Pool & spa
Pool Stabilizer Calculator
Doses stabiliser, which is cyanuric acid under its other name.
Result
Dose against a test result, never against a schedule. Add chemicals in stages with the pump running, wait for a full turnover, then retest before adding more. Never mix chemicals, and never add water to acid. Where a product label differs from the figure here, the label wins. Stabiliser dissolves slowly and is usually added through the skimmer sock rather than broadcast. It can take a week to register fully on a test, so retest before adding more or you will overshoot a level you cannot easily bring back down.
Get a Free Business AuditHow the calculation works
Stabiliser, conditioner and cyanuric acid are the same thing under different names on the shelf, and the dose is the gap to target times the volume. It dissolves slowly, which matters practically: added to the skimmer or a sock rather than broadcast, and it takes time to register on a test, so retesting too soon shows a lower figure than has actually been added and invites over-dosing.
What moves the number
- Gap to target and volume, as with any dose.
- How it is added, since it dissolves slowly and can damage surfaces if dumped.
- Whether stabilised chlorine products are already contributing.
- Whether the pool is a salt system, which typically targets higher.
Where this one goes wrong
Retest only after it has fully dissolved, which takes longer than most chemicals. Testing a day after adding stabiliser and seeing little change tempts a second dose, and since the level can only be reduced by draining, that over-dose is expensive. Add it in the skimmer or suspended in a sock, give it time, then test. Do not broadcast undissolved granules onto a vinyl liner or coloured plaster, because sitting granules can bleach and damage the surface. And check what your chlorine product is already adding before dosing stabiliser at all.
Before you quote
- Allow full dissolution before retesting, to avoid double dosing.
- Add via the skimmer or a sock rather than broadcasting.
- Check whether stabilised chlorine is already raising the level.
Where the rules come from
Questions
About this calculator
Is stabiliser the same as cyanuric acid?
Yes. Stabiliser, conditioner and cyanuric acid are the same chemical sold under different names, which causes genuine confusion when an owner adds both thinking they are different products. That is one of the easier ways to over-stabilise a pool.
Why does my stabiliser reading not change after dosing?
Because it dissolves slowly and takes time to register. Testing too soon shows less than was added and tempts a second dose, which is a problem since the level can only be lowered by draining. Allow full dissolution before retesting.
Can I broadcast stabiliser into the pool?
Better not to. Undissolved granules sitting on a vinyl liner or coloured plaster can bleach and damage the surface. Adding it through the skimmer or suspended in a sock lets it dissolve in circulation without resting on anything.
The formula
about 0.85 lb per 10,000 gallons raises stabiliser 10 ppm
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How to use this calculator
- Pool volume (gallons). Enter your own figure; the page starts at 20,000.
- Current stabiliser (ppm). Enter your own figure; the page starts at 10.
- Target stabiliser (ppm). Enter your own figure; the page starts at 40.
- Price per pound or gallon ($). Enter your own figure; the page starts at $3.2.
The result updates as you type, so you can try a figure, see what it does to stabiliser to add, and change it back. Nothing you enter is sent anywhere or saved.
A worked example
These are the figures the calculator opens with. Every number in the results column below is produced by the same calculation the page runs, so you can follow it through before putting your own figures in.
What goes in
| Input | Value |
|---|---|
| Pool volume (gallons) | 20,000 |
| Current stabiliser (ppm) | 10 |
| Target stabiliser (ppm) | 40 |
| Price per pound or gallon | $3.2 |
What comes out
| Result | Value |
|---|---|
| Stabiliser to add main result | 5.1 |
| Change needed | 30.0 |
| Estimated cost | $16.32 |
| Dose per 10,000 gallons | 2.6 |
Add about 5.1 to move 20,000 gallons from 10 to 40.
How sensitive the answer is
Holding everything else steady and changing only price per pound or gallon, this is what happens to stabiliser to add. It is worth knowing which of your inputs the answer actually hinges on, and which barely move it.
| Price per pound or gallon ($) | Stabiliser to add |
|---|---|
| $1.6 | 5.1 |
| $2.4 | 5.1 |
| $3.2 example above | 5.1 |
| $4.8 | 5.1 |
| $6.4 | 5.1 |
Every other input is held at the example value while this one changes, which is not how a real job behaves. Treat it as a guide to which number matters most, not as five separate quotes.
What each figure means
- Pool volume (gallons)
- A number, between 0 and 2000000, starting at 20,000.
- Current stabiliser (ppm)
- A number, between 0 and 200, starting at 10.
- Target stabiliser (ppm)
- A number, between 0 and 200, starting at 40.
- Price per pound or gallon ($)
- A money amount, starting at $3.2.
What the results tell you
| Result | What it is |
|---|---|
| Stabiliser to add | The headline result. A decimal figure. |
| Change needed | A decimal figure. |
| Estimated cost | A money figure. |
| Dose per 10,000 gallons | A decimal figure. |
Estimating is the easy part
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