Spa pH

Calendar icon
Folder icon

Why the pH of your Hot Tub Water Matters

The pH scale defines the level of acidity or basicity of water. It ranges from 0-14, with zero being as acidic as you can get. On the opposite end of the scale, fourteen is as basic, or alkaline, as possible. Neither is good for pools or hot tubs, with a general recommendation of slightly basic as optimum. 7.2 to 7.8 is considered ‘balanced’ and in the ideal range of the spectrum. Too many people with hot tubs and swimming pools fail to keep their pH in the acceptable range. They simply look at the water and if it looks clear and clean, it’s time to jump in. Simply put: wrong! Let’s look at why.

Wasting money.

This is probably more significant in swimming pools than in spas and hot tubs. Water that is acidic will burn through chlorine at a much faster pace than in balanced water. Few use chlorine in hot tubs except for quick shocks or boosts to other sanitization systems. It simply burns out too quickly in hot water. Bromine is more stable in hot water but will still have a shorter life span than in balanced water. However, with hot tubs, a bad pH can lead to far more costly expenses.

Damage to plumbing.

The water delivery system that ultimately leads to the jets is a hidden system, encased inside the cabinet. Out of sight, out of mind. But if left unbalanced, acidic water will gradually eat away at the flexible piping. It will get brittle and will become more susceptible to leaking. Plus, glue joints will be compromised and could lead to lines popping off at the fitting.

Damage to the motor, pump, and heating element.

Water is pushed through a motor via an impeller. This impeller is attached to the motor shaft, ending at the pump housing’s ‘wet end’. There is a mechanical seal, commonly referred to as the shaft seal, which isolates the motor from the pump housing. Working properly, it is a closed system with no leakage between the two components. However, acid water will gradually eat away at the seal, causing a leak to develop. The shaft will start to corrode, making it difficult to successfully replace the shaft seal. This leak also exposes the motor’s front bearings to corrosion. Corroded bearings allow the shaft to wobble ever so slightly. In short order, the wobble will get worse, and a loud screeching noise will develop. I’m talking real loud. A long time ago, I had bearings go out and heard the motor screaming a half-mile away. Fortunately, my neighbors had a sense of humor. I think. Ultimately, the motor was shot. The culprit? Nobody to blame but myself.

Even the best heating elements are not impervious to damage from low pH. I’ve seen elements that have been destroyed quickly from acidic water. An affected element doesn’t just heat slower. It fails completely. So, you had a tough week and want to get in the hot tub to relax. You remove the cover, start to get in, but are stunned by cold water. No heat. Don’t allow this to happen.

Damage to jets.

Some manufacturers still use jets that spin or pulsate the water via small ball bearings inside the jet housing. They allow the spinner to rotate freely, providing a therapeutic and really neat sensation. Like the seal set, these bearings are negatively affected by low pH. This happened to me a long time ago. I got in my tub and felt little hard pellets in the footwell. My first thought was that neighbor kids had shot BBs into my tub when I wasn’t home. That idea lasted a few seconds until I realized they were stainless steel ball bearings. Yep—bad pH had been the culprit. The jets still delivered water but didn’t spin. I replaced them at a pretty hefty price.

More common these days is the simple deterioration of the jets themselves. Many still rely on small tabs to lock the jet in place. Acidic water will eat away at the tab and the jet will continually pop out. It will need replaced. And if you have jets with metal trim, watch how fast that trim deteriorates in low-pH water.


At the heart of the discussion, who wants to sit in an acid bath? It’s not healthy and can be highly irritating to your body. Skin will tingle and not in a good way. Eyes and nostrils burn. Total discomfort ruins the whole hot tub visit.

I know what some are thinking. “My pH is just a little low. I’ll fix it…tomorrow.Well, technically, tomorrow never gets here. Plus, just a ‘little low’ is misleading. The pH scale is exponential. Each whole point on the scale represents 10-times the difference between levels. For example, a pH of 6.0 (highly acidic) is 10-times more acidic than 7.0. A pH of 5 is 10-times more acidic than 6.0 and 100-times more than 7.0. And so, you test your water and it comes up at around 6.7. That is more than a little acidic. Adjust it…today.

What about high pH?

As mentioned, a slightly alkaline level is desirable when falling in the 7.2 to 7.8 range. However, while not as harmful as low pH, high alkalinity has its own set of issues. Firstly, a high alkaline level can force dissolved solids in the water to come out of solution. This can cause scaling and clogged filters. Clogged filters reduce flow and puts strain on the pump motor. Secondly, water gets murky or cloudy. That’s the dissolved solids that haven’t taken up a new home in the filter, plumbing lines, or on tub sides. Lastly, the higher the pH, the more difficult it is to lower it. Alkaline content serves to ‘lock’ in the pH. So, you add pH decreaser to reduce the pH and nothing happens. You dose again. Still, nada. You continue dosing until the pH starts to drop. Then suddenly, the bottom falls out and now you have a low pH problem. Jeesh!

It's easier to adjust pH when you only need to make small adjustments. The solution is simple. Use a home test a couple times a week and dose accordingly. If you use the tub every day, it only takes seconds when using litmus-strip tests.

In summary…

Old Ben Franklin said it best: “An ounce of prevention is worth a pound of cure.” Keep a close eye on your pH and adjust accordingly. A little diligence now will likely save you hundreds of dollars and tons of aggravation down the road. Eastgate Pools & Spas has a great selection of hot tub chemicals needed for keeping water properly balanced. If you live locally, feel free to bring us a water sample. Our knowledgeable experts will be happy to double-check your results and offer advice if you are having issues.