reducing the ph in a pool

[osie]

Hi All

I have always used the powder ph- to reduce the pools PH.  It sits for a couple of days after which it is ready for use.

If I am correct, javel is also an option.

And, I have just discovered L'acide chlorhydrique (as I did some tile cleaning).

So, my question is what are the pro's and con's of these methods to reduce the ph.

It seems L'acide chlorhydrique is cheaper and possible takes effect quicker.. but I dont really know.

osie

[Théière]

Hi Ossie,

You are correct these generally available products are much cheaper than pool shop chemicals, Pool shops often tell you not to use them as their profits will drop (oops sorry you will do irreparable damage).

Javel is Chlorine which is used for sanitising the water and has a PH of 11-12.

Hydrochloric acid can be used to lower your PH.

Pros cost.

Cons handling reasonably dangerous acid (fumes and spills). Do not pour strong chemicals into the skimmer, pour slowly in front of the return jets. Do not mix acid with javel or dangerous chlorine gas will be given off.

[osie]

Thanks Teapot...

So, that means if I always have a high ph water then javel is not the right chemical to use for me?...

Also, am i correct in saying that my cement acid is Muriatic acid which is not as good as Hydrochloric acid but works too.

Thanks

osie

[Théière]

Osie, need to put in a distinction here, Javel is chlorine and you need some of that in your pool to keep it healthy about 1ppm.

To keep the PH in the range PH7.2-7.6 you would normally need to use a PH reducer which is an acid. Muratic acid is hydrochloric acid but an American name, hydrochloric acid like cement/brick cleaning acid (10%) and the full strength Hydrochloric acid (36%)  are the same just different strengths so you would need to use more of the 10% to achieve the same PH reduction as the 30%.

Safety equipment is a must when handling, goggles, activated charcoal mask and gloves should be the norm. 

[osie]

Cheers teapot..

So whether it be chlorine tablets or javel... they all increase the ph of the pool... c'est la vie.

so to reduce the ph one needs to use some form of Hydrochloric acid or the ph - stuff.... the purer the acid the less you need.

All the above is of course in laymans terms...

it is good to know that I can stop buying the ph- as it is quite expensive...

thanks

osie

[Théière]

Yep that about covers it. The multi action tablets however are blended with acid in them so they keep the pH pretty stable, sounds good yes? The problem is the multi action tablets also contain cyanuric acid (CYA) to protect the chlorine from the UV of the sun, you need some CYA but over a season that level builds up too high so you will have to replace all/some of the water (additional cost) Some multiactions contain other things like copper (seen as little blue flecks) this too can build up in a pool and potentially stain or in some cases turn blonde hair a green tint.

[osie]

okay... so unless you dont have a pair of googles... the preferred solution is the the hard core acids...

What I imagine I will do from now on is to have an automatic galet doser keeping things at a minimum but to make adjustments using hydrochloric acid.

Thanks again for the help

osie

[Théière]

Gallets won't really need PH adjustment as they are already acidic as my post above (multi action tablets) you could get a small chemical pump to take care of the javel dosing and the PH adjustment so that would pretty much look after that side for you but you would still need to test the water as a fail safe each week minimum.

[chem geek]

The point that is missed here is that the use of hypochlorite sources of chlorine (chlorinating liquid or Javel, bleach, Cal-Hypo, lithium hypochlorite, and a saltwater chlorine generator) all raise the pH upon chlorine addition BUT the pH gets lowered back down to where it started as the chlorine is used because the consumption/usage of chlorine is acidic (technical details in this post).  The net pH rises only a small amount from the "excess lye" in the products.  Most pH rise that is seen is caused by carbon dioxide outgassing because pools are intentionally over-carbonated in order to provide a pH buffer and to protect plaster surfaces.  It is higher Total Alkalinity (TA) and water aeration that causes the pH to rise, not the use of hypochlorite sources of chlorine.  [url=http://richardfalk.home.comcast.net/~richardfalk/pool/CO2.htm]This chart[/url] shows how over-carbonated water is with respect to equilibrium with air and you can see that lower pH and higher TA are more over-carbonated.

