Reaction between Aluminum and my Chlorinated pool water?

[Bm2986]

Moderator comment: This post was separated out from this thread: Reaction between Aluminum and my Chlorinated pool water?

Hi,
I'm experiencing a similar problem with water quality in a tank. Current specs of my set up are: 270,000 gallons, (960,000 litres), of chlorinated pool water. It's a large tank with a set built inside (for the film industry). There is a large set submerged inside the tank. It's mainly built out of aluminum, and plastic, and a bit of Fibreglass.

The walls of the set are painted and covered with a sealant. However, the aluminum coated with a sealant but, It's all boxed aluminum. The ends are open allowing for water to enter the inside of the tubing.

We are running 7 brand new Pentair cartridge filters, and 4 brand new Hayward sand filters. The water is heated to 89 degrees Fahrenheit.

We filled the pool with fire hydrant water, and it was clear when the pool was filled. Three days later the water turned quite murky. The pool is 12'8" deep, and it's a struggle to see submerged items on the bottom in normal light.

We have shocked the pool, and have tried many chemicals to clear the water. We've had the water tested at a local pool place that is a standard pool water test. The water came back normal.

The water still remains murky. Any ideas with the above mentioned?

 

[tim5055]

Cloudy water generally means something is growing in it.

You don't say how/how much chlorine is being used.

Saying "The water came back normal" means nothing, we need a full set of accurate test results. Not much credence is given to pool store testing around here. While you would think that a "professional" would be the best, unfortunately in most cases it is quite the opposite. Between employees who blindly trust the word of chemical sales representatives and high school kids working in the pool store for the summer you end up with poor results from their testing. But, what can you do?? We base our pool care system on accurate testing and only adding what the pool needs, when it needs it. To do that you need your own accurate test kit.

In Canada you are limited to the Taylor K-2006 test kit or the LaMotte 7022 test kit.

 

[Bm2986]

Cloudy water generally means something is growing in it.

You don't say how/how much chlorine is being used.

Saying "The water came back normal" means nothing, we need a full set of accurate test results. Not much credence is given to pool store testing around here. While you would think that a "professional" would be the best, unfortunately in most cases it is quite the opposite. Between employees who blindly trust the word of chemical sales representatives and high school kids working in the pool store for the summer you end up with poor results from their testing. But, what can you do?? We base our pool care system on accurate testing and only adding what the pool needs, when it needs it. To do that you need your own accurate test kit.

In Canada you are limited to the Taylor K-2006 test kit or the LaMotte 7022 test kit.

Approximately 24 gallons of chlorine had been add over 20 hours. That brought the reading up to 8-9ppm. In the last 8 hours we've brought the level back down to 1-2ppm of chlorine due to people going into the pool.

We have our own pool test kits on set, and have used these kits many times before. We took the water to the pool place so we could get a printed out copy of the readings typically found in a pool. This was an attempt to disprove that it was not the water and chemicals, but the foreign material in the pool making it murky.

By saying the water test returned normal, I was referring to it being with the normal operating parameters of the test. Showing that ideal range of chemicals in the pool. I understand the likelyhood of the test being inaccurate, but it was mainly just to have a paper copy.

The water has been in the pool for seven days now, 4 of them where's it been at 89 degrees farenheit. Pumps, filters, and heater running 24/7.

 

[Bama Rambler]

It's going to be hard to help from the generalities that you're giving us.

Murkiness can be caused by many things including the 'set' materials. A reaction to the aluminum is probably not causing the cloudiness, but any mill scale, oil, etc. that was left inside the extrusions could be dissolving in the water causing it. The rest of the materials and even the sealant could be causing the cloudiness. Paint will definitely cause cloudiness in the water.

 

[chem geek]

You can look at 100 Reasons for Cloudy Swimming Pool Water if you want ideas. If you want us to help you, then you need to post a complete set of water chemistry parameters measured in an accurate test kit.

Specifically, Free Chlorine (FC), Combined Chlorine (CC), pH, Total Alkalinity (TA), Calcium Hardness (CH) and Cyanuric Acid (CYA).
Also the salt level or at least if it's a saltwater chlorine generator pool.
The pool surface (is it all aluminum?).
Whether a cover is used (probably not in your case).
Whether the pool is exposed to sunlight.
The source of your chlorine (chlorinating liquid or bleach, Cal-Hypo, Trichlor pucks/tabs, Dichlor, etc.).
What you use for pH adjustment (Muriatic Acid, sodium carbonate).
The bather load in the pool -- how many bathers in the water for each hour or a net of bather-hours if you can estimate that.

