jul, 2007 22:30

Postby South TX Poolguy » Fri 13 Jul, 2007 20:06

It took a while but I found a store that carries Borax. I have 100lbs on order.

Do you have any more info on the danger to pets?

I have a couple of other candidate pools.

One was taken over by a new owner a couple of months ago. The sand filter was suspect to the owner so the husband and his father hack-sawed the pvc and opened it up. They stared at it for a while and walked away so the wife called me in. I put in ziobrite.
The pool was a swamp with 7 frogs and other critters. I got the water clear but the plaster looks like giant sandpaper on the walls. Algae grows in the holes every week. I shocked the hell out if it yesterday and today the chlorine level was showing >10 on aqua check strips. >5 with Taylor. The algae was gone also. I put in a ton of Algicide 50. (I got it on sale for $5.50 a quart)
If the algae stays away for a week, I think I can keep it off. I also removed the phosphates last week.
I could try the borox on this pool. They dont have dogs.

The other candidate is a guy who heats his pool in the winter and swims often. It also has trees over the pool. His pool will turn green once in a while. I killed his phosphates 3 weeks ago. He adds something that has dyed the plaster pool a light blue. The sweeper bag and wheels are blue.
His water always has looked thick. It is very clear but it looks like it is full of vodka instead of water.

Thaks for your responses, they are very helpful!
South TX Poolguy
Pool Enthusiast
Pool Enthusiast
Posts: 24
Joined: Wed 11 Jul, 2007 22:30

Postby South TX Poolguy » Fri 13 Jul, 2007 20:27

The algicide 60 is quite expensive for all my pools. I bought a bunch of 50s that were on sale. They foam very little. After testing, I used it on pools with waterfalls and they did not produce very much foam. It mostly made bubbles that lasted a few seconds. Only one person called to ask about foaming. They were in the pool 30 mins after I left and I had seen some foaming on it as soon as I used it.

I am using Regal and Pool Season brands. I think the Regal 50 has polyquat. I dont know if the Pool Season does.

Ill make sure I get polyquat 60 after my supply of 50 runs out.

I have been told not to use these type algicides with a shock treatment. They told me the shock kills the algicide. Is that true?

I am using phosphate remover PR-3000 and catalytic enzyme CV-700 from Orenda technologies.

They are also expensive but they seem to work. No algae on my pools that have been on them for more than a month.

But I cant prove they would have gotten algae if not on it.
Guest

Postby Guest » Sat 14 Jul, 2007 11:51

See this post for more info on Boron -- I give a link to a World Health Organization (WHO) document that describes toxicity studies and I summarize some calculations. I'm being conservative since it's not the amount for serious health problems, but the amount of first detectable symptoms or effects of any kind.

As for the Algaecide 50, the 50% vs. 60% is not a big deal at all, but just make sure it's actually PolyQuat and not a linear Quat. PolyQuat will say something like the following as its ingredient:

Poly{oxyethylene(dimethyliminio)Ethylene (dimethyliminio)ethylene dichloride}

For comparison, a linear quat, which can foam with aeration, has the following chemical ingredient:

Alkyl dimethylbenzylammonium chloride

I just looked up the Regal Algaecide 50 contents in this MSDS file and it is a linear Quat, not PolyQuat. Pool Season Concentrated Algae Kill II is a linear Quat that also contains copper as shown in this MSDS . Personally, I wouldn't use either, but for sure not the Pool Season product if that's the one you use since it contains copper. PolyQuat is not only non-foaming, but is more effective than the linear Quats. You do NOT use algaecides to kill an existing algae bloom, but rather only in weekly maintenance doses to prevent or inhibit algae so you don't use very much. And you might be able to use less than recommended (I talk about that below). Anyway, you can use your Regal brand until it runs out -- it's not bad, just not as effective, but the other brand, if I found the right one, shouldn't be used unless you want to add copper to the pool (in which case you have to make sure you don't have the pH rise too far, including during chlorine shocking, or else you can precipitate copper hydroxide for a blue-green pool -- and blonds can get green hair as well).

As for what happens during a shock treatment and use of these algaecides, with PolyQuat high levels of chlorine (i.e. a shock treatment) will break the polymer down into smaller pieces. These smaller pieces are still effective as an algaecide, however. Since chlorine reacts with the PolyQuat, it is true that if you add PolyQuat when shocking, that it will use up a lot of the chlorine and that is wasteful so it's true you don't want to add both at the same time and after a shock treatment (after the chlorine comes back down to normal levels) may need to add more PolyQuat to get back to maintenance levels. Technically, even lower levels of chlorine break down PolyQuat which is part of the reason you need to add a maintenance dose each month (the other reason is to make up for dilution from splash-out, backwash, rain overflow, etc.). There is a test kit, the Taylor K-9065 shown here that can test for the amount of PolyQuat in the water. One can see if they are maintaining the initial dosage level in the pool which I believe to be around 8 ppm of PolyQuat. It would be great to know if one really needs to add the recommended maintenance dose to pools, especially those with cartridge filters (i.e. no backwashing) and what happens after a chlorine shock, etc. It's not a cheap kit, however. If you decide to get it, let me know the results. This is how we figure all this stuff out when we can't get direct information from the manufacturers (and even then, I like to verify it with real field experience).

