pH Minus Question

[Simon]

I have a new pool with a Chlorine Liquid (Javel) auto doser and pH minus doser.  I use Javel lfrom the local brico (rather than the Chlor from the local pool merchant) as it is half the price.

The pH minus (that came with the pool and was a solution of Sulphuric Acid according to the label) has now run out and after flushing the doser with water I now use 33% Hydrochloric Acid (from the Brico and again half the price of the pool merchant).

With my long ago O-level chemistry I believe this will be OK.  Can anyone confirm that using Hydrochloric acid will be OK and is the same as pH-.

Tks

 

[Poolguy]

Simon

You were not specific on what Auto Doser you have. (using vlaves or pumps to inject.

Certainly, I prefer to use Sulpuric acid exclusively, the reason for that: is safer because there are little or no fumes(nasty)

Also because it is also purer- there is a lot of residue in hydrochloric acid, the processing is very cheap as is the price.

and because if you have certain types of injection then the residue from the hydrochloric can build up and create a blockage, its just another problem to watch for which can be avoided by using a better quality of acid.

If there is any choice for you I would suggest either stick to Sulphuric acid, or use sodium bisulphate(dissolved and strained), and only as a last resort or for emergencies then Hydrochloric acid(heavily diluted say 5:1).

All that being said, there is little chemical reason why hydrochloric cannot be used except that it seem to be more copatable with salt electrolysers and actually helps the production of chlorine, but you will have no difficulty to manage the pH using this product.

At the same time, make sure that you keep your Total Alkalynity and Calcium hardness under control other wise the whole system will go a little mental.

Contact me if you need any help or for any supply difficulties (chemical and/or testers.)

Andrew

[Simon]

I have peristaltic pump system.  Thanks for your response - will probably change back to Sulphuric Acid on my next visit in 3 weeks time.  HCl does smell rather nastily!

How do I manage Total Alkinity?  The pool appears to be sparkling, although my CoolPool Tester does show low for Total Alkinity and I am using a lot of Javel when the pool is open.  Should I put Sodium Bicarbonate in and how much per m3?

Also what is the right level for Chlorine as ppm?  Is 3 - 4ppm about right?  Coolpool tester has shown around 2 - 5 ppm when testing over a period of 3 weeks (when we used 20L of Javel).

Rgds   

 

[Poolguy]

Simon

I suggest you call me for more detailed advise.

I am surprised that the poolshop who installed your controller did not help you with more backup - chemicals and advice.

Anyway, a level of 1.5-3ppm of chlor is fine in a stabilised pool, 3-5

is too high and unnecessary unless you are running very high

temperatures.

I suggest that you get the machine recalibrated to reduce its

consumption which is costing you too much money and you will end up

chasing your tail to balance it all. More chlorine, more acid, then

more Bicarb and round again.

What brand is the controler?

If you cool Pool tester is ging you a low TAC reading the you'll need

to add Bicarb soda, but to estimate the quantity I'll need to know the

volume and the TAC reading.

I am not surprise that you have nice water... your munching a lot of chlorine.

If you change your filter sand to zeolite then you will get a much more stable TAC 80-130ppm is ideal.

Andrew

[phil]

Hi Simon,

Yes, you can use either acid. Having used Hydrochloric for many years in our commercial pools, I have recently experimented with Sulphuric with good results. The fumes from Hydrochloric are very obnocscious. Also Hydrochloric is very similar in apearance to Hypochlorite (which is, I assume, what you are using for disinfectant under a trade name?) presenting the serious hazard of mixing them by accident - something of course you must avoid at all cost due to the liberation of Chlorine Gas which is lethal.

If you are using Sodium Hypochlorite, I am surprised you are not using a 'stabalized' disinfectant if it is an outdoor pool? Unless you are adding stabalizer seperately? Could do with a little more info really Simon.

Dependant on the Alkalinity of your water, another possibility is the use of Co2 - although I am not sure how feasable this would be in a private pool - cost and supply etc.Again I am assuming this is your own pool?

When using Sulphuric acid it may be wise to check the Sulphate level in your water occasionally (needs to be below 360). Sulphates can attack your pool fabric - grouting particularly

Regards

Phil

Pool Plant Man.

 

[buckdendave]

Not all will agree with me but I think hydrochloric acid is better than sulphuric - at least it is from a chemistry point of view.  There are various reasons - firstly, and I think that this is the most important - chloride salts are invariably more soluble than sulphates - so there is less tendency to generate a crust around the water line.  Secondly, because it's a better buffer with a chlorine sanitised pool.  Then there is the cost.

Against these things I have to agree that the fumes are worse with hydrochloric acid than sulphuric, and also that those used to handling so-called "dry acid" may be more comfortable with using sulphuric. 

David