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Hach Disinfection Series - Step 2 

2. Chlorine Chemistry

Chlorine is the predominant method of disinfecting water and wastewater and has been used for almost 100 years in the United States. Chlorine can be added to water as chlorine gas, an aqueous sodium hypochlorite solution, or solid calcium hypochlorite. When chlorine is added to water in any of these forms, it creates hypochlorous acid. Hypochlorous acid (HOCl) is a weak acid that dissociates into hypochlorite ion (OCl–) according to the following equation:

HOCl ↔ H+ + OCl—

Together, HOCl and OCl â€“ are known as free chlorine. The two species exist in an equilibrium that is pH dependent. The equilibrium is also slightly affected by temperature. As the pH increases, the ratio of hypochlorous acid to hypochlorite ion decreases. Below a pH of 7.5, hypochlorous acid is the dominant species. Above a pH of 7.5, hypochlorite ion is the dominant species. The disassociation curve below illustrates the relationship between the chemical forms of chlorine and pH at 20° C. The graph indicates a significant change in the ratio of hypochlorous acid to hypochlorite between pH 6 and 9, within the typical pH range for drinking water treatment. The steepest portion of the curve is between pH 7 and 8. Even a 0.1 unit change in pH can cause a significant change in the ratio between HOCl and OCl–. This is significant because HOCl is a stronger disinfectant than OCl–. Therefore, the chlorination process is pH dependent. The germicidal effects of HOCl will be realized by chlorination at a lower pH.

disinfectionseries01-linechrt-360x222.gi

When free chlorine is combined with ammonia, the compounds react to form chloramines, such as monochloramine, dichloramine, and nitrogen trichloride. The sum of the free chlorine and chloramines in a sample is known as total chlorine.

The various forms of chlorine-based disinfectants have varying degrees of germicidal strength and persistence in the water and are therefore used in different applications. Free chlorine is a much stronger disinfectant than chloramine, but its residual is not as persistent as a chloramine residual. Because of its germicidal properties, free chlorine is commonly used whenever possible; however free chlorine forms trihalomethanes and is often replaced with chloramines when trihalomethanes or other disinfection by-products are a problem. Since chloramines are a weaker disinfectant their concentration levels are kept at much higher than free chlorine. Since the chloramine residual lasts much longer than free chlorine residuals, chloramines are often used as a secondary residual disinfectant to ensure the presence of a disinfectant residual throughout the distribution system.

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Guest Kyle Heeter   
Guest Kyle Heeter

What is your take on this? RooSHam

It is an article stating how SH is bad for your roof, plants, overall wellbeing, and even deadly. And that the 2007 ARMA shingles manufacturers are wrong in stating that SH and TSP is the preparing way to clean. They claim their products is safe and Eco-friendly. Just looking for some incite on the subject due to the fact that my competitor bought into this business and now I am getting phone rom worried customers about the potential harm. Let me know what u think.

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What is your take on this? RooSHam

It is an article stating how SH is bad for your roof, plants, overall wellbeing, and even deadly. And that the 2007 ARMA shingles manufacturers are wrong in stating that SH and TSP is the preparing way to clean. They claim their products is safe and Eco-friendly. Just looking for some incite on the subject due to the fact that my competitor bought into this business and now I am getting phone rom worried customers about the potential harm. Let me know what u think.

Contradicting what the shingle manufacturers are stating doesn't seem right to me!

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garyw   

Powered bleach will not work. It is too weak. Google "Univar chemical". There should be one near you.  12.5% Sodium hypochlorite is what you need.

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Does anyone actually mix their own SH with beads or does almost everyone buy the jugs of liquid from a pool supply house?

Caustic Beads can be added to liquid sodium hypochlorite, to extend the shelf life of it somewhat.

When we say SH, we mean sodium hypochlorite, not sodium hydroxide.

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 Chris ,What is the deal with Soft Wash Systems and their powdered SH ?  

When it was first introduced, it left a white film all over everything, that required acid and pressure washing to remove.

We never suggest using powdered SH, because it is NOT "powdered SH".

It is NOT the same as liquid sodium hypochlorite.

It is Calcium Hypochlorite, better known as powdered swimming pool shock, same stuff as is sold at WalMart!

 

Here is an RCIA Member giving his opinion of that stuff.

 

post-1-0-34682200-1389238457_thumb.jpgpost-1-0-40855400-1389238458_thumb.jpg

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 Chris,I have been cleaning roofs about 3 years thanks to RCIA and am trying to find the right combo for my solution. I first started with SH,  alcohol , dawn soap, TSP , and water at a 40% mix. This combination worked great. As I got more involved in the RCIA threads roof cleaners were cautioning away from alcohol and TSP. I then changed my mix to SH, Dawn , ammonyx lo , and green apple masking smell. The results were not as good. This past year I started using Fresh Wash , SH at a 40 to 45% mix with better results.The thing that I noticed was that my solution did not suds up much.  As I have read since I started back to RCIA it seams that Gain has been working great as a surfactant. Except where where etching of glass must be cautioned, do you see any problems with going back to TSP ?

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No, just keep strong TSP solutions off of painted surfaces.

Gain and TSP work great together, and will allow you to drop the TSP percentage down to 1/4 cup per gallon of mix!

TSP at this low percentage will not etch glass, or harm paint either.

In fact, all it will do is clean like a mo fo.

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Chris, on a 40 gallon mix what would be your recommended TSP ratio and do you have any suggestions where I could bulk purchase TSP and Gain ?

1/4 cup of TSP per total gallons of roof cleaning mix.

Florida Chemical Supply in Tampa sells and ships TSP in Bulk, it is cheap!

Gain can be bought at any WalMart or Dollar Store

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Ok thanks Chris !!  

Anytime my friend, and remember, I am always here at 813 655 8777 from 11 am till 11 pm florida time, for one on one instructions.

No need to ever make a mistake again when cleaning roofs, or selecting equipment.

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While on he subject , If I were to check the PH of my mix could I determine if my SH was not up to 12.5 ? If thats the case would I be able to change my % of SH  to compensate  for my mix or would I be better off to add another chemical to bring up my ph ?

u r confusing PH and Chemical strength.

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Chad   

When I started in roof cleaning, a hydrogen Peroxide based cleaner was my first choice, until I started cleaning with it. It removes algae after about 5 or 6 applications.

It just did't suit my expectations as a chemical to use for my roof cleaning business. Also cost prohibitive at that application rate.

Now using SH at 3.5% with gain (per Tucker) works great!

Chad Freeman

SafePro Roof Cleaning Gainesville Fl 32607

http://www.safeproroofcleaning.net

http://www.safeproroofcleaning.com

http://www.roofcleaninggainesvilleflorida.wordpress.com

 

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Jeff   

When I started in roof cleaning, a hydrogen Peroxide based cleaner was my first choice, until I started cleaning with it. It removes algae after about 5 or 6 applications.

 

​So, are you saying after 5-6 applications of Sodium Percarbonate the roof is clean, and the need for a direct,  mild pressure rinse isn't necessary?  Or were you rinsing with a pressure washer like every other Sodium Percarbonate "user"?   Just wondering, because I'd be impressed if Sodium Percarbonate would clean a roof after 100 applications,..let alone 5-6.

*Bet you're glad you moved on to liquid hypo.

Jeff

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Chad   

Yeah it came off with low pressure but like I said it is not practical to use it as a pro roof cleaner.

SafePro Roof Cleaning

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