Figuring out exactly how much borax to add to pool to raise ph can feel a bit like a high school chemistry project you never actually signed up for. If you've walked out to your backyard only to find your eyes stinging or your skin feeling like sandpaper after a quick dip, your pH is likely bottoming out. While most pool shops will try to sell you a fancy container of "pH Increaser," many seasoned pool owners just head to the laundry aisle of the local grocery store for a box of 20 Mule Team Borax. It's the same basic chemistry, just way cheaper and often more effective.
The short answer is that you typically need about 20 ounces of Borax to raise the pH of 10,000 gallons of water by roughly 0.5 units. But, as anyone who has ever accidentally turned their pool into a cloud of white dust knows, there's a bit more nuance to it than just dumping a box over the side.
Why Borax is a Secret Weapon for Pool Owners
Most people assume they need sodium carbonate (soda ash) to fix a low pH. Soda ash definitely works, but it has a side effect: it raises your total alkalinity (TA) quite a bit. If your alkalinity is already where it needs to be, but your pH is sitting at a dismal 7.0, using soda ash is going to throw your TA out of whack.
This is where Borax shines. It raises the pH significantly while having a much smaller impact on your total alkalinity. Plus, it adds borates to the water. Borates are great because they act as a secondary pH buffer, make the water feel "silky" on your skin, and even help inhibit algae growth. It's basically a triple threat for pool maintenance.
Calculating Your Dosage
Before you start pouring, you have to know two things: your current pH level and the total volume of your pool. If you don't know how many gallons your pool holds, you're just guessing, and guessing usually leads to a seesaw of chemical corrections that last all weekend.
The General Rule of Thumb
If you're aiming for a standard increase, here's a quick breakdown of how much borax to add to pool to raise ph based on common pool sizes:
- 10,000 Gallons: Add 20 ounces (by weight) to raise pH by about 0.5.
- 15,000 Gallons: Add 30 ounces to raise pH by about 0.5.
- 20,000 Gallons: Add 40 ounces (one full 2.5 lb box) to raise pH by about 0.5.
Keep in mind that these are estimates. If your pH is extremely low—say, under 7.0—you might need to do this in stages. It's always smarter to add a little less than you think you need, wait for it to circulate, and then test again. You can always add more, but taking it out is a much bigger headache.
Step-by-Step: How to Add Borax Properly
You don't want to just chuck a pile of powder into the deep end and hope for the best. If Borax isn't distributed properly, it can sit on the floor of the pool and potentially cause issues with the liner or just take forever to dissolve.
1. Test Your Water First
Don't rely on "the water looks a bit off." Get a high-quality drop test kit. Test strips are okay for a quick glance, but when you're adjusting pH, you want accuracy. Ideally, your pH should be between 7.4 and 7.6. If you're sitting at 7.2, you might not even need to do anything. If you're at 7.0 or lower, it's time to act.
2. Measure the Borax
Use a kitchen scale if you have one, or a measuring cup. Since Borax is a powder, 20 ounces by weight is roughly 2.5 to 3 cups by volume. Don't stress too much about being precise to the gram, but try to stay close to the recommended ratio.
3. Pre-dissolve (Optional but Recommended)
If you have a vinyl liner pool, it's a good idea to dissolve the Borax in a 5-gallon bucket of pool water first. Give it a good stir with a wooden stick or a plastic paddle. If you have a plaster or gunite pool, you can usually get away with broadcasting it directly into the water, but pre-dissolving ensures you don't get any clumps.
4. Pour Near the Return Jets
With the pump running on its normal filter setting, pour the Borax (or the bucket mixture) slowly into the pool. The best spot is right in front of the return jets—the holes where the water pumps back into the pool. This helps the chemicals circulate quickly and evenly throughout the entire body of water.
5. Let it Circulate
Give the pool at least 4 to 6 hours to fully circulate the new chemistry. If you have a massive pool, you might want to wait a full 24 hours before doing your follow-up test.
Why Did My pH Drop Anyway?
It's frustrating when you feel like you're constantly fighting the water chemistry. Understanding why the pH dropped in the first place can help you prevent it next time.
- Heavy Rain: Rainwater is naturally acidic. After a big summer thunderstorm, it's very common to see your pH levels dip.
- Heavy Bather Load: If you had a big pool party with ten kids splashing around, the sweat, oils, and "other things" people leave behind can drive the pH down.
- Chlorine Choice: If you use "pucks" (trichlor tabs) in a chlorinator, those things are incredibly acidic. They do a great job of sanitizing, but they will slowly eat away at your pH and alkalinity over time.
- Organic Debris: Leaves and pine needles decaying at the bottom of the pool release tannins and acids that lower the pH.
A Note on Total Alkalinity
I mentioned this earlier, but it's worth repeating: pH and Alkalinity are best friends. If your total alkalinity is too low (below 80 ppm), your pH will be "unstable." It will bounce around like a ping-pong ball no matter how much Borax you add.
Before you obsess over how much borax to add to pool to raise ph, check that alkalinity reading. If the alkalinity is in the 80-120 ppm range, the Borax will work like a charm. If the alkalinity is super low, you should probably fix that first with some baking soda, and you might find the pH stabilizes on its own.
Is Borax Safe for Swimmers?
This is a common question. People get nervous about putting "laundry detergent" in their pool. First off, Borax isn't detergent; it's a natural mineral (sodium tetraborate). Once it's diluted in thousands of gallons of water, it's perfectly safe.
In fact, many high-end pool systems specifically use borates to maintain water clarity. You could theoretically jump in right after adding it, but it's usually best to wait about 30 minutes to an hour just to make sure it's fully mixed and you don't swim through a "cloud" of concentrated product.
Final Thoughts on Using Borax
Keeping a few boxes of Borax in the garage is one of the best "hacks" for pool owners. It's cheap, it's effective, and it doesn't cause the massive alkalinity spikes that other products do.
Just remember the golden rule: 20 ounces per 10,000 gallons for a 0.5 pH bump. Start slow, test often, and you'll have that water looking crystal clear and feeling comfortable in no time. Pool maintenance doesn't have to be a wallet-draining mystery—sometimes the best solution is sitting right there in the cleaning aisle.