Testing & Chemistry
Pool pH Too Low
The reading that costs you equipment rather than a weekend, and the one correction where the right product depends entirely on a second number.
We have not handled these products and we do not pretend to have. Here is what we did instead. Links to Amazon earn us a commission at no extra cost to you, and commission never decides a pick — disclosure.
| # | Product | Best for | The spec it turns on | Price |
|---|---|---|---|---|
| 1 |  Pool Mate Premium pH Up, 10 lbTop pickThe other chemical. Soda ash is for pH, not for alkalinity, and buying it by mistake is the most common way to end up correcting twice. | Low pH when alkalinity is already fine | Listing states 100% sodium carbonate (soda ash) and a 7.2-7.6 pH target | |
| 2 |  Leslie's Soda Ash pH Up, 100% Sodium Carbonate, 10 lbThe only soda ash here that publishes both a dose and a maximum single addition, which is the number that keeps you from overshooting pH. | Soda ash with a published dose and a cap | Listing states 100% sodium carbonate, 1 lb per 10,000 gallons below pH 7.2, and no more than 4 lb per 10,000 gallons at once | |
| 3 |  Doheny's pH Plus Granular Soda AshSoda ash in a pouch rather than a tub, which is the right size for a pH correction that should be small and checked. | A small pouch for one correction | Listing states pro-grade granular soda ash (sodium carbonate), sold in 5 and 10 lb pouches or a 25 lb bucket | |
| 4 |  Pool Mate Premium Alkalinity Increaser, 10 lb100% sodium bicarbonate and it says so, which is the only claim that lets you compute the dose yourself. | Raising total alkalinity | Listing states 100% sodium bicarbonate | |
| 5 |  In The Swim pH Increaser for Pools, 25 lbThe bulk tub, and the only listing here that admits plainly that soda ash raises alkalinity as well as pH. | A season of corrections on an acidic pool | Listing states sodium carbonate, raises both pH and total alkalinity, target pH 7.2-7.6 | |
| 6 |  20 Mule Team 20 Mule Team Borax Detergent Booster, 65 ozThe unlabeled route. Borax does raise pH with less effect on alkalinity than soda ash, and nothing on this box says a word about pools - which is the caveat, not a secret. | Pool owners who already know why they want borate | Laundry product: the listing states only that it is a multipurpose household cleaner that makes detergent work better, and makes no pool claim at all | |
| 7 |  Taylor Technologies K-1004 DPD 6-in-1 Pool Test KitIncludes an acid demand test, which is the only honest way to know how much pH reducer your pool needs. | The acid demand test | DPD kit including acid and base demand titrations |
Low pH is the expensive direction
High pH clouds water and blunts chlorine, and it is annoying. Low pH dissolves things you paid for. Acidic water etches plaster, washes grout out from between tile, corrodes ladders, rails and the copper inside a heater, and degrades the rubber and vinyl it touches on the way.
None of that reverses. A plaster surface that has been held acidic for a season comes back rough and stays rough, and a heater core that has been leached does not un-leach. This is why pH gets corrected downward in a hurry and upward with a shrug, when the second one is the one with a repair bill attached.
It is also uncomfortable. In The Swim's own pH Increaser listing puts it plainly: above 8 the water risks skin rashes, below 7 it stings eyes. The sting people blame on chlorine is usually pH.
Check alkalinity before you buy anything
This is the whole decision, and it takes one test. Total alkalinity is the buffer that holds pH steady, so a pool with low pH and low alkalinity has a different problem from a pool with low pH and normal alkalinity - and a different product.
| pH | Total alkalinity | What to use | Why |
|---|---|---|---|
| Low | Below 80 ppm | Sodium bicarbonate | Fixes alkalinity, and pH drifts up with it - often far enough |
| Low | 80-120 ppm | Soda ash (sodium carbonate) | Moves pH hard with a smaller effect on alkalinity |
| Low | Above 120 ppm | Aeration, then reassess | Aeration raises pH without adding alkalinity to a pool that has too much |
| Fine | Below 80 ppm | Sodium bicarbonate | An alkalinity job, not a pH one |
The most common mistake on this page is buying pH Up when the real reading out of range is alkalinity. Soda ash moves pH quickly, the pool reads 7.5 that evening, and a week later it is back at 6.9 because nothing is holding it there. How to raise alkalinity is the page for that case, with the bicarbonate dose worked out in full.
Why there is no pH dose chart on this site
Every dose table here is computed from chemistry - chlorine, stabilizer, alkalinity, calcium. There is no pH table, in either direction, and the reason is that pH does not have one.
