Borax is one of the cheapest ways to make pool water feel softer and hold its pH steady. It is also one of the easiest to get wrong, because most dosing advice online is written in US gallons for US products.
This guide covers what borax does in a pool, the levels to aim for, and how to work out your own dose in litres.
What Does Borax Do for a Pool?
Borax raises pH and, once converted, leaves borate in the water. Borate is a pH buffer. It slows the natural pH rise that comes from aeration, water features and salt chlorinators.
Pool owners who add borax usually report three things.
- pH stops drifting upward every few days, so you use less acid
- The water feels softer and looks brighter
- Algae struggles to establish, so chlorine lasts longer
Borax on its own is a base. It pushes pH up. Acid is what converts it into borate. That is why the acid is part of the job and not an afterthought.
Borax in Pool Water: The Level to Aim For
The accepted target range is 30 to 50 ppm borate. Most owners settle around 50 ppm.
Going above 50 ppm adds cost without adding benefit. There is no reason to chase a higher number.
Why Borax in a Pool Needs a Real Test Reading
Borate does not show up on a standard test strip. You need a borate-specific strip or a lab test.
Dosing blind is the most common mistake. If you do not know the current level, you cannot know the gap you are filling.
How Much Borax to Add to a Pool
Published borax dosing figures disagree with each other, sometimes by a factor of more than one and a half. Some charts are written for borax decahydrate, others for boric acid or sodium tetraborate pentahydrate. Those three products need very different quantities for the same result.
We are not going to print a single gram figure here, because the wrong one can cost you a few thousand rand in product or leave the pool nowhere near target.
Do this instead.
- Work out your pool volume in litres first
- Test the current borate level with a borate strip
- Read the dose table on the product you actually bought, matched to litres
- Split the dose in half and add it over two sessions, testing in between
Our pool volume guide walks through the measurement if you do not have it.
Adding Borax to a Pool Safely
Run the pump. Broadcast the borax slowly across the surface. Let it circulate for an hour before testing.
Expect pH to climb. Bring it back down with acid in small steps. Do not dump acid and borax in together.
Borax for Pools in Cape Town: What Is Different Here
A lot of Cape Town pools top up from a wellpoint or borehole. That water often carries iron and higher hardness than municipal supply.
Borax raises pH, and a pH spike in water that already holds metals can drop those metals out as staining. If your fill water is from a borehole, test for metals before you start.
Summer wind is the other local factor. Wind-driven aeration pushes pH up all season, which is exactly the problem borate buffering solves.
Boric Acid or Borax for Swimming Pools?
Borax raises pH as it works, so you add acid afterwards. Boric acid is closer to pH neutral, so there is less correcting to do.
Boric acid usually costs more per kilogram. Borax is easier to find in South Africa and is often the cheaper route if you are comfortable managing pH.
| Product | Effect on pH | Availability in SA |
|---|---|---|
| Borax (sodium tetraborate decahydrate) | Raises pH, needs acid after | Widely available |
| Boric acid | Close to neutral | Specialist pool suppliers |
| Sodium tetraborate pentahydrate | Raises pH | Specialist pool suppliers |
When Borax in a Swimming Pool Will Not Fix the Problem
Borate buffers pH. It does not sanitise, it does not clear algae on its own, and it will not rescue a pool with a failing filter.
If the water keeps going green or cloudy after dosing, the issue is circulation or filtration. Check run time and filter condition before buying more chemicals.
Does Borax in a Swimming Pool Raise pH?
Yes. Borax is a base, so it pushes pH up as it dissolves. You bring pH back to 7.4 with acid afterwards. Boric acid does the same job with far less pH movement.
What Does Borax Do for a Pool Long Term?
Borate stays in the water. It does not burn off like chlorine. A single correct dose keeps buffering pH for months, which is why adding borax to pool water is popular with owners tired of weekly acid dosing.
Get Your Pool Borate and Water Balance Tested in Cape Town
Dosing works when the starting reading is right. A cheap strip that is six months old will send you in the wrong direction.
Our team tests water on site across Cape Town and the Winelands. We balance the pool properly and tell you what it actually needs, not what a generic chart says. Request a free quote or browse our pool maintenance services.