So when using Javel, you should have the TA be no higher than 80 ppm or even lower if the pH tends to rise too much.  If you have to lower the TA a lot due to lots of aeration from waterfalls, spillovers, fountains, splashing, etc. then you can use 50 ppm Borates in the pool as an additional pH buffer (see [url=http://www.troublefreepool.com/so-you-want-to-add-borates-to-your-pool-why-and-how-t4921.html]Adding Borates -- Why and How[/url] for more info).  If you have a plaster pool, then you can raise the Calcium Hardness (CH) to compensate for the lower TA so that plaster is still protected (i.e. so that the saturation index is still near zero).  Note that to lower the TA efficiently you combine acid addition with aeration all done at a lower pH (see [url=http://www.troublefreepool.com/pool-school/lowering%20total%20alkalinity]Lower Total Alkalinity[/url]).

I use only 12.5% chlorinating liquid in my 16,000 gallon pool and only have to add a few cups of acid once a month.  I have a pool cover that reduces the amount of outgassing (though the pool is used for an hour or so every day), but others with uncovered pools can have fairly stable pH by keeping the TA lower.  Also note that the rate of pH rise slows as the pH is higher so having a 7.7 target instead of 7.5 or lower can also help in some cases.  Also note that for newer plaster/concrete pools, the curing process causes the pH to rise a lot, especially in the first month, but this process can continue on at a lower rate for up to a year and that requires acid addition (i.e. a lower TA won't eliminate needing to add acid to compensate for curing of plaster).

[Polly]

Osie, is this the pool your guests use that you are talking about here?

If it is, and you are worried about or don't understand the chem balance you should perhaps be seeking professional advice on-site, and maybe contact the DDASS in Cahors for confirmation that all is OK for your guests. You don't want anybody to fall ill....

[osie]

Hi Polly

Thanks for the advice... but I do not have any problems per se, actually, the pool works very well as I have got it set up... and in any case the DDASS(in Rodez) pop round twice a year.

What interests me is to refine my existing way of doing things to save time, money, effort and to make people as happy as possible.

Also, the great responses from the experts to put knowledge to the tasks that I do... the how it all works.

If you have a look at the original post.. you will see it asks about a new material that I have not yet used in the pool, not about how to balance the pool.

Thanks

osie

[Théière]

Helpful information re your DDASS visits and Chemgeeks post. There is a cost/quiet life balance thing here then. I don't think the DDASS would take to a galet dispenser although you never know. The problem with using galets is the build up of the CYA and possibly copper which using the plain liquid javel and acid would solve. There are small dosing pumps available to semi automate the process depending on budget these vary in complexity.

A basic small unit like this one up to more sophisticated versions dependant on budget of course but compared to draining down and re-filling with too much CYA build up these little units should soon pay for themselves

[Polly]

Hi Osie

I hope you didn't mind me raising the issue, with your reply anyone reading the thread will benefit from your tech questions and now the DDASS angle too

Here's to a good season, with lots of happy guests!

[osie]

Hi Polly

Not at all. I hope it will help somebody.. but the responses that really answered my question were those from teapot and chemgeek...

It is quite easy to balance a pool, but the understanding behind  it is bit of a black book and the black book is needed if all goes belly up and start turning green.

I am also sure that chemgeeks responses would not be part of your average 'how to maintain a pool' knowledge.

Thanks

osie

[osie]

Hi Teapot..

Is that a dosing pump that you recommend.. can you give me a link or name to look up.

Thanks

osie

[Théière]

Yes Ozie thats a Seko pump in the picture, they have various versions. That is one of their small single untis, they come with a Ph probe and all the required parts. They have a similar chlorine version with a timer attached so you can set the pump duration based on the usual chlorine usage.

[chirpy]

I remember a few years ago being told to use sulphuric acid and not hydrocloric acid....dont remember the reasons ....any comments?I have been using this recommendation ibstead of the expensive ph-ve  powders.