As for the phosphate remover and enzyme products, let me comment on those. First, the enzyme products. There is no question that they work to accelerate (catalyze) the oxidation of organics, but usually they are not needed. Maintaining proper levels of chlorine appropriate to the CYA level usually results in outdoor pools with no Combined Chlorine (CC) (0.2 ppm or less) nearly all the time. Sunlight helps break down combined chlorine and catalyzes the oxidation when using chlorine. Now, that said, it is true that right after having bathers with suntan lotion it will take a day for the chlorine to break it down while an enzyme will make this happen much faster. The point is that the enzyme is only necessary if people don't have patience or if they have an unusually high organics load. As for scum lines or water surface oils, these can most easily be handled with any number of sponge products that either float or are put into the skimmer -- they work great (assuming you have decent circulation in the pool).

As for phosphates, that's controversial since it's the latest rage being sold from pool stores. There is no question that removing phosphates to sufficiently low levels will prevent algae from growing since they are an essential nutrient. The problem is two fold: such removers are very expensive and phosphates will usually return since they get blown in from dirt and fertilizers. I know that Orenda believes that it is more cost effective to handle the phosphates, but I'm not so sure. With only two extremely high phosphate pools as exceptions, every pool for hundreds of users on multiple pool forums has been able to keep away green algae by maintaining the 11.5% target FC relative to CYA (minimum 7.5% of CYA) and for mustard/yellow algae the minimum target is a higher 15% of CYA level. If one wants insurance in case the FC level drops, then using a small amount of PolyQuat regularly will work very well. I suppose that's an economics choice you have to make since we don't know how long the phosphate removers, in "extra" doses, lasts to keep away future phosphate addition.

As for proving if a pool would get algae or not, if the chlorine gets to zero in a warm (88-90F) pool, odds are it will get green algae and this always starts out as looking dull, then cloudy, then green as in the reverse order of pictures in this link that shows a pool with lots of green algae upon spring opening that gets cleared using chlorine alone (though some Borax was also used, but is not needed for killing an existing bloom -- it's best for preventing algae from getting started). We know that PolyQuat will keep a pool with zero chlorine from developing algae and I suspect the same is true initially with a phosphate-free pool, but I don't know how long it takes for the phosphate treated pool to be susceptible again. I suppose one can regularly test for phosphates, but that's not a cheap test (Taylor has some, but they don't test for really low levels below 2 ppm -- 2000 ppb).

I'm just a pool owner with an interest in pool water chemistry, but since you're a person who maintains pools, you have a LOT more experience. You should read everything you can at the following pool forum and websites -- this one isn't the only one:

www(dot)poolsolutions(dot)com/sitemap(dot)html
www(dot)poolforum(dot)com/pf2/index(dot)php
www(dot)troublefreepools(dot)com/index(dot)php

It would be really helpful if you could add your experience to what we have since there are still unanswered questions and "theory" that needs to be validated (such as some items I mentioned above about PolyQuat usage).

Richard
chem geek
Pool Industry Leader
Pool Industry Leader
Posts: 2382
Joined: Thu 21 Jun, 2007 21:27
Location: San Rafael, California

Postby chem geek » Sat 14 Jul, 2007 12:44

Looks like I forgot to log on for the previous post. Sorry about that. Anyway, I forgot to mention that many of the users who maintain pools with chlorine alone do have high phosphate levels -- the two exceptions had extraordinarily high levels and even then we're not certain that a somewhat higher chlorine level wouldn't have handled the issue. As I said, treating phosphates is an economics issue -- it does work and is not snake oil. It's just that phosphates do not cause algae to grow -- they are food, that's all, and the algae can only eat so much at a time and grow so fast no matter how much food you give to them.

Orenda had said that high phosphate levels use up chlorine, but I've talked to several different chemists now and there is no known mechanism for that. Certainly, if pools develop algae even if it's not visible then chlorine consumption will go way up, but Orenda said he saw this degradation right after a return in an SWG system (I assume the consumption was well beyond that expected from dilution) so something is going on that hasn't been accounted for yet.

Richard

Return to “Pool Algae & Green Pool Water”

Who is online at the Pool Help Forum

Users browsing this forum: No registered users and 4 guests