How to test your pool water
What the four readings mean, how strips and drop kits differ, and why this page has no dose tables: we have no supplier and therefore no product labels to quote.
By NZ Swimming Pools
Key takeaways
- Four readings do most of the work: sanitiser level, pH, total alkalinity and, on a salt pool, salt.
- Strips are fast and cheap; a drop-test kit reads closer and does not depend on a faded colour chart.
- Test more often in summer, and after heavy use or heavy rain.
- This page gives no dose figures. A dose depends on the product's own label and your pool's actual volume, and we have no supplier and no labels to quote.
- Several New Zealand pool retailers test a water sample free in store: worth doing when your readings and the water disagree.
Take a sample from elbow depth, away from the returns, and read four things: the sanitiser level, pH, total alkalinity, and salt if you have a salt chlorinator. Strips give you all of them in about thirty seconds; a drop-test kit is slower and reads closer. If your own readings and the state of the water disagree, take a sample to a pool shop and let their meter settle it.
What each reading is telling you
- Sanitiser (free chlorine, or the equivalent for your system): whether anything in the water is actually killing what lands in it. This is the one that moves fastest in hot weather and after a busy afternoon.
- pH: how acidic or alkaline the water is. It affects both how well the sanitiser works and how the water feels on skin and eyes.
- Total alkalinity: the water's resistance to pH swinging. When alkalinity is wrong, pH will not hold still no matter what you add.
- Salt: on a salt pool, the raw material the chlorinator converts to chlorine. Salt is not consumed by chlorination, but it leaves with backwashing, splash-out and overflow.
Strips or a drop kit
| Test strips | Drop-test kit | |
|---|---|---|
| Speed | About 30 seconds | A few minutes |
| What you read | Colour pads against a printed chart | Reagent drops until the colour turns |
| Ageing | Go off once opened; check the expiry | Reagents also expire, but are less affected by a faded chart |
| Best for | Routine weekly checks | Working out why something is wrong |
How often
More often in summer than in winter, and after anything that changes the water: a pool full of kids, a storm, a big top-up, or a week away. Weekly through the swimming season is the habit most owners settle into.
Why there are no dose tables on this page
Because an honest dose needs two things we do not have: the label of the product actually in your shed, and your pool's real volume. We have no supplier and no products, so we have no labels to quote, and we are not going to publish a table of numbers you would tip into your pool on our say-so. Follow the label on the product you own, work out your volume properly, and use a pool shop's free water test when you are unsure.
What we do sell: nothing, yet
There is nothing for sale on this site. When a real supplier is signed, the pool care pages will list real products at real prices and name who supplies them. Chlorine and pool acid will not be among them: they are dangerous goods for courier transport, and they belong with a supplier who ships them under its own compliance.
Questions
How often should I test my pool water?
More often in summer and after heavy use or rain. Most owners test at least weekly through the swimming season.
Are test strips accurate enough?
For a routine weekly check, generally yes, as long as the tub is in date and has not been left open. When something is wrong and you need to know why, a drop-test kit or a shop test is worth the extra few minutes.
Will you tell me how much chlorine to add?
No. That depends on the product's own label and on your pool's actual volume and readings. We have no supplier and therefore no labels to quote, and guessing on your behalf would be worse than useless.
Published 16 September 2026, last updated 16 September 2026 by NZ Swimming Pools. Every figure and rule on this page is quoted from a source we read in full on the checked date. See our editorial policy.