How to Raise pH in a Pool Safely

To raise pH in a pool, test total alkalinity first, then choose the right fix: soda ash (sodium carbonate) if alkalinity is normal, baking soda if alkalinity is also low, or aeration if alkalinity is already high. Add products in small doses with the pump running and retest after a few hours. Most pool owners aim for pH 7.4–7.6, and CDC recommends keeping it between 7.0 and 7.8.

Why low pH is a problem

pH measures how acidic or basic the water is. When it falls below about 7.2, water becomes aggressive:

• Eyes and skin sting, and swimsuits fade faster.
• Metal corrodes: ladders, rails, heat exchangers and pump seals wear out early, and dissolved copper can stain surfaces.
• Plaster and grout etch, feeling rough underfoot.
• Vinyl liners can wrinkle and age faster.

Low pH also makes chlorine readings harder to interpret, and it tends to come with low alkalinity, which lets pH swing wildly.

Why pool pH drops

• Trichlor tablets. The most common pool tablets are acidic and pull pH (and alkalinity) down steadily.
• Too much acid added when lowering pH or alkalinity.
• Rain, which is slightly acidic and dilutes your buffer.
• Low total alkalinity, which leaves nothing to resist small changes.
• Heavy use, since swimmer waste and debris consume chlorine and produce acidic by-products.
• Non-chlorine shock (MPS), which is mildly acidic.

Choose the right fix

Our guide to raising total alkalinity covers the baking soda route in detail. If you use borax, add it slowly: it also adds borates, which buffer pH and make later acid doses a little larger.

How to raise pH with soda ash

1. Test pH and total alkalinity with a reliable kit.
2. Work out the dose. Enter your volume, pH and alkalinity into our pool chemical dosage calculator, or follow the product label. The amount depends heavily on alkalinity, so a fixed rule of thumb can be well off.
3. Run the pump on its normal filter setting.
4. Add about three-quarters of the dose. Broadcast it over the deep end or pre-dissolve it in a bucket of pool water, as the label directs. Large doses added in one spot can cloud the water briefly.
5. Wait a few hours, then retest pH.
6. Top up in small steps until pH reaches 7.4–7.6.

How to raise pH with aeration

Aeration drives dissolved carbon dioxide out of the water, which raises pH but leaves alkalinity unchanged. It’s slower than soda ash, but ideal when alkalinity is already high:

• Point return jets upward so they break the surface.
• Run waterfalls, fountains, deck jets or a spa spillover.
• Use an air blower or bubbler if you have one.
• Brush the pool and keep the pump running longer.

Expect pH to climb over a day or two. Retest each morning and stop aerating once pH reaches 7.4–7.6, or it will keep climbing. This same effect is why pH creeps up in pools with lots of water features.

Why pH keeps falling

If you raise pH and it drops again within days:

• Check your tablets. Trichlor lowers pH and adds stabilizer every day it dissolves. Our cyanuric acid guide explains why long-term tablet use can push stabilizer too high.
• Check alkalinity. Below about 80 ppm, pH has almost no buffer. Fix alkalinity first.
• Check your acid dosing. If you’ve been lowering pH, you may simply have overshot.

Don’t overshoot

Above about 7.8, chlorine loses much of its strength, scale forms on tiles and heaters, and water can turn dull. If you go too far, our guide to lowering pH shows how to bring it back down gently. Small doses and patient retesting beat one big correction every time.

Quick checklist

• Test pH and alkalinity before adding anything.
• Fix alkalinity first if it’s low.
• Use soda ash for normal alkalinity, aeration for high alkalinity.
• Add three-quarters of the dose, then retest.
• Keep chemicals separate and follow each label.

Frequently asked questions

Can I use baking soda to raise pH?

Yes, if alkalinity is also low. Baking soda raises alkalinity a lot and pH only a little. If alkalinity is already in range, soda ash is the better choice.

How long after adding soda ash can I swim?

Follow the product label. Many labels allow swimming once the product has fully circulated and pH is back in range, but check yours.

Why did my pool turn cloudy after adding soda ash?

A big dose raises pH sharply in one area, and calcium in the water can briefly come out as fine particles. Keep the pump running; the filter usually clears it within a day. Next time, split the dose.