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Swimming pool, PH and muriatic acid ...
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Noproblem
science forum beginner


Joined: 12 Jun 2006
Posts: 1

PostPosted: Mon Jun 12, 2006 9:33 pm    Post subject: Swimming pool, PH and muriatic acid ... Reply with quote
I bought a swimming pool with 24 cubic meters of water.

For lowering the PH of the water (I have to keep it in the range 7.2 - 7.6)
a specific solid product should be used, like this:

http://www.poolsinc.com/chem_bal3.html

I read somewhere that I could use the muriatic acid, that is cheaper.

Can you tell me the exact quantity of muriatic acid should I add to my water
for decreasing the PH by 1/10?

I repeat: decreasing by 1/10 the PH for 24 cubic meters of water.

Thanks in advance.
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Borek
science forum Guru Wannabe


Joined: 02 May 2005
Posts: 157

PostPosted: Mon Jun 12, 2006 9:47 pm    Post subject: Re: Swimming pool, PH and muriatic acid ... Reply with quote
On Mon, 12 Jun 2006 23:33:23 +0200, Noproblem
<noproblem@NOSPAMMMMMMinterfree.it> wrote:

Quote:
Can you tell me the exact quantity of muriatic acid should I add to my
water for decreasing the PH by 1/10?

Impossible. Amount of acid required depends on the starting pH. Besides,it
is very likely that your water already contains some dissolved weak acids
or bases which make calculations even more complicated. It can be
calculated, but one post is not enough to explain what you should know
about pH calculation to be ready to do it.

You may check these lectures:

http://www.chembuddy.com/?left=pH-calculation&right=toc

for some more info.

Best,
Borek
--
http://www.chembuddy.com
http://www.ph-meter.info/pH-meter-construction
http://www.terapia-kregoslupa.waw.pl
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mrdarrett@gmail.com
science forum addict


Joined: 28 Dec 2005
Posts: 55

PostPosted: Mon Jun 12, 2006 9:48 pm    Post subject: Re: Swimming pool, PH and muriatic acid ... Reply with quote
Noproblem wrote:
Quote:
I bought a swimming pool with 24 cubic meters of water.

For lowering the PH of the water (I have to keep it in the range 7.2 - 7.6)
a specific solid product should be used, like this:

http://www.poolsinc.com/chem_bal3.html

I read somewhere that I could use the muriatic acid, that is cheaper.

Can you tell me the exact quantity of muriatic acid should I add to my water
for decreasing the PH by 1/10?

I repeat: decreasing by 1/10 the PH for 24 cubic meters of water.

Thanks in advance.


Carefully read the directions on the muriatic acid sold in the store
(Home Depot, etc.)

Playing with laboratory / bulk chemical muriatic acid (hydrochloric
acid) is very dangerous.
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mrdarrett@gmail.com
science forum addict


Joined: 28 Dec 2005
Posts: 55

PostPosted: Mon Jun 12, 2006 10:42 pm    Post subject: Re: Swimming pool, PH and muriatic acid ... Reply with quote
Noproblem wrote:
Quote:
I bought a swimming pool with 24 cubic meters of water.

For lowering the PH of the water (I have to keep it in the range 7.2 - 7.6)
a specific solid product should be used, like this:

http://www.poolsinc.com/chem_bal3.html

I read somewhere that I could use the muriatic acid, that is cheaper.

Can you tell me the exact quantity of muriatic acid should I add to my water
for decreasing the PH by 1/10?

I repeat: decreasing by 1/10 the PH for 24 cubic meters of water.

Thanks in advance.


Oh, from your IP address, you're in Italy... no Home Depot there, I
bet.

Normally water exposed to air is somewhat below a pH of 7, because
water tends to dissolve acidic gases normally in air (carbon dioxide,
nitrogen oxides, etc.)

So, if anything, you're probably going to want to *increase* the pH of
your water. (Unless someone has already added a whole lot of stuff to
the water to increase the pH already).

Got any litmus paper strips to test your pool's pH?
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Pepelos
science forum beginner


Joined: 11 Jun 2006
Posts: 4

PostPosted: Tue Jun 13, 2006 12:12 am    Post subject: Re: Swimming pool, PH and muriatic acid ... Reply with quote
It's no use to use muriatic acid (hydrochloric acid) because it's
dangerous.
I think you can use sodiun hypochlorite (bleach) as disinfectant.
Sodium hipochlorite is dissociating in water and results Free Chlorinne
(powerfull disinfectant agent).

Free Chlorine concentration in your pool should be between 2 - 5 ppm

For the best dissociation rate (high free chorine concentration) it
needs a pH between 7.2 and 7.6.

Here is a calculator but you will need a chemical kit to determine the
actual free chlorine level:
http://www.csgnetwork.com/poolchemcalc.html

PM: Keep in mind you are controlling the pH just to obtain the highest
dissociation rate of sodium hipochlorite, calcium hipochlorite etc. If
you dont have any chlor in there controling the pH is usless.

Good Luck
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Mxsmanic
science forum Guru Wannabe


Joined: 16 Dec 2005
Posts: 148

PostPosted: Tue Jun 13, 2006 1:39 am    Post subject: Re: Swimming pool, PH and muriatic acid ... Reply with quote
Noproblem writes:

Quote:
I read somewhere that I could use the muriatic acid, that is cheaper.

Yes, it's routine to use hydrochloric acid in various concentrations
for pool pH control. Sometimes concentrated sulfuric acid is used,
too.

Quote:
Can you tell me the exact quantity of muriatic acid should I add to my water
for decreasing the PH by 1/10?

The standard is to test the water, add chemicals to adjust pH, and
test again, until it comes out about right. A real swimming pool is
too uncontrolled an environment to try to calculate it all in advance.

--
Transpose mxsmanic and gmail to reach me by e-mail.
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Mxsmanic
science forum Guru Wannabe


Joined: 16 Dec 2005
Posts: 148

PostPosted: Tue Jun 13, 2006 1:40 am    Post subject: Re: Swimming pool, PH and muriatic acid ... Reply with quote
mrdarrett@gmail.com writes:

Quote:
Playing with laboratory / bulk chemical muriatic acid (hydrochloric
acid) is very dangerous.

Bulk hydrochloric acid is routinely used to control pH in pools. It's
not that dangerous if one exerts reasonable care.

--
Transpose mxsmanic and gmail to reach me by e-mail.
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Mxsmanic
science forum Guru Wannabe


Joined: 16 Dec 2005
Posts: 148

PostPosted: Tue Jun 13, 2006 1:43 am    Post subject: Re: Swimming pool, PH and muriatic acid ... Reply with quote
mrdarrett@gmail.com writes:

Quote:
So, if anything, you're probably going to want to *increase* the pH of
your water. (Unless someone has already added a whole lot of stuff to
the water to increase the pH already).

Chlorinated swimming pools almost always have a pH that needs to be
brought down. Usually chlorine (sodium hypochlorite solution) and
acid (hydrochloric or sulfuric) are added to the water periodically.

I'm not sure what raises the pH--the chlorine?

Quote:
Got any litmus paper strips to test your pool's pH?

There are test kits available specifically for swimming pools. Some
people just throw chemicals in once a day or so, but it's best to
test.

--
Transpose mxsmanic and gmail to reach me by e-mail.
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Mxsmanic
science forum Guru Wannabe


Joined: 16 Dec 2005
Posts: 148

PostPosted: Tue Jun 13, 2006 1:45 am    Post subject: Re: Swimming pool, PH and muriatic acid ... Reply with quote
Pepelos writes:

Quote:
It's no use to use muriatic acid (hydrochloric acid) because it's
dangerous.

It's not that dangerous, and it is used all the time for swimming
pools.

Quote:
I think you can use sodiun hypochlorite (bleach) as disinfectant.
Sodium hipochlorite is dissociating in water and results Free Chlorinne
(powerfull disinfectant agent).

You can use bleach, although most pool owners use an extremely similar
solution marketed specifically for pools (I don't know if it's really
any different from bleach--perhaps it contains fewer additives).

--
Transpose mxsmanic and gmail to reach me by e-mail.
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Gregg
science forum beginner


Joined: 12 Jun 2005
Posts: 33

PostPosted: Tue Jun 13, 2006 1:49 am    Post subject: Re: Swimming pool, PH and muriatic acid ... Reply with quote
mrdarrett@gmail.com wrote:
Quote:
Noproblem wrote:

snip



Oh, from your IP address, you're in Italy... no Home Depot there, I
bet.

Normally water exposed to air is somewhat below a pH of 7, because
water tends to dissolve acidic gases normally in air (carbon dioxide,
nitrogen oxides, etc.)

So, if anything, you're probably going to want to *increase* the pH of
your water. (Unless someone has already added a whole lot of stuff to
the water to increase the pH already).

Got any litmus paper strips to test your pool's pH?


My parents had a concrete pool and the pH tended to to be a little elevated.
It could have been an effect of the basic cement. - but I was never sure
of exactly what chemicals they were throwing into the water (or quantity).
My brother on the other hand had a vinyl liner and his pool tended to be
acidic.

Gregg
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Herman Family
science forum Guru Wannabe


Joined: 14 Jun 2005
Posts: 173

PostPosted: Tue Jun 13, 2006 3:55 am    Post subject: Re: Swimming pool, PH and muriatic acid ... Reply with quote
"Noproblem" <noproblem@NOSPAMMMMMMinterfree.it> wrote in message
news:448ddd96$0$1002$5fc30a8@news.tiscali.it...
Quote:
I bought a swimming pool with 24 cubic meters of water.

For lowering the PH of the water (I have to keep it in the range 7.2 -
7.6)
a specific solid product should be used, like this:

http://www.poolsinc.com/chem_bal3.html

I read somewhere that I could use the muriatic acid, that is cheaper.

Can you tell me the exact quantity of muriatic acid should I add to my
water
for decreasing the PH by 1/10?

I repeat: decreasing by 1/10 the PH for 24 cubic meters of water.

Thanks in advance.



In a word, no.

The amount of acid needed to reduce the pH depends on what pH you are
starting at, the buffer capacity and pKa of each ion in the system, and
where you want to end up.

To move from one pH to another, lets say lowering it, you add a bit of acid.
Lets say you are moving from 8 to 6. There are some ions which try to keep
it at 8 until you overcome them. Lets say that it takes a liter (that would
be a lot) to quench those. Once you do, the pH will suddenly drop to the pH
of the next buffering ion, perhaps at 7.4. You might spend a quarter liter
there, yet only a few ml to drop it another point. The difference between
the amount to go from 7.8 to 7.4 might be a few tenths or hundredths of what
it took to just move off of 8. It is very nonlinear and very dependent upon
what is in the water in the pool.

You are best off to go to the local pool supply with a water sample. They
will analyze it for you and tell you how much you need of their chemicals to
get the pool in shape. The alternative is to get perhaps a liter of pool
water, and a pH meter or some indicator (phenylthalein) , then slowly add
acid, carefully measuring how much it takes to get to the right pH.
Multiply that amount by the ratio of your pool volume to one liter (24000),
and you'll have the right amount. Add about 3/4 that amount, test the water
after it circulates for an hour or so, add half of the remainder, and again
test it. If it still isn't right, add the rest.

Michael
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Lloyd Parker
science forum Guru


Joined: 08 May 2005
Posts: 657

PostPosted: Tue Jun 13, 2006 11:28 am    Post subject: Re: Swimming pool, PH and muriatic acid ... Reply with quote
In article <8t5s829cfdlbb1pnc2tced7btp0vhiqpir@4ax.com>,
Mxsmanic <mxsmanic@gmail.com> wrote:
Quote:
mrdarrett@gmail.com writes:

So, if anything, you're probably going to want to *increase* the pH of
your water. (Unless someone has already added a whole lot of stuff to
the water to increase the pH already).

Chlorinated swimming pools almost always have a pH that needs to be
brought down. Usually chlorine (sodium hypochlorite solution) and
acid (hydrochloric or sulfuric) are added to the water periodically.

I'm not sure what raises the pH--the chlorine?

Got any litmus paper strips to test your pool's pH?

There are test kits available specifically for swimming pools. Some
people just throw chemicals in once a day or so, but it's best to
test.

Chlorine makes water acidic, by a disproportionation rxn:


Cl2 + H2O <=> Cl- + OCl- + 2 H+

Most swimming pools are treated with "dry chlorine", the OCl- ion in salt
form. This, hypochlorite is a weak base and so makes water basic:

OCl- + H2O <=> HOCl + OH-

It's the OCl- that's the disinfectant.
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Richard J Kinch
science forum beginner


Joined: 26 May 2005
Posts: 36

PostPosted: Wed Jun 14, 2006 6:22 am    Post subject: Re: Swimming pool, PH and muriatic acid ... Reply with quote
Mxsmanic writes:

Quote:
I'm not sure what raises the pH--the chlorine?

Sodium hypochlorite solutions (pool chlorinator or liquid bleach) contain
lots of of lye, makeing them heavily alkaline, which keeps the chlorine in
the solution instead of outgassing on the shelf.

Thus every dose of chlorinator, to avoid altering bulk pH, should get a
dose of protons, and muriatic acid is the cheapest source of protons.

http://www.truetex.com/poolcontrol.htm
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Richard J Kinch
science forum beginner


Joined: 26 May 2005
Posts: 36

PostPosted: Wed Jun 14, 2006 6:25 am    Post subject: Re: Swimming pool, PH and muriatic acid ... Reply with quote
Mxsmanic writes:

Quote:
You can use bleach, although most pool owners use an extremely similar
solution marketed specifically for pools (I don't know if it's really
any different from bleach--perhaps it contains fewer additives).

Pool chlorinator is typically twice as concentrated (12.5 pct) as household
laundry bleach (6.25 pct). Think of the volume of a laundry tub versus a
swimming pool, and how much you need to dose.

They are not stable. They all lose potency over weeks or months. Your old
bottle of laundry bleach is probably down to nothing in terms of chlorine.
It outgasses from the bottle and rots everything in the vicinity.
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Richard J Kinch
science forum beginner


Joined: 26 May 2005
Posts: 36

PostPosted: Wed Jun 14, 2006 6:28 am    Post subject: Re: Swimming pool, PH and muriatic acid ... Reply with quote
Herman Family writes:

Quote:
You are best off to go to the local pool supply with a water sample.

Bah. Get the phenol red indicator dye. If the pH is high, add a quart of
muriatic acid. Circulate and test again. Observe the pH change and dose
proportionately to your target.

You need to do this about once a week. You don't want to depend on the
pool store for testing.
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