What is pH, and Why Does It Matter?
Learn the basics and get great hot tub chemistry. If you’re like a lot of new hot tub owners, the last time you had anything to do with pH was holding a strip of litmus paper against a lemon in middle school. You may have forgotten it all since, but now you’re realizing just how relevant that lemon experiment was to your new spa maintenance schedule. If you’re feeling in need of a pH 101 refresher then read on! No doubt you’ll remember more from your school days than you think.
What is pH?
Let’s get technical for a second.
In chemistry, pH is a scale used to determine how ‘acidic’ or ‘basic’ a solution is. In pure water there are an equal number of hydroxide and hydronium ions, making distilled water a completely neutral solution. In an acidic solution, however, (from black coffee to lemon juice to battery acid) the hydronium concentration is higher. In a basic solution (the likes of baking soda, bleach, and oven cleaner) hydronium levels are lower.
The pH scale ranges from 0 to 14, with 7 being the neutral point – this is what pure water measures. Each number on the scale represents a tenfold increase or decrease in the hydrogen concentration of the solution, so even a .5 shift along the scale can mean a huge difference in the pH of your water.
So what does this mean and why does it matter?
What pH should my hot tub be?
Although water has a pH of 7, hot tubs and swimming pools should fall around 7.4-7.6 on the pH scale … closer to the pH of human tears than to pure water. This makes hot tub water more comfortable to soak in, less likely to irritate skin and eyes, and allows your sanitizer to work to best effect – killing off any nasty bacteria that want a soak in your hot tub too.
While a safe pH range for your tub is 7.2-7.8, experts suggest trying to bring it in line with the recommended 7.4-7.6 to keep yourself and your family free from harmful bacteria and prevent burning eyes and skin after bathing.
What can happen if the pH is too high?
If you test your hot tub and get a pH result higher than 7.8, your water is too basic and at risk of causing scale to build up on your tub’s parts. These white, chalky deposits can feel like sand on the acrylic surface of your tub, or white flakes coming out of your hot tub’s jets. The result can be premature equipment failure and trouble removing the scale from your tub.
A high pH will see you churn through sanitizer more quickly, as the more basic the water, the more ineffective your sanitizer. At a pH of 8, for example, chlorine is barely 20% effective, and at 8.5 its effectiveness is under 10%.
This build-up of scale and impact on sanitizer effectiveness can easily lead to cloudy water, which is the bane of any hot tub owner’s maintenance schedule, and indicates things are just not right with your tub.
How can I lower my hot tub’s pH?
Lowering your tub’s pH can be as simple as adding some pH Down chemicals to the water, which most commonly use muriatic acid, also known as hydrochloric acid, to balance a high pH. But keep an eye out for the knock-on effects of using pH Down (aka pH Decreaser) chemicals: they can also make your Total Alkalinity levels drop. A vicious circle!
Keeping Mother Nature out of the spa can also help! Every little leaf and seed pod distracts your sanitizer, making it less effective and allowing the pH to continue its upward march.
What can happen if my hot tub’s pH is too low?
If your pH test strip comes back with a number lower than 7.2, your hot tub’s water is too acidic and can start corroding metal equipment in your tub and irritating your skin and eyes. It can also crack and de-laminate the acrylic shell, leading to unsightly scars and unhygienic crevices.
Water with a low pH level increases your chances of contracting hot tub folliculitis – essentially a bacterial infection of the hair follicles causing a nasty rash, and occasionally more severe symptoms.
It can also lead to the dangerous Legionnaires disease. This is caused by the bacteria Legionella which thrives in warm water, and particularly water with a low pH.
What causes low pH in my hot tub?
Low pH can be caused simply by enjoying your hot tub! Because human skin has a pH of 5.5, you’re likely lowering the pH of your tub every time you have a soak. Lotions, perfumes, shampoos, and detergents are also skillful pH downers, so having a shower before hopping in can go a long way toward preventing a pH plummet.
Again, the Total Alkalinity of your tub can play a huge part in a low pH reading, and low alkalinity is the more problematic of the high/low conundrum. Low TA can lead to extreme fluctuations in pH, which can have major effects on your hot tub’s appearance and water health.
The use of sanitizers and other spa chemicals can also throw your pH into a spin, so be aware of how much you’re using, and whether these additions might be impacting your pH.
How can I raise my hot tub’s pH?
Raising your spa’s pH is easy with pH Up chemicals – also called pH Rise and pH Increaser. These are most commonly made of soda ash (sodium carbonate) and lift the pH of your tub, until it reaches that 7.4-7.6 pH safe zone. Getting this balance right in the start-up phase is crucial, but pH is one of the things you’ll need to check regularly – at least 2-3 times per week.
Want to lift pH but not interfere with your TA levels? Magnesium oxide is your go-to in this case. Although it will raise your TA a little, it’ll be nothing compared to soda ash options.
If it’s your TA that’s low overall, Alkalinity Plus can help. But take care when you use it and test your water again after 6 hours – the addition could cause your pH level to rise too much.
If you’re still not sure what this pH business is all about – don’t panic! Carefully read up on establishing your new tub and try and get things right from the outset. From there your pH balancing act will involve a little knowledge, some trial and error, and a healthy dose of luck!
You’ll be a pH pro in no time, we guarantee it!