Sulphuric acid as pool acid

Problems relating to pH and total alkalinity.
Increase ph, increase TA. Reduce pH, reduce TA.
pH chemistry advice and techniques for the pool.
Petra

Sulphuric acid as pool acid

Postby Petra » Tue 24 Jan, 2006 21:24

We have a chemical company trying to sell us sulphuric acid as "pool acid" instead of muriatic. Has anybody heard of this for public pools


Pool Balance

pH in pool water

Postby Pool Balance » Sun 29 Jan, 2006 06:33

Sulfuric acid has been used in swimming pools, though it tends to increase the level of Total Dissolved Solids quite rapidly. It also adds to unwanted sulfates in the pool water.

It is used in pools where a few cents in the maintenance budget makes a difference but is NOT recommended, especially for public pools.
Jelmo

Re: pH in pool water

Postby Jelmo » Thu 02 Mar, 2006 14:13

Pool Balance wrote:Sulfuric acid has been used in swimming pools, though it tends to increase the level of Total Dissolved Solids quite rapidly. It also adds to unwanted sulfates in the pool water.

It is used in pools where a few cents in the maintenance budget makes a difference but is NOT recommended, especially for public pools.


Do you know what side effects sulphuric acid in pool water might have, particularly on the skin?
Pool Balance

Sulfuric acid

Postby Pool Balance » Sun 05 Mar, 2006 12:31

Sulfuric acid, in low concentrations typical of swimming pool water, have no known effects on the skin, skin sensitisation or allergic reactions.

The danger from sulfuric acid is from the liquid and fumes in its concentrated form, and from the sulfates left behind in the water which increase the TDS value of the water.

The EPA guidelines for drinking water give a limit for sulfates of 250ppm, based on the aesthetic effects it has on taste and odor. It falls into the category of secondary standards, having no proven adverse health effects.
Joey

Sulphuric acid as pool acid

Postby Joey » Thu 23 Jul, 2009 12:40

Does sulphuric acid increase the sodium hypochlorite demand?
chem geek
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Sulphuric acid as pool acid

Postby chem geek » Thu 23 Jul, 2009 22:06

Not directly, but any acid that lowers the pH will have the chlorine breakdown a little faster in sunlight. [EDIT] I got this backwards -- hypochlorite ion breaks down faster in sunlight than hypochlorous acid so it's actually higher pH where chlorine will breakdown somewhat faster in sunlight. [END-EDIT] The main side effect of sulfuric acid, as well as with dry acid (sodium bisulfate) is an increase in sulfates. High sulfate levels can hurt saltwater chlorine generator (SWG) cells and splashed out magnesium sulfate can be very harsh to stone or cement (it has one of the highest salt recrystallization pressures). Unfortunately, I don't know at what level sulfates start to be a problem in these two areas (i.e. how high is "high").

A sulfate level of 220 ppm lowers the saturation index by 0.1 so high sulfate levels need higher pH, TA or CH to compensate in order to prevent dissolving of plaster/gunite/grout surfaces.
FlPoolPro

pH in pool water

Postby FlPoolPro » Thu 11 Nov, 2010 11:43

Pool Balance wrote:Sulfuric acid has been used in swimming pools, though it tends to increase the level of Total Dissolved Solids quite rapidly. It also adds to unwanted sulfates in the pool water.

It is used in pools where a few cents in the maintenance budget makes a difference but is NOT recommended, especially for public pools.



Increase in TDS is low, but as with any chemical, Muriatic, Bleach, Trichlor, Dichlors, Cyanuric Acid, etc. your increasing TDS over time.

Sulfuric is used widely in commercial pools in Florida with great success and is actually more expensive than Muriatic. At a concentration of 38% Sulfuric reduces the pH level the same as 20 degree baum Muriatic Acid without reducing the Alkalinity as much as Muriatic.

The company we purchase Sulfuric Acid from has scientific reshearch to back this up.
FlPoolPro

Sulphuric acid as pool acid

Postby FlPoolPro » Thu 11 Nov, 2010 11:46

Joey wrote:Does sulphuric acid increase the sodium hypochlorite demand?


No. Your sanitizer level will increase as your pH is lowered. Sunlite is a huge factor on sanitizer levels. for additional information pick up a K2004 Taylor water test manual at a local pool store. Aquacheck also has a great book on pool water chemistry with their test strips.
FlPoolPro

Sulphuric acid as pool acid

Postby FlPoolPro » Thu 11 Nov, 2010 11:49

chem geek wrote:Not directly, but any acid that lowers the pH will have the chlorine breakdown a little faster in sunlight. The main side effect of sulfuric acid, as well as with dry acid (sodium bisulfate) is an increase in sulfates. High sulfate levels can hurt saltwater chlorine generator (SWG) cells and splashed out magnesium sulfate can be very harsh to stone or cement (it has one of the highest salt recrystallization pressures). Unfortunately, I don't know at what level sulfates start to be a problem in these two areas (i.e. how high is "high").

A sulfate level of 220 ppm lowers the saturation index by 0.1 so high sulfate levels need higher pH, TA or CH to compensate in order to prevent dissolving of plaster/gunite/grout surfaces.


I sure would like to see some technical data on how Sulfuric hurts salt cells. The local Hayward rep has been saying that for two years but can't produce any data to back it up.
chem geek
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Posts: 2382
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pH in pool water

Postby chem geek » Thu 11 Nov, 2010 20:49

FlPoolPro wrote:At a concentration of 38% Sulfuric reduces the pH level the same as 20 degree baum Muriatic Acid without reducing the Alkalinity as much as Muriatic.

The company we purchase Sulfuric Acid from has scientific reshearch to back this up.

This is pure bunk. Please provide a link or contact phone number to the company that claims to have scientific research showing that different strong acids result in differing amounts of Total Alkalinity (TA) reduction. I will then contact them.

Adding 25-1/2 fluid ounces of full-strength Muriatic Acid (31.45% Hydrochloric Acid) or 34.4 ounces weight of Dry Acid (93.2% Sodium Bisulfate) or 26 fluid ounces of 38.5% Sulfuric Acid in 10,000 gallons all result in a lowering of Total Alkalinity of 10 ppm regardless of starting TA or pH (and also results in a pH drop from 7.5 to 7.07 if the starting TA is 100, though the drop in pH depends on starting pH and TA).

Adding a strong acid always lowers both pH and TA just as adding a strong base always raises pH and TA. If one wants to lower only the TA, then one can do so efficiently using the procedure described in this post. One essentially accelerates the process of driving carbon dioxide out of the water through a combination of aeration of the water at low pH. Pools are intentionally over-carbonated both to provide a pH buffer and to saturate the water with calcium carbonate to protect plaster surfaces. Just as stirring a carbonated beverage vigorously or blowing bubbles through a straw causes it to go flat faster, the same is true for pools via aeration. Lower pH speeds up the process as well as more of the carbonates in the water are in the form of carbon dioxide. The factor by which there is more carbon dioxide in pool/spa water than there is with equilibrium in air is shown in this chart .

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