Is it ok to use HCl to lower PH?

[ting]

I'm a new pool owner, now I only have a cheap 2-ways tester, which can only test TC and PH.
I just add all the water in to the pool few days ago and set the SWG timer to run for 9 hours a day (3 hours on and 5 hours off).

Today I just made the first test. The test result is 8.2 PH and 3.0 TC. I try to correct this by adding HCl (Hydrochloric acid) and re-program my SWG timer (from 9 hrs/day to 6 hrs/day). I will test it again tomorrow.

The pool shop, who sell me all the equipment, said I don't need to add anything other than HCl to lower PH.

I think I will going out to buy a better test kit, but I'm not so sure about the HCl, Is it ok to use?

My pool is outdoor and subject to direct sunlight about 8 hours a day.

 

[JasonLion]

We tend to use the name muriatic acid, since it is usually sold under that name, but technically it is hydrochloric acid. Exact same stuff, just two different names. Whatever you call it, this is the kind of acid we recommend for lowering PH.

 

[JohnN]

I think I will going out to buy a better test kit...

Yes, a good test kit is very important. The only choices worth buying are the Taylor K-2006, or TF-100. Both of these can be bought from tftestkits.net.

 

[Vette]

Beautiful pool! We recommend the TF-100 test kit, as John posted above.

 

[ting]

I just order the TF-100 test kit and the automatic stirrer, it might take few week to arrived.

Today I just test my pool again with the 2-way test kit. The PH still over 8.2 but TC is drop below 1.0.
I think I will have to add more HCl.

 

[chem geek]

A pool with multiple spillovers and with a saltwater chlorine generator will have a lot of aeration so a lot of carbon dioxide outgassing and that causes the pH to rise. You probably need to lower your Total Alkalinity (TA) which may help to reduce the rate of pH rise and especially the amount of acid you need to add. If you can get boric acid, then adding 50 ppm Borates can provide additional pH buffering. See Water Balance for SWGs.

 

[257WbyMag]

Yes, go ahead and add more HCl. You want your pH between 7.2 and 7.8.

 

[ting]

While I'm waiting for the TF-100 test kit to arrived. I call local pool shop and ask if they have CYA. They don't know what I'm talking about and ask me to hold the line. They return and told me that they have some kind of chlorine powder called "Trichloroisocyanuric acid powder 90%". Is this the CYA your guy talking about?

 

[JasonLion]

No, that is what we call trichlor.

CYA is sold under several names: cyanuric acid, conditioner, stabilizer, etc.

 

[Bama Rambler]

CYA is cyanuric acid or commonly referred to as stabilizer or conditioner. You really don't want to add any CYA until you're sure what the level is now.

 

[ting]

It seem like I can't find CYA here in Thailand. Try to call all the pool shop around and the answer is they don't know what I'm talking about. Try to call Chemical shop and found one have isocyanuric acid in stock, but they sell it in bulk of 25 Kilogram (50 pound).

So I'm thinking about using "Trichloroisocyanuric acid powder 90%" instate. Is that ok?

 

[JasonLion]

Trichlor also contains chlorine. Using enough to raise the CYA level a reasonable amount will raise the FC level rather too much. You can get around that by spreading your trichlor additions out across a number of days. It ends up being noticeably more effort, but it will work.