How much stabilizer to add to your pool

13 oz (382 g) of granular stabilizer raises cyanuric acid by 10 ppm in 10,000 gallons. Most manually chlorinated pools aim for 30 to 50 ppm; salt water pools 60 to 80.

Stabilizer (CYA) calculator

Add

3.8lb

of Stabilizer granules (cyanuric acid 99%)

61 oz1.7 kg

Raises CYA from 10 ppm to 40 ppm in 15,000 gal.

Also raises cyanuric acid (stabilizer). It only comes down by replacing water.
Put the granules in a sock in the skimmer basket or in front of a return. Do not backwash for a week.
Stabilizer takes several days to dