How to Lower Alkalinity in a Spa – An Expert‘s Guide

Hey there! I‘m Lillie, a home renovation expert who loves hot tubs. If you‘re struggling to lower the alkalinity in your spa, I‘m here to help. With over 10 years of experience upgrading bathrooms and spas, I‘ve learned the ins and outs of hot tub water chemistry.

In this comprehensive guide, we‘ll cover everything you need to know about reducing high alkalinity levels. I‘ll explain what alkalinity is, the problems it causes, and provide proven methods to lower it based on my expertise. My goal is to give you the knowledge and confidence to balance your spa like a pro!

What Exactly is Alkalinity and Why Does it Matter?

Simply put, alkalinity refers to the amount of bicarbonates, carbonates, and hydroxides dissolved in the water. These compounds act like a "pH buffer", preventing the water‘s acidity from changing rapidly.

The ideal alkalinity range for hot tubs is 80-120 ppm (parts per million). At this level, the water can resist pH changes, keeping your chemicals working properly.

If the alkalinity drops below 80 ppm, the pH becomes unstable and difficult to control. It will swing up and down with every minor change. On the other hand, when alkalinity climbs above 120 ppm, problems start to occur:

• Scale builds up on the hot tub surfaces
• The water becomes cloudy
• Skin and eyes feel irritated
• pH is resistant to adjustment
• Spa equipment gets damaged

Therefore, monitoring and maintaining the proper alkalinity is crucial for water balance and your hot tub‘s health.

How High Alkalinity Harms Your Spa

According to the Pool & Hot Tub Alliance (PHTA), alkalinity levels above 150 ppm can cause the following issues:

• Scale formation on filters, heating elements, and plumbing. This reduces efficiency.
• Cloudy water from scale particles suspended. Makes sanitizing difficult.
• Bathing discomfort and skin/eye irritation. Alkaline water has a soapy feel.
• Shortened life of equipment due to scale buildup and constant operation to combat cloudiness.
• Inability to adjust pH properly due to the alkalinity buffering capacity.

One spa retailer I spoke with said over half their repair calls are related to scale damage caused by high alkalinity. So getting those levels down is really important for your hot tub‘s longevity!

Testing Alkalinity in Your Spa

You need to know the current alkalinity reading before attempting to lower it. Hot tub test strips are handy for quick checks, but liquid test kits give the most accurate measurements.

Here are some tips for getting reliable alkalinity test results:

• Use a fresh water sample each time. Don‘t reuse old samples.
• Carefully follow the test instructions for accurate results.
• Perform tests in natural daylight if color-matching is involved.
• Confirm unusual readings by running a second test.
• Record alkalinity and pH weekly to spot trends.

Once you have a current reading, compare it to the recommended range of 80-120 ppm. If your alkalinity falls within that span, no adjustment is needed right now. But if it‘s above 120 ppm, it‘s time to start lowering it.

How Do I Reduce High Alkalinity Levels in My Hot Tub?

Based on my experience, here are the most effective options for lowering alkalinity in your spa:

1. Use Sodium Bisulfate (pH Decreaser)

Sodium bisulfate, also called "dry acid", is an inexpensive alkalinity lowering chemical. As an acid, it lowers the water‘s pH. But more importantly, it converts excess bicarbonates into carbon dioxide gas that leaves the water, reducing alkalinity.

Dosage Tips:

• Consult your sodium bisulfate package for the ideal dosage based on alkalinity level and spa volume.
• Start with a smaller dose, retest, and add more if needed.
• Pre-mix the chemical with water before slowly pouring it around the edge of the tub.
• Run jets for 30 minutes after adding to circulate.
• Confirm it reached the target range by retesting alkalinity.

Safety Notes:

• Wear gloves and eye protection when handling sodium bisulfate.
• Rinse off any spills on the hot tub surface immediately.
• Remove and rinse off any residue on the cover or pillows.
• Store securely away from children and pets.

2. Drain and Refill Partially

Draining some of the old spa water and replacing it with fresh water is a simple way to lower alkalinity. The new water dilutes the old, reducing alkalinity naturally without adding more chemicals.

Here‘s a quick guide to partial drain and refill:

• Drain 10-25% of total water volume.
• Replace with fresh pre-balanced spa water.
• Clean filters thoroughly before refilling.
• Retest alkalinity after refilling.
• Repeat as needed to reach target range.

Tip: Don‘t drain more than 25% at once or you risk damaging the pumps. I drain and replace 10% per week to maintain lower alkalinity.

