How to Raise pH in Hot Tub

How To Raise pH in Hot Tub

Like any other major purchase, if you have decided to invest in a hot tub you will want to know how to properly maintain it in order to extend its lifespan. You’ll need to keep the water balanced to gain benefit from owning your own hot tub so your and friends can use it safely.

There is a short list of chemicals that you will need to keep on hand to keep the water maintained and the pH and alkalinity levels balanced.


PH test strip kit for hot tubs

An inexpensive test strip kit to check pH levels in your hot tub water

The chemicals used to balance pH and alkalinity are inexpensive but are extremely important. Water pH is a measurement of the acidity of your water.

As a general rule, your hot tub pH should be between 7.2 and 7.6 which is classed as a neutral range. Levels lower than 7 are too acidic and levels higher than 7 are alkaline (not acidic enough).


Just to give you an idea why this is, our skin acidity is 7.35 to 7.45, so this lies in the middle of the suggested water acidity range – that way we are more comfortable in our spa and at this range bugs are kept under control more easily.

If your pH fluctuates outside that safe zone, the water becomes unsafe and can cause corrosion, mineral scaling, or you can face unhealthy bacterial growth.

Alkalinity is a measure of the water’s ability to buffer the pH to neutralize the acid.

It may seem complicated at first, but with a little practice it becomes routine.

It helps keep pH levels stable so when your water dips out of range, you can simply adjust your TA (Total Alkalinity) without having to completely redo your hot tub chemistry.

Alkalinity should be between 125ppm and 150ppm and be adjusted first since it keeps your pH in check, so when it slips levels, your pH will as well.

Failure to maintain alkalinity may result in corrosion, phosphate imbalance which can lead to algae growth and green water, mineral build-up, and cloudy water.

On top of these effects, there’s every chance you will be developing bacteria-rich water by allowing bacteria from either side of neutral to breed to excess.

What causes low pH in hot tub?

Testing kits for pH levels are available at pool supply stores. You dip a strip into the water and read the pH by matching the color it turns to a scale printed on the bottle. The ideal level should be in the neutral range.

The one in the picture shown runs at just over the $10 mark directly from Amazon, so there’s no great cost involved with these tests.


You will also need some test strips to take a sample of your water – again, inexpensive.


An alternative to the test strips is to use a digital meter costing almost double but this one does not need the strips, so will soon pay for itself.


Anything below 7.2 ppm is considered to be too acidic.

Elevated levels of acid cause sanitizing chemicals to become ineffective allowing harmful contaminants to come in contact with bathers, which can lead to rashes and eczema.

It can also irritate swimmer’s skin and eyes. Too much acid takes its toll on your tub’s components causing them to corrode.


So, what causes low pH in hot tub spas making the water excessively acidic?


In a word, if you’ve set the chemical levels right to start with, it’s YOU – and anyone who joins you in the hot tub.

It is well known we all sweat in hot tubs, and it is these bodily fluids, along with flaky skin, anything that is or was living, rots down and causes acidity. So the more people you have in there and for a longer time without water changes, then your water will grow more and more acidic as time passes.


On top of that pH that’s too low can be caused by the type of water you use.

Soft water will have a completely different pH than hard water. Thus, when you add water, it will alter your level accordingly.

Different chemicals you use will also cause fluctuations since they have different pH ranges too. When the time comes to add more chemicals, the levels will change depending on the amount used and the pH level of that specific chemical.


How to raise pH in hot tub

Low levels can cause skin irritation and degrade the spa’s heater and other components. The pH levels in your hot tub can be increased by using magnesium oxide which has the ability to neutralize carbon dioxide.

The first step is to adjust the alkalinity using either of the test methods above.

The next step you take in how to raise pH in hot tub spas is you gradually add an increaser like SpaGuard pH Increaser to get the right reading.

Then allow the tub to run for 30 minutes to evenly circulate the chemicals.

Last, turn off the jets and conduct a retest to ensure the alkalinity is still at proper levels.


What causes high pH in hot tub?

A high pH level is a level above 7.6 ppm. This means your water is too basic, too alkaline, and when your water pH is too high, it can begin to form scales.

Scales are a white and chalky residue that’s rough to the touch and can be found on the tub’s surfaces.

