Hello:
We run two pools on Hypochlorite in the Philippines. Water temp. constantly around 30° Celsius. The chlorine disappears nearly quicker than it can be replenished, white dust everywhere even now that we don´t throw the granulate directly in the water anymore but in a sock placed in the water or skimmer, scale is forming and the pH is always around 7.8, nearly impossible to lower it with dry acid.
There are many reasons that chlorine demand could be too high which is why we need your pool's water chemistry numbers to know. One possibility is that there is little or no Cyanuric Acid (CYA), aka stabilizer or conditioner, in the water. If the pool is exposed to direct sunlight, then without CYA in the water half of the chlorine can break down from the UV in sunlight every 35 minutes. Another possibility is that the CYA level is high and the FC too low relative to the CYA level. In this case, the chlorine demand could be from nascent algae growth, even before the algae has become visible (i.e. water dull then cloudy then green).
The pool dealer told us to use Guardex conditioner, Quote: "This chemical, when added to your pool water with the Niclon Chlorine, would be similar to the effect an organic chlorine would produce".
The word "conditioner" most likely refers to Cyanuric Acid (CYA). So your dealer is assuming that the problem in your pool is that you never added CYA and have never used stabilized chlorine. Though this may be true, testing your pool water chemistry, including CYA level, will let us be more certain about that.
The question is now: 1.: To have the Hypochlorite last longer I neeed CYA. Will it then be really the same as stabilized Chlorine?
IF you don't have any CYA in your water AND your water is exposed to direct sunlight, then you definitely need to add CYA to the water in order to prevent sunlight from breaking down chlorine quickly. Even if your pool wasn't exposed to direct sunlight, it's still a good idea to have some CYA in the water to prevent the "active" chlorine from being too strong. Yes, having CYA added to the water along with unstabilized chlorine is IDENTICAL to using stabilized chlorine in the water, ignoring the effect on pH from using different chlorine sources (e.g. Trichlor pucks are very acidic).
But to get rid of the scaling I better don´t use Hypochlorite, right? If I use stabilized chlorine which should dissolve completely there is really no white dust and scaling anymore? But then the CYA will get too high over time. If I use pucks the same problems, I would like to know how long a 3" puck lasts in the skimmer on lets say 10 hrs pump run time?
Using hypochlorite sources of chlorine do not cause scaling. Scaling is caused by incorrect water balance and this is a combination of pH, Total Alkalinity (TA), Calcium Hardness (CH) and to a lesser extent Cyanuric Acid (CYA) and temperature. This is, again, why we want to know your water chemistry parameters.
For example, if your TA level was too high, then that would tend to make the pH of the pool rise so that combination plus a possibly high CH could lead to scaling. One solution to this is to lower the TA level since that helps solve the scaling problem directly and also slows down the rate of pH rise. Again, we need to know your water chemistry parameters in order to give you the proper advice.
At this point, if you were to use stabilized chlorine, it would not solve your scaling problem unless the Trichlor puck usage was acidic enough to bring your pH down. Since you are having trouble bringing it down with dry acid, the Trichlor pucks probably wouldn't be enough to help either. The problem with the pH staying high is most likely due to the TA being too high, but again...well you get the idea.
How about using an SWG in CYA stabilized water, no fine dust and scaling and rising pH anymore?
An SWG pool does typically have CYA in the water, usually a lot of it to minimize chlorine loss from sunlight so one can keep the SWG turn on time as short as possible. However, SWG pools typically demonstrate a rise in pH, though that can be minimized through techniques described in
this post in the Pool School. However, it should not at all be necessary to go to an SWG to solve your problems with your pool. The SWG would mostly just provide more convenience in not having to add chlorine regularly -- it is not necessary to keep a pool free from algae nor to prevent scaling.
Ideal seems to be liquid chlorine together with 25 ppm CYA. Why there is no 100% liquid chlorine available?
As Jason pointed out, the chemistry prevents their being a safe form of 100% chlorine. The 100% form of chlorine is chlorine gas and would be unsafe for residential customers to use. It is sometimes used in some commercial environments or with a few pool services, but it is less common. There is absolutely nothing wrong with using chlorinating liquid (or bleach) in a pool that already has CYA in it. In fact, it's what most people on this forum do (unless they have SWG pools) and have minimal problems with their pools. As for the CYA level that is best to use, that depends on your situation, but typically it's 30-50 ppm unless you've got a lot of strong sun in which case a higher CYA level (but not more than 80 ppm) is sometimes used.
This chart in the Pool School shows the FC level needed at various CYA levels.
The same with acid, why there is no 100% acid? Is the dry acid more enonomical than bleach? How much 100% acid makes 5 Kg of dry acid?
The dry acid is nearly 100% pure substance though there is no such thing as 100% pure acid since the "acid" portion (which is positively charged) needs to be attached to something (negatively charged). Dry acid is usually 93.2% sodium bisulfate. However, since this builds up sulfates in the water, we sometimes recommend using Muriatic Acid which is usually 31.45% hydrochloric acid (full-strength). This is very strong and often fumes and is irritating, so one can get half-strength that fumes less. Dry acid and full-strength Muriatic Acid are roughly the same acid strength by volume.
Acid and bleach are two completely different things. Bleach is the same as chlorinating liquid except it's not as concentrated so it is a source of chlorine.
I don't understand your question regarding 100% acid equivalent of 5 Kg of dry acid. 5 Kg of dry acid is equivalent to 3.9 liters of full-strength Muriatic Acid and is a LOT of acid. You would never add that much to a pool unless the pool were at least 100,000 liters (26,400 gallons) and you wanted the pH to drop significantly (say, for the procedure that lowers the TA).
Alum potass filter aid which seems to be readily available here since it is used as a anti-transpirant: How introduce it in the water, dissolve first or in the skimmer, how much to use per 5000 Gals?
Alum is usually a flocculant that consolidates particles and has them settle to the bottom of the pool where you need to vacuum-to-waste to remove them. It sounds like the particular product you refer to is more like a clarifier that consolidates particles to have them get trapped more readily in a filter. These products are not usually necessary if you are properly maintaining your pool. Please tell us more about your pool (such as pool size, filter type, etc.).
Hope for a qualified answer out here.
As Jason said, we can give you much better advice if you follow the guidelines in
this post and give us more information about your pool and equipment characteristics and its water chemistry values.
