Stubbornly low pH

[LMH]

HELP PLEASE!  I have a small 2-person hot tub. The water is only 6 weeks old and my pH/alkalinity is out of whack. I first adjusted the alkalinity down and was barely able to get it to the high end of the good range. Now I am trying to raise ph and it won't budge but is raising the alkalinity again. The pH remain between 6.2-6.4. Is it a lost cause? Do I need to change out my water?  My local hot tub store guy said it was likely detergent that upset the ranges because I also have foam and that I need to change my water.  I'm using Freshwater Brand pH/Alkilinity Down = sodium bisulfate and pH/Alilinity Up = sodium bicarbonate. 

Thank you in advance for any advice you can give me.

[LMH]

Btw I did get rid of the foam and alkalinity is now at 120. 

[MPurcell]

I can help you with your water chemistry, but I will need more information than you have given so far.

You should normally expect to change the water in a hot tub about once every 3 to 4 months, so 6 weeks would usually be too soon. That would depend on what you have put into the water up to this point.

Sodium bisulfate, also known as dry acid, will reduce pH and Alkalinity. Sodium bicarbonate, also known as baking soda, will raise alkalinity, and also raise pH to a degree. So what you describe doing above would have reduced the pH as you brought the alkalinity down with sodium bisulfate, and then increased the alkalinity as you brought the pH up with the sodium bicarbonate. So what you experienced was expected behavior for those two products.

You can use sodium carbonate, also known as washing soda, to raise pH without changing the alkalinity very much. Alternatively, you can use sodium tetraborate as in 20 mule team borax to raise pH without changing the alkalinity very much.

You can't effectively balance your water without knowing accurately what you are doing. How are you testing the water? Do you have your own test kit, or are you using test strips, or are you relying on the pool store's testing? I strongly recommend doing your own testing with a good quality test kit, in order to get the results you really want.

Are you using chlorine or bromine, and what sanitizing method are you using?

What have you put into the water from fill up to this point?

A description of your tub would also be helpful.

[Cusser]

Agree: sodium carbonate to raise pH, add in 1 ounce increments..  Sodium bicarbonate works once you get closer.

Chlorinating and brominating tablets will tend to lower water pH.  It's in plaster pools that the plaster causes pH to rise so acid needs to be added.