These scales can block water circulation by becoming lodged in pipes and blocking their flow. As they build, scales will cause early equipment failure.

These scales are formed by the Alkaline effect forming lime which eventually will become like chalk in that it will block your pump and piping if left for too long without balancing the water.


On top of this, you may notice a greeny tinge developing in your water which, if left too longe, will eventually form algae.


So, what causes high pH in hot tub and spas? How do you fix it?

You will need to regularly use a pH reducer and we recommend Leisure Time Spa Reducer.

Reducers usually consist of dry acid crystals such as sodium bisulfate but liquid forms are also readily available.

The pH reducer needs to be added gradually over a period of time depending on the manufacturer’s recommendation. You add it gradually, allow it to circulate, and then retest the pH level. If it is still too high, you repeat the process until it gets in range. Adding too much reducer too quickly can result in making the water too acidic that you will have to get to come back down.

The most common reason for an elevated pH level is a very high alkalinity level. Since alkalinity acts as a buffer to help keep pH in range, when it raises, so will your pH level because it will not be able to keep it under control.

Hot tubs run at a higher temperature and produce bubbles which cause a buildup of carbon dioxide. The carbon dioxide is also notorious for raising both pH and alkalinity. As has been stated, this carbon dioxide is also a result of living matter decomposing.


How much muriatic acid to lower pH in hot tub?

Muriatic acid (also called hydrochloric acid) is another chemical commonly used to lower a spa pH level that is too high. The amount you use will depend on the capacity of your hot tub and how high the pH actually is.

How much muriatic acid to lower pH in hot tub spas? Here is a general amounts guide:

• 400 gal. spa: 
o 7.6-7.8: .5 fl oz.
o 7.8-8: .6 fl oz.
o 8-8.4: 1 fl oz.
o Above 8.4: 1.3 fl oz.

• 750 gal. spa:
o 7.6-7.8: .9 fl oz.
o 7.8-8: 1.2 fl oz.
o 8-8.4: 1.9 fl oz.
o Above 8.4: 2.4 fl oz

• 1500 gal. spa:
o 7.6-7.8: 1.9 fl oz.
o 7.8-8: 2.4 fl oz.
o 8-8.4: 3.6 fl oz.
o Above 8.4: 4.8 fl oz


How to lower pH in hot tub home remedy?

Many people have issues where the spa chemicals can irritate their skin or cause health problems. Others may just want a more natural alternative.

That leaves many questioning how to lower pH in hot tub home remedy?

Here are a few alternative methods to lower pH levels without harsh substances.

• Lemon juice or vinegar both contain acids that can bring pH levels down. You will have to use plenty of it because vinegar only contains about 5 percent acid.
Using peat moss is generally thought of as the most effective natural method of dropping pH. Peat moss can be placed in a mesh bag and placed somewhere the water will flow through it.
• Driftwood acts as a natural filter. It will need to be soaked for a few days prior otherwise it will discolor water.
Use distilled water
• Install a carbon dioxide system to monitor and adjust pH levels automatically 

Another alternative to using chemicals is to use baking soda to reduce the acidity of your water – check out our post on How Much Baking Soda to Raise Alkalinity in Hot Tub


Again – if you are not into chemicals, then I suggest you take a look at our post Running Hot Tub Without Chemicals


Keeping your hot tub water in at a neutral pH level is important both for the longevity of your spa, as well as for the people who use it.

Alkalinity and pH go hand-in-hand and work together to keep your water safe. Without regular chemical maintenance and testing, you will experience issues like bacterial growth, algae, scaling, eye and skin irritation, and corrosion.

So make sure you know how to raise or lower pH in your hot tub for your own benefit and your hot tub’s.

On the other hand, if you are like me, lazee, and want an easier option, how about the  pHin Wi-Fi-Enabled Smart Water Care Monitor for Hot Tubs and Pools.

Once set up, just drop it in your pool water and it will let you know as any problems arise and literally tells you, directly to your phone, what needs doing to correct the problems.

Not cheap, but well worth the loss of aggravation.

There are even videos showing how to set it up and how it works here.



We use one ourselves and can highly recommend them.

With 135 positive customer reviews so far. – It’s a Godsend to us!  


