Swimming Pools in France

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raising total alkalinity on a bromine pool.

On a 30k gallon pool using bromine, my tester suggests total alkalinity is much too low.
The water is perfectly, incredibly clear ( at first glance this morning I thought it had all leaked out!)

The instructions are rather dog-eared but suggest it should be raised with sodium bicarbonate.....thats baking powder?

I can get 10 kgs on ebay for about 20 euros delivered. I asked how much it would be in the pool place but the guy seemed confused. Is that an outrageous thing to ask for in a pool shop?

The ebay stuff is advertised as food grade...is this the right stuff?


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Re: raising total alkalinity on a bromine pool.

As a chemist rather then a pool expert, Sodium Bicarbonate will raise the Ph. Whether this is food grade or not will not affect the alkalinity.

What I cannot understand is why you would use this rather than standard sodium hydroxide - which seems to be the basis of standard Ph+. The only thing I can think of is that bicarb might be more controllable than hydroxide - but if you are a long way off the target the objective is not to tickle the Ph to the right level.

A European Rahinja.
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Re: raising total alkalinity on a bromine pool.

I use bi-carb bought from ebay @ £14.99 for 10kg delivered free to a friend in the UK. It is very much cheaper than using a branded product from the pool shop & it does the job!

Graham (16)
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Re: raising total alkalinity on a bromine pool.

Dave what is the pool, tiled/plaster or vinyl liner/glass fibre?
If it's the latter then what is the level of the alkalinity?
Providing the pool water pH is reasonably stable then I wouldn't worry. The pool guides are written as if all pools are tiled/plaster which does need a decent level of alkalinity to protec the surface but that's not a requirement for liner or glass fibre. Because bicarb when in solution has a pH of around 8.2-8.3 that is too high so people add acid to lower the pH which becomes and endles cycle as the bicarb off gasses from the water quicker at a higher level causing the pH to rise and so it goes on. Having a lower alkalinity level can make the pH more stable from a pool perspective. For example my alkalinity level is around 37-45ppm and fine at that. It does take considerably less ph- to then get it to move because of the lower pH buffer which is what bicarb is used for but in our case the buffer is too high at pH 8.2-8.3.
Passivpool Energy "A++" rated Swimming Pools, the lowest running costs in the Universe.
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Re: raising total alkalinity on a bromine pool.

Thanks for the replies.

Its a "marbelite" finish, similar to concrete, which has been painted over with an epoxy resin paint, with a band of tiles around the upper 60cm or so. There is an infinity edge and shallow "beach" areas that are granite flagstones.

Typically I have forgotten the bit of paper with the chemical values on it, left it at the pool.

I uncovered it about 3 weeks ago and the water was green, but not too bad after the winter. Normal filtration, bromine and the hopping robot vacuum sorted it out in a couple of days. PH is stable and I have not needed to add anything else at all. The heating is running and its up to about 25 degrees already.

In previous years, the total alkalinity has always been at the low end of the acceptable range according to the tester, but this year for reasons unknown it seems to have dropped off a fair bit. Every year I reduce the level before winter by pumping into an underground storage tank and then pump it back in spring to get the level back to normal. There is a slight and unrepairable leak so there is a steady trickle of tapwater going in through the float valve.

With this type of pool construction, will low alkalinity risk damage or deposits on the surfaces? I would rather not get into a chemical war with it, having to adjust and readjust.....whether by luck or design (probably luck, the design of the pool seems terrible to my untrained eyes) it has always needed very minimal chemical intervention, with just a regular-ish 5kg bucket of bromine tablets into the distributer thing.


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Re: raising total alkalinity on a bromine pool.

Sodium Bicarbonate is Baking Soda not Baking Powder which is a mixture of Sodium Bicarbonate and Cream of Tartar.
"There are some causes worth dying for - there are no causes worth killing for" Albert Camus
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Re: raising total alkalinity on a bromine pool.

For swimming pools, it is more common to use sodium carbonate aka soda ash or washing soda to raise the pH. Sodium bicarbonate aka baking soda doesn't raise the pH as much unless the pH is quite low. Baking soda is normally used to raise the TA precisely because it doesn't raise the pH as much.

Soda Ash raises both the pH and the TA since it is technically the same as a combination of lye (sodium hydroxide) and baking soda (sodium bicarbonate). The reason that lye itself is not normally used is that it is fairly hazardous to skin and is very hygroscopic (absorbs water) so isn't a convenient powder as with soda ash or baking soda.

As was pointed out by Théière, higher TA causes more carbon dioxide outgassing which raises the pH. Low pH and higher TA result in more over-carbonation of the pool water. This is shown in <u><a href="http://www.troublefreepool.com/~richardfalk/pool/CO2.htm" target="_blank" title="http://www.troublefreepool.com/~richardfalk/pool/CO2.htm">this table</a></u>.
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Re: raising total alkalinity on a bromine pool.

I get our bi-carb from our local cooperative. 25 kg for 12.60€. It is what they call animal grade, so I phoned up the company's tech guys and asked what the difference was between animal and people grades. He told me "the packaging line". They are both the same.

The producer is Solvay, a French company and the tech guy I spoke to was very helpful. I have posted this info before if it seems familiar??


Never forget that you are unique, just like everyone else.
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