Properly maintaining the pH and alkalinity levels in your hot tub is essential for ensuring a comfortable and safe soaking experience. It can also help extend the lifespan of your hot tub and its various components.
In this guide, we will explain what pH and alkalinity are and how they relate to your hot tub, as well as provide step-by-step instructions on how to properly test and adjust these levels. Let’s get started with a quick-fix guide to the most common balancing issues of pH and alkalinity.
Quick-Fix Guide for Common pH and Alkalinity Issues
Properly maintaining alkalinity and pH levels in your spa is crucial for ensuring the cleanliness and health of the water. Improper alkalinity balance can affect pH readings, cause skin irritation, and even damage the hot tub itself and its internal components.
If your hot tub’s acidity or basicity gets out of control, it can be a long road to bring the levels back to normal. Let’s take a look at some common pH and alkalinity issues that hot tub owners face.
pH and Alkalinity Are Both Low
Increase the pH and the Alkalinity by adding a suitable amount of spa pH increaser, such as sodium bicarbonate.
pH and Alkalinity Are Both High
Reduce the pH and the alkalinity by adding a spa pH reducer acid such as sodium bisulfate or muriatic acid.
pH and Alkalinity Are Both Stubbornly High
Stubbornly high refers to conditions when it seems that no matter how much pH reducer you add, the test strip shows little or no change. This is often a sign that you have tried to adjust the pH before the alkalinity, and now your readings are all over the place.
Resolve stubbornly high pH and alkalinity with the following:
- Double the amount of pH/alkalinity reducer (sodium bisulfate) you would normally use.
- Wait 10 minutes for the pump and water jet to mix the solution into the water.
- Retest.
- If the result is still abnormally high, repeat the above.
pH Is in Range, Alkalinity Is High
- Add more pH reducer.
- Run the pump for 30 minutes and retest.
pH Is in Range, Alkalinity Is Low
Add a small quantity of alkalinity increaser and run the pump for 30 minutes before retesting.
pH Is High, Alkalinity Is in Range
Add a small quantity of pH reducer and retest after running the pump for 30 minutes.
pH Is High, Alkalinity Is Low
1. Run the pump and add your pH reducer.
2. Test the pH every 30 minutes and keep adding until the alkalinity is in range.
When adjusting and testing the pH, you want to have your air blowers turned off as the bubbles will increase the pH. Also, try to avoid pushing the pH level above the ideal, as this will make the process of balancing out the acidity much harder.
pH Is Low, Alkalinity Is in Range
You can use a pH increaser without sodium bicarbonate. When adding a pH increaser, turn on all the jets and blowers. Wait 30 minutes before adding more pH increaser, and test each time.
pH Fluctuates Greatly
Fluctuations are often down to low alkalinity, and this problem can be fixed with this method:
- Add an alkalinity increaser such as sodium bicarbonate in small amounts until the issue stops.
- If this pushes the pH out of the suitable range, you can bring it back with the above steps.
6 Simple Steps to Adjust the Alkalinity in Your Hot Tub
The alkalinity will often go up when you top up your spa with water from your hose if you have hard water and down if you have soft water. Ideal spa alkalinity is between 80 ppm and 120 ppm, though the amount of product you need to add will depend on the water capacity of your spa.
An alkaline spa will go cloudy if the levels are allowed to rise above a pH of 7.8. This can lead to deposits of calcium on the pipes and pumps and fade any patterns on the edge of the spa.
A high pH will also reduce the effectiveness of the chlorine or bromine you add to the spa. Chlorine is vital to disinfect the tub to prevent disease and bacteria from transferring from person to person in the water. At a pH of 8.0, the chlorine is less than 20% effective, and less than 10% effective when the pH goes above 8.5.
Most modern spa treatment products try to adjust both the pH and the alkalinity of your water at the same time. But you can still buy products that treat pH and alkalinity independently. A mixed product is easier to use in most cases, rather than trying to balance the pH and alkalinity yourself.
You can adjust your spa’s alkalinity with the following steps:
- Turn off the blowers and run the water pump.
- Check the pH and the alkalinity of the water to see if you need to reduce or increase the alkalinity.
- Use your readings along with the spa’s water volume to calculate the amount and type of product you need to use.
- If you need to increase the alkalinity, add a half-ounce (14g) of pH increaser. If you need to lower the pH, then add a pH reducer.
- Leave the pump to run for 5 minutes and test again. If the pH is far below the recommended level, you can start by adding a full ounce (28g) of pH increaser.
- Repeat the steps until you are in a suitable pH range.
Note: – An older neglected spa may have deposits of calcium stuck to the inside of the pumping system. Calcium will fight your efforts to balance the alkalinity as chunks flake off and dissolve in the pH reducer. It may be faster to rinse and drain the hot tub and then refill it with fresh water.
6 Simple Steps to Adjust the pH in Your Hot Tub
When adjusting the pH of your water, you should begin with getting the alkalinity within the correct range to avoid a yo-yoing of levels. Follow the procedure below to stabilize your spa’s water and obtain the optimal pH level.
Step 1 – Turn the Pump On
The chemicals that you add to a spa will sink or float in the water, causing concentrations to appear higher or lower than the average. Turn the pump on for a few minutes before testing. The pump helps to mix the chemicals back into the water, which will give you a better reading.