Why not check out some of our other informative posts:

8 thoughts on “How to Raise pH in Hot Tub

  1. So we’ve not had our hot tub long and I changed it a week ago and added some chlorine to keep the water sanitised as I knew we wouldn’t use it for a week. I’ve tested it a week later and the Ph is 6.6 which is too acidic and I’m now panicking that I may have damaged it. I’m currently working on correcting this but does anyone know how long left this way may start to cause corrosion? It’s been a week and when we went to use it tonight the thermostat say 35 degrees but I don’t think it was anywhere near that temp.

    1. Hi Gareth
      There’s no need to panic about too much corrosion at that level. I’d reckon on around twelve months before you do any serious damage. The chlorine itself will naturally evaporate, but if you want to add around an ounce of baking soda and check it after thirty minutes with the pump running, you’ll find the acidity levels lower. Just add another ounce and check it again until you get it right and all will be well.

      You obviously have overdosed on the chlorine!

      Thermostats are not always accurate, so simply adjust it to suit yourself.

  2. I have a similar ph problem in that it is static at 7.0 and I was heartened to read above that it might take around 12 months to do damage via corrosion

    That said I have bought Magnesium Oxide to aise my ph BUT how do I apply this please ? I could not dissolve it using Hot tub water or even boiling water so is it a case of just putting a measured amount in


    1. Hi John, This lack of dissolving could well be down to the product you have bought. There are three types available, two for pools that take much longer to dissolve, and an anhydrous version suitable for hot tubs. The crystals need to be left in the water as they will dissolve over time, but if you empty out your hot tub, they will be gone and serve no further purpose.

      The simplest way is to use the ‘old-fashioned’ baking soda. To raise your water up from 7.0 to around 7.5 you need around 2.5lbs/1000 gallons. It dissolves almost instantly providing your pumps are on and there is no residue to worry about.

    2. Should also have added that with a reading of 7.0 pH, your water is neutral, meaning corrosion will be non-existant. It will not effect your piping, heater or pumps.

      The reason we have it a little more alkaline (around 7.5 or7.6) is because that matches our own pH readings, meaning it is most comfortable for us.

      One good point of a 7.0 reading is there will be virtually no bacteria present in your water, but it may be a little uncomfortable to be in.

  3. Thanks very much Lisa

    I am still battling away having a TA off the scale of my tester – and so added ph minus to bring that down with a view to then adding BoS or similar

    I took 2 days and several tests to get TA in desired zone with pH at 6.3 using Apera tester

    Then I added Borax as I had read somewhere that that would raise pH but leave TA alone but it did nothing to the pH and that was 100g over 4 applications

    I then moved on to Bicarb with the same effect and then finally added Magnesium Oxide in three doses yesterday. The pH finally complied and moved to 7.0 so I was really pleased BUT when tested the TA had zoomed back up to where it started

    I am considering drain and refill rather than chasing the results up and down. We have had the Tub for 3 months so it is probably “time”

    Do you agree ? Thanks JT

    1. Hi John, yes I’d fully agree with your prognosis. Chasing the chemical balance is really a never-ending problem creator, a non-starter really, as the simplest option is to start again from scratch, as the more chemicals you use means more chemicals need to be introduced to try to balance it right.

      The best bet is to keep everything simple and change the water more often when the balance is starting to go off, as over time there’s bound to be more fluctuation with use – it’s totally natural.

      Just make sure you shock it weekly if it’s used a lot and I’d make a point of adding something to wash out your plumbing like The Natural Hot Tub Company Penetrating Spa Cleanser which I have found is very effective as it’s something we’d do at the start of the season just to make sure the piping is clear of any residues.

      Trouble is, it has to be run for 8 hours in a full tub, drained and then refilled which means you could be without your hot tub for at least two days.

      That should solve your problems and give you a more pleasant time with your hot tub.


  4. Hi Lisa …
    … and thanks once again for the reply. I am going to change the water in the upcoming week
    It has “done” 90 days now and despite there being only 2 of us the Change Water reminder has come up … but that would happen even if the Tub was not being used

    I will then have a clean start and add the Chemicals sparingly and in tiny amounts so as not to take big bets.

    Thanks again JT

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