 

[tim5055]

We have our own pool test kits on set, and have used these kits many times before. We took the water to the pool place so we could get a printed out copy of the readings typically found in a pool. This was an attempt to disprove that it was not the water and chemicals, but the foreign material in the pool making it murky.

By saying the water test returned normal, I was referring to it being with the normal operating parameters of the test. Showing that ideal range of chemicals in the pool. I understand the likelyhood of the test being inaccurate, but it was mainly just to have a paper copy.

What is the CYA/Stabilizer level and how much sun is the pool subjected to. A common misconception in the pool industry is that there is a "normal" level of chlorine in a pool, generally referred to as 1-2 or 2-3 ppm. The chlorine in the pool should be set in relation to the amount of stabilizer as you will find in these charts. Too much stabilizer and the chlorine is not effective and stuff will grow. Too little stabilizer and all your chlorine will be lost to the sun in a matter of a few hours. With no stabilizer your 20 gallons could be consumed by the UV of the sun quickly.

I'm totally confused by this statement "I understand the likelyhood of the test being inaccurate, but it was mainly just to have a paper copy." Why have a paper copy of inaccurate testing?

You also are repeating a common misconception, that the chlorine should be brought down to 1-2ppm for folks to go into the pool. It is safe to swim up to shock level, which again is on these same charts.

As dave said, "It's going to be hard to help from the generalities that you're giving us. "

 

[Bm2986]

Standby. Just gathering up the data. I appreciate everyone's help with this.

 

[DirtyPool]

Hi all,

i'm working with Bm2986 on the pool in question..

Here are some numbers:

free chlorine: 1.38 ppm
total chlorine: 1.61 ppm
combined chlorine: 0.23 ppm
pH: 7.5
Hardness: 135 ppm
Alkalinity: 82 ppm
Cyanuric acid: 2 ppm
Copper: 0 ppm
Iron: 0.1 ppm

the pool is inside with no sun exposure.
pH adjustment is with Muriatic acid.
the pool liner is fish grade pond liner.
there are between 10 to 20 people in the pool, half with scuba gear.

the set construction is aluminum framing with painted PVC walls coated / sealed with a Polyurea coating. This coating was tested for weeks in water with no issues.

everything in the pool was washed and / or treated, but there may be some residual grease or oil from galvanized pieces. These would be in very small quantities.

thx

 

[tim5055]

I still think at some point the chlorine levels have dropped and something is in the water other than a contaminate. The numbers you are providing are indicative of those provided by a pool store using a LaMotte WaterLink® Spin Lab, where they squirt a little water in a disk and place it on a spinner and the computer spits out very percise levels. The problem is that when well clean and calibrated I have seen good numbers form them but when otherwise the numbers are way off.

Do you have your own quality test kit? In Canada that would be a Taylor K-2006 or a Lamotte 7022. I would love to see less precise accurate numbers and have you conduct an Overnight FC Loss Test (OCLT). to prove/disprove growing things in the water.

The other issue involved is that with "workers" in the water I would assume you have created a commercial pool and do not have any idea on the Canadian regulations regarding commercial pools.

 

[chem geek]

We've seen other pools with scuba divers and the issue is mostly from the greases and chlorine reacting with the scuba gear as well as from all of the material brought in on the suits if those suits are used elsewhere on real dives (i.e. in the ocean). The solution in some of those pools was extreme filtration with very fast turnovers and the use of slime bags or other very fine filtration systems.

Also, by not using any Cyanuric Acid in the pool the active chlorine level is too strong and will oxidize those scuba suits faster.

See this thread for a nearly identical problem and particularly this thread that says things like the following:

A diver with full gear consumes like double if not more FC than a regular swimmer with simple lycra swim suit or shorts.
I have taken all pre-caution that scuba tanks for pool use stays for pool use and not allowed to be used at sea. All dive gear rinsed clean before entering the pool. Without all these pre-caution the very-very small particles will cloud the pool.

He is using around 1.5 ppm FC with 25 ppm CYA. Though he uses ozone, the water clarity is maintained largely by making sure the dive gear is clean and by supplemental filtration with a slime bag.