Note: Turn the blowers off, as the air bubbles will raise the pH and give you misleading readings.
Step 2 – Test
Use your test strip and reference card that came with it to check the pH, chlorine, alkalinity, and bromine levels. Take an elbow-deep sample from the middle of the spa for the most accurate readings.
The optimal pH range is between 7.4 and 7.6. Extreme highs or lows of alkalinity mean that you have used too much sanitizer.
Step 3 – Measure Before Adding
The pH scale is logarithmic, which means that each unit of pH represents a tenfold difference in acidity or basicity. For example, a pH of 7 is ten times more basic than a pH of 6 and 100 times more basic than a pH of 5.
This means that when adjusting the pH of a substance, the amount of chemicals needed to make a certain change in pH can vary greatly depending on the starting pH. In the case of raising the pH of a spa from a 7.1 to a 7.5, you will need to add pH increaser in increments of 1.5 ounces per 100 gallons (42g per 379L) until the pH reaches 7.3, and then decrease to half an ounce per 100 gallons (14g per 379L) to reach a pH of 7.5.
This is because the difference in pH between 7.1 and 7.3 is much larger than the difference between 7.3 and 7.5, so more chemical is needed to make a significant change in pH over that range.
Once you’ve added enough chemicals, test the pH and alkalinity again after letting it circulate through the pump for 5 minutes. Spas are small bodies of water, unlike swimming pools, so it is worth taking your time. Add your products slowly.
Step 4 – Wait
It will take over 10 minutes for the chemicals to mix through the entire system, then you can test again. Do not add any other spa product or try to fill the spa up with fresh water while you are waiting.
Step 5 – Shut Down
When you are satisfied with the levels on the test strips, turn off the pumps and wait for the water to settle. When the turbulence in the water has stopped, you can take a final reading.
Step 6 – Repeat
If you test pH levels outside a suitable range when the pump is off, go back to step one and work through each step again. You may find waiting a little longer, or overnight, will help to stabilize the pH even more.
Using the tub will change the pH levels. Avoid getting in and using the hot tub if the pH is above 7.8 or below 7.2, as this may cause the water to itch or burn the skin.
Frequently Asked Questions
What is pH?
When we test water for acidity or basicity, we measure the pH and potential of hydrogen. The results of a pH test show us the number of free hydrogen and hydroxyl ions present in the water. Hot tub owners should look to keep the water between a pH of 7.2 and 7.8, with a pH of 7.5 being the goal.
The pH scale is logarithmic, not linear. For example, an increase in pH of 1.0 is less acidic by a factor of 10. A pH of 8.0 holds a tenth less hydrogen and 10 times more hydroxyl ions than water with a pH of 7.0.
The assignment of each pH number is a result of an international agreement to describe its effects. A pH of one or lower is ultra-acid, as you would find in a car battery, compared to a strong acidic orange juice with a pH between 3.5-4.0. On the other hand, seawater is a mild base and has a pH between 7.5-8.4, compared to bleach which is above a pH of 12.0.
What is Alkalinity?
Alkalinity helps to buffer the pH of your water, but it is independent of pH. So, when it comes to balancing your pH, you also need to know the amount of alkalinity. Acids come from the chlorine and bromine that you put into the water to sterilize it and, to a lesser extent, the acid released from our skin.
Adding an alkaline solution to your spa helps to combat some of these acids. If you do not neutralize the acids, you are going to have a much harder time trying to balance out the pH.
In Which Order Should I Adjust pH and Alkalinity?
There is an order when adding spa chemicals, and adhering to this order will give you faster and more consistent results. You should try to get your spa’s alkalinity correct before working on the pH. A test showing a pH of zero would mean that there are no such ions present and that the water is extremely acidic.
A pH of 14 is the highest level of basicity, but a spa should not be anywhere near these results. A pH of 7 is neutral – neither an acid nor a base – but a pH of 7.5 is considered to be the most comfortable for occupants of a hot tub.
How Often Should I Check Alkalinity and pH Levels?
Our skin is around a pH of 5.5, but for comfort and to prevent skin irritation, it is better to keep bathing water at around a pH of 7.5. Anything added to the water in your spa is going to change the pH level.
So, after interacting with the water, let the pump run for a further 10 minutes and test the pH, alkalinity, and sanitizer levels. This way, you are ensuring the water stays clean, clear, and safe to use while reducing the number of chemicals you need to use.
Why Turn Off the Spas Air Valves and Blowers?
People want to see the bubbles in a hot tub as they look the part and feel good on the skin. The bubbles enter the water stream while the pump is running and offers a stronger massage than the water jets alone. The problem is that these bubbles aerate the water, increase the churning at the surface, and raise the pH of the water.
Therefore, when testing and adjusting the pH, it is important to turn off the aeration system until you have your spa’s chemicals in the correct range. The chemistry of aeration is a little complex but worth looking at.
These reactions explain what is happening to the pH in the water as air bubbles go up through it:
- Bicarbonate – Bicarbonates (HCO3-) in spa chemicals and fresh water create carbonic acid (H2CO3). Carbonic acid helps reduce pH.
- Aeration – Carbonic Acid (H2CO3) trapped in the water is released as carbon dioxide (CO2) gas when the bubbles flow.
So, the more water (H2O) and carbon dioxide (CO2) that are separated in the carbonic acid, the higher the pH will go.