3. Use Muriatic or Hydrochloric Acid

For severe cases of off-the-charts high alkalinity, muriatic or hydrochloric acid can lower it quickly. However, I strongly recommend consulting a pool pro before attempting this.

These strong acids must be handled with extreme caution by experienced users only:

• Confirm test kit accuracy at high range.
• Pre-mix acid with water first.
• Add very small amounts gradually, retesting after each dose.
• Rinse spills immediately with fresh water.
• Wear proper eye and skin protection.

Again, muriatic and hydrochloric acids come with safety risks if misused. Seek professional guidance to make sure you add the right amount.

4. Install a Spa Salt Chlorine Generator

While not an instant fix, converting to a salt-based chlorine generator can help maintain lower alkalinity over time. Here‘s how it works:

The generator turns dissolved salt into chlorine for sanitizing the spa water. This process also reduces alkalinity gradually as a byproduct. Run times of 4-6 hours per day will provide the best results.

I installed a salt chlorine generator in my own hot tub 3 years ago and have never needed to lower alkalinity since! While pricier upfront, it paid for itself by reducing chemical costs.

5. Use a Water Softener if Water Source is Very Hard

Finally, if your tap water itself has sky high mineral content, you may need to treat it before it enters your spa. Water softeners remove calcium and magnesium, helping control alkalinity.

Installing a water softener is advisable when:

• Source water is from a private well.
• Local water supply is from a hard water source.
• Alkalinity remains high even after chemical treatment.

Contact your local water company to learn the hardness level of your supply. A reading above 150 ppm may require a water softener.

Maintaining Proper Alkalinity Levels Going Forward

Once you‘ve got your spa‘s alkalinity down to the ideal 80-120 ppm range, here are some tips to prevent it from creeping up again:

• Test and adjust alkalinity weekly. Set a routine test day!
• Change your spa water every 3-4 months to dilute alkalinity.
• Use sodium bisulfate after adding chlorine or shock.
• If on well water, invest in an in-line water softener.
• Inspect equipment and fix any leaks that allow water to evaporate and concentrate.
• Choose spa chemicals formulated not to raise alkalinity.

Staying on top of your water‘s chemistry prevents having to deal with major alkalinity headaches down the road. Consistent testing and preemptive adjustments keep levels right where they should be.

Frequently Asked Questions About Reducing Alkalinity

Still have some questions about lowering alkalinity in your hot tub? Here are answers to some common FAQs:

How much does it cost to lower alkalinity in a spa?

You can lower alkalinity for under $20-30 by using sodium bisulfate or draining/refilling the spa partially. Muriatic acid costs $15-25 per use. More expensive options are $200+ for an in-line water softener or $400+ for a chlorine generator, but these provide long term control.

What happens if I use too much sodium bisulfate or acid?

Using excessive amounts of chemicals like sodium bisulfate or acid can drive the alkalinity too low. This will cause the pH to bounce all over the place, making balancing impossible. It can also damage spa components from the low pH. Add chemicals gradually and retest frequently to prevent overshooting.

Should I drain some water or add chemicals to reduce alkalinity?

For moderate alkalinity increases, draining 10-25% of the water and replacing it with fresh is usually the safest option to avoid adding more chemicals. But for extreme cases, sodium bisulfate or acid may be needed to get the levels down before diluting water. It‘s best to start with the simplest solutions first before trying harsher chemicals.

Why is my spa alkalinity still high after adding sodium bisulfate?

If the alkalinity remains high after adding sodium bisulfate, the dose may have been too low. Double check your math against the dosage chart and volume of your hot tub. Try adding the chemical again based on the current alkalinity reading. Persistently high levels could also indicate a serious underlying issue like damaged plumbing, in need of professional service.

Is muriatic or hydrochloric acid safe to use in a hot tub?

Muriatic and hydrochloric acids are extremely dangerous and corrosive chemicals. While they can be used to lower alkalinity in severe cases, I strongly advise consulting a pool and spa professional before attempting to use either one yourself. Improper dosage of these acids can literally melt your hot tub components and be hazardous to your health.

The Bottom Line

I hope this guide gives you the confidence to get your spa‘s alkalinity under control. Test it weekly and react quickly if it starts to creep above 120 ppm. Sodium bisulfate, drain and refill, salt chlorine generators, and water softeners are your best tools for lowering high alkalinity.

With routine testing and these proactive tweaks, you can avoid major water chemistry headaches. Please reach out if you need any help getting those alkalinity levels perfect! I‘m happy to offer free advice to fellow spa enthusiasts. Enjoy that hot tub!