How far a given dose moves pH depends on the water's buffering capacity, which is its total alkalinity. The same pound of soda ash that lifts a weakly buffered pool by half a point barely registers in a pool at 140 ppm. A chart that ignored alkalinity would be wrong for most pools that read it.
That is exactly what a base demand test measures. Taylor's K-1004 includes acid and base demand titrations: you titrate a sample of your own water and read off what your pool needs, rather than dosing from an average pool that does not exist.
Soda ash, bicarbonate and borax
Three compounds get used for this, and they are not interchangeable. Two are labeled for pools and one is not.
| Soda ash | Sodium bicarbonate | Borax | |
|---|---|---|---|
| Sold as | pH Up, pH Increaser, soda ash | Alkalinity Increaser, Alkalinity Up | Laundry booster |
| Raises pH | Sharply | Slightly | Moderately |
| Raises alkalinity | Yes - In The Swim states it plainly | Yes, this is its job | Far less than soda ash |
| Published pool dose | 1 lb per 10,000 gal (Leslie's only) | 1.4 lb per 10,000 gal per 10 ppm | None - not a pool product |
| Published pool target | 7.2-7.6 | 80-120 ppm alkalinity | None |
| Testable afterwards | Yes, any kit | Yes, any kit | Not on any kit featured here |
The honest position on borax is that it works and its box says nothing about pools. 20 Mule Team's listing states that it softens hard water and boosts detergent - there is no pool dose, no target range and no pool claim anywhere on it. Pool owners use it because sodium tetraborate lifts pH while moving alkalinity much less than soda ash does.
We are not going to print a dose the maker does not publish. If you use borax, you are working from pool-forum arithmetic rather than a label, and you are adding something that none of the test kits on this site measures. That is a reasonable trade for an owner who knows why they want borate in the water, and a poor one for anyone who just wants pH fixed.
Aeration: the free option, for one specific case
If pH is low and alkalinity is high, adding anything makes the second problem worse. Aeration is the answer, and it costs nothing.
Agitating the surface drives dissolved carbon dioxide out of the water, and pH rises as it goes - without adding a gram of alkalinity. Point the returns upward to break the surface, run a waterfall or a fountain, or run the spa jets. It is slow, it is free, and it is the same mechanism used in reverse on how to lower alkalinity.
On a pool with alkalinity in range, aeration still works but soda ash is faster. On a pool with low alkalinity, skip it - you need bicarbonate, and it will bring pH with it.
Why your pH keeps falling
A pool that needs pH Up once is having a season. A pool that needs it monthly has a source, and correcting the reading without naming the source is a subscription.
- Trichlor tablets. Strongly acidic, and the most common cause by a wide margin. A tablet-fed pool drifts down on both pH and alkalinity all season - the running cost is set out on best chlorine tablets.
- Acid you added. Chasing high alkalinity with acid pulls pH down with it, which is the whole difficulty of that correction.
- Rain. Rainwater is mildly acidic and dilutes the buffer at the same time, so a wet fortnight moves both readings down.
- Dichlor shock. Like trichlor, it is acidic and it adds cyanuric acid on top - see cyanuric acid.
- Low alkalinity itself. With no buffer, pH does not need a reason to move. Fix alkalinity and the pH stops wandering.
How to add it
- Test pH and total alkalinity together, and write both down. The second reading picks the product.
- Work out your pool's volume if you do not know it - every published dose is per 10,000 gallons. The shape formulas are on how to balance pool water.
- If alkalinity is below 80 ppm, use sodium bicarbonate and stop here. Retest in a day; pH has often corrected itself.
- If alkalinity is in range, start with 1 lb of soda ash per 10,000 gallons, per Leslie's label, and never exceed 4 lb per 10,000 gallons in one addition.
- Broadcast it over the deep end with the pump running. Soda ash dissolves quickly but can cloud the water briefly where it lands.
- Wait a full turnover, then retest. An hour is not long enough, and the second dose added on an early reading is the one that overshoots.
The picks
Top pick - Low pH when alkalinity is already fine
Pool Mate Premium pH Up, 10 lb
The other chemical. Soda ash is for pH, not for alkalinity, and buying it by mistake is the most common way to end up correcting twice.
The published figure
Listing states 100% sodium carbonate (soda ash) and a 7.2-7.6 pH target
Pool Mate states 100% sodium carbonate and that it raises pH rapidly, with a 7.2 to 7.6 target. Sodium carbonate is a different compound from the sodium bicarbonate in alkalinity increaser, and it behaves differently in the water.
Reach for it when pH is low and total alkalinity has already tested in range. If both are low, bicarbonate first: raising alkalinity nudges pH up on its own, and you may need no soda ash at all.
It is stated to prevent erosion and etching of pool surfaces, which is what low pH does to plaster over time.
What it does well
- States 100% sodium carbonate
- Raises pH quickly when alkalinity is already in range
- Sold by Amazon, so delivery is predictable
What it costs you
- Wrong product if what you actually need is alkalinity
- Raises pH sharply, so it is easy to overshoot
- Publishes no maximum single dose, unlike the Leslie's label
Skip it if your total alkalinity is below 80 ppm. Fix that first with bicarbonate and retest pH afterwards.
Pick 2 - Soda ash with a published dose and a cap
Leslie's Soda Ash pH Up, 100% Sodium Carbonate, 10 lb
The only soda ash here that publishes both a dose and a maximum single addition, which is the number that keeps you from overshooting pH.
The published figure
Listing states 100% sodium carbonate, 1 lb per 10,000 gallons below pH 7.2, and no more than 4 lb per 10,000 gallons at once
Leslie's states 1 lb per 10,000 gallons when pH is below 7.2, and explicitly caps a single addition at 4 lb per 10,000 gallons. A cap is unusual on a balancer label and it is the more useful of the two figures.
The listing states it raises pH and total alkalinity together, and gives its ranges as 7.4 to 7.6 pH and 80 to 140 ppm alkalinity. That dual effect is exactly why soda ash is the wrong tool when only alkalinity is low - it drags pH up with it.
It is stated to dissolve rapidly, which is worth having: a balancer still sitting on the floor has not moved your reading yet.
What it does well
- States 100% sodium carbonate
- Publishes a dose and a maximum single addition
- Stated to dissolve rapidly
What it costs you
- Raises alkalinity as well as pH, so it is easy to overshoot both
- Third-party seller, so shipping time varies
- Its stated 140 ppm alkalinity ceiling is higher than most labels give
Skip it if your pH is fine and only alkalinity is low. That is a bicarbonate job.
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Pick 3 - A small pouch for one correction
Doheny's pH Plus Granular Soda Ash
Soda ash in a pouch rather than a tub, which is the right size for a pH correction that should be small and checked.
The published figure
Listing states pro-grade granular soda ash (sodium carbonate), sold in 5 and 10 lb pouches or a 25 lb bucket
Doheny's states granular soda ash - sodium carbonate - and lists 5 and 10 lb pouches alongside a 25 lb bucket, so the quantity can match the correction instead of the shelf.
The listing states the benefits in the usual terms: less equipment corrosion, less eye irritation, less skin dryness. Those are the three things acidic water actually does to a pool and the people in it.
It publishes no dose figure, which is normal for pH products - how much a pool needs depends on its total alkalinity, not on its volume alone.
What it does well
- Pouch sizes suit a single correction
- Stated granular soda ash, the standard pH increaser
- Cheapest way here to buy a known quantity
What it costs you
- No dose figure published
- No purity percentage stated on the listing
- Third-party seller, so delivery times vary
Skip it if your total alkalinity is also low. Sodium bicarbonate fixes both readings at once and soda ash does not.
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Pick 4 - Raising total alkalinity
Pool Mate Premium Alkalinity Increaser, 10 lb
100% sodium bicarbonate and it says so, which is the only claim that lets you compute the dose yourself.
The published figure
Listing states 100% sodium bicarbonate
Alkalinity increaser is sodium bicarbonate. Every brand sells the same compound, and the only thing worth checking is whether the label admits it.
Because this one states 100% purity, the arithmetic below applies exactly: 1.4 lb raises 10,000 gallons by 10 ppm.
Raise alkalinity before pH. Alkalinity is what stops pH bouncing, so correcting pH first means correcting it again.
What it does well
- States 100% purity, so the dose is computable
- Sold in a size that matches a real correction
- Cheapest per ppm of the balancers here
What it costs you
- Raises pH slightly as a side effect
- Needs a full circulation cycle before retesting
Skip it if your alkalinity is already above 120 ppm — you need acid, not bicarbonate.
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Pick 5 - A season of corrections on an acidic pool
In The Swim pH Increaser for Pools, 25 lb
The bulk tub, and the only listing here that admits plainly that soda ash raises alkalinity as well as pH.
The published figure
Listing states sodium carbonate, raises both pH and total alkalinity, target pH 7.2-7.6
In The Swim states the product raises both total alkalinity and pH. That is the honest description of soda ash and the reason it is the wrong tool when alkalinity is already at the top of its range.
The listing gives the target as 7.2 to 7.6 and puts real numbers on the consequences either side: above 8 risks skin rashes, below 7 stings eyes.
25 lb is a lot of soda ash. It suits a pool fed by trichlor tablets or dosed with acid regularly, where pH drifts down all season - not a pool correcting once.
What it does well
- States that it moves alkalinity as well as pH
- Publishes the 7.2-7.6 target and what happens outside it
- Bulk size for a pool that drifts acidic every month
What it costs you
- No dose figure published
- 25 lb is far more than a one-off correction needs
- Raising alkalinity is a side effect you may not want
Skip it if you need one correction. A 5 or 10 lb pouch costs a fraction and does not sit in the shed absorbing damp.
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Pick 6 - Pool owners who already know why they want borate
20 Mule Team 20 Mule Team Borax Detergent Booster, 65 oz
The unlabeled route. Borax does raise pH with less effect on alkalinity than soda ash, and nothing on this box says a word about pools - which is the caveat, not a secret.
The published figure
Laundry product: the listing states only that it is a multipurpose household cleaner that makes detergent work better, and makes no pool claim at all
This is a laundry booster. The listing states that it is a multipurpose household cleaner which makes detergent work better - and that is the whole specification. There is no pool dose, no pool target range and no pool claim anywhere on it.
Pool owners use it because sodium tetraborate nudges pH up while moving total alkalinity far less than sodium carbonate does, and because borate stays in the water as a mild buffer. Both of those are chemistry rather than label copy, and we are not going to print a dose the maker does not publish.
One practical consequence: borate does not show up on a standard test kit. None of the kits on this site includes a borate test, so a pool carrying borate is carrying something you cannot measure with the strips in your drawer.
What it does well
- Moves pH with less alkalinity movement than soda ash
- Stocked in most supermarkets, so it is easy to buy locally
- Sold in a size that lasts, at supermarket prices off Amazon
What it costs you
- Not labeled for pools, so there is no published dose or target
- No kit on this site tests for borate, so the level is unmeasured
- Third-party sellers price it well above supermarket shelf price - check before ordering
Skip it if you want a product with instructions on it. Buy soda ash, which is labeled and dosed for exactly this job.
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Pick 7 - The acid demand test
Taylor Technologies K-1004 DPD 6-in-1 Pool Test Kit
Includes an acid demand test, which is the only honest way to know how much pH reducer your pool needs.
The published figure
DPD kit including acid and base demand titrations
How much acid a pool needs to move pH from 8.0 to 7.5 depends on its total alkalinity, and no chart can tell you without knowing it. An acid demand test measures it directly.
That is why this site does not print a pH-down dose table: the number is a property of your water, not of the product, and the test costs a few dollars.
Six parameters rather than nine, so it does not cover cyanuric acid or salt.
What it does well
- Acid and base demand titrations, which most kits omit
- Cheaper than the nine-parameter kits
What it costs you
- No cyanuric acid test
- No salt test
Skip it if you need a cyanuric acid reading — that is a common problem this kit cannot see.
What we could not verify
How far a pound of soda ash moves pH in your pool - no maker publishes it, because it depends on alkalinity rather than volume. Purity percentages: Pool Mate and Leslie's both state 100% sodium carbonate in their titles, while Doheny's and In The Swim state the compound without a percentage. And any pool dose for borax, which is sold here as a laundry product and labeled accordingly.
Questions people actually ask
How do I raise the pH in my pool?
What causes low pH in a pool?
Can I use baking soda to raise pool pH?
Is borax good for raising pool pH?
Why is there no dose chart for pool pH?
Is low pH worse than high pH?
How long before I retest after adding pH increaser?
Sources
Every figure on this page traces to one of these. Where a number could not be sourced, the page says so rather than estimating.
- HTH Pool Care pH Down - product page, sodium bisulfate, states a 7.2-7.6 target and a 4-6 hour wait after shocking
- Pool & Hot Tub Alliance - PHTA standards program, the ANSI-accredited consensus standards for residential and public pools
- Skim & Soak methodology - the constants, formulas and worked examples behind every dose on this site
- Pool Mate Premium pH Up, 10 lb, 100% sodium carbonate - Amazon listing, read 2026-09-21
- Leslie's Soda Ash pH Up, 10 lb, 1 lb per 10,000 gal and a 4 lb single-dose cap - Amazon listing, read 2026-09-21
- Doheny's pH Plus granular soda ash - Amazon listing, read 2026-09-21
- In The Swim pH Increaser, 25 lb, states it raises alkalinity and pH - Amazon listing, read 2026-09-21
- 20 Mule Team Borax Detergent Booster, 65 oz - no pool claim on the label - Amazon listing, read 2026-09-21
- Taylor K-1004 DPD 6-in-1 kit with acid and base demand titrations - Amazon listing, read 2026-09-21
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