Hot Tub Water Chemistry 101: PH Balance

I have been testing a lot of hot tub water this past week at our store and I realized that we get a lot of questions about PH, and why it fluctuates so greatly in a hot tub.

As briefly as I can I will try to lay out some reasons why PH, which is one of the most importatnt levels in hot tub water chemistry, is not so stable.

PH is affected By Everything!

The first thing to understand about PH is that everything that goes into the water has it’s own ph level. Bromine tablets for example can have a PH anywhere for 6.5 to 8ppm (parts per million).

The optimum range for PH in spa water is 7.2-78

Spa shock, typically in the form of Potassium Monopersulfate has a very low ph and most spa owners use that after each use. Those are just 2 chemicals or products that get added to your hot tub regularly that effect the PH levels.

Some chemicals can cause PH to go up, some can make it go down, and these levels are generally not printed on the back of the bottle.

Bubbles Make PH High

If you have owned a hot tub for any amount of time and been regularly testing the water you may know that a lot of times your PH is high, in fact most of the water tests I do on a weekly basis for spa owners have a ph of 7.8 to 8.2.

So what is the reason for this constant increase? A big cause of this rise in PH comes from the main function of the hot tub….the jets!

Thats right the jets themselves cause the PH in your spa to go up. This is just a matter of basic chemistry, aeration of a solution causes a rise in PH. A hot tubs job is to create turbulance in the water, and we have air valves that add oxygen to that aeration.

Without getting too geeky, what is happening is the carbon dioxide that gets added into the water off gasses into the air taking with it some carbonic acid. Whenever you remove acid from a solution the PH will rise.

This process is happening all the time in a hot tub environment and there is really nothing we can do about it, other than perform regular water tests and adjust as necessary.

How important is proper PH

The PH level in your hot tub has a direct effect on how well chlorine or bromine can sanitize the water. Has the PH moves out of the ok zone (7.2-7.8) you need more chlorine or bromine to sanitize the same amount of water.

For the sake of simplicity I tell my customers to test and adjust their hot tub water chemistry once per week. In a perfect world you would do this daily in order to keep the water perfect, but in my experience this kind of obsessiveness does more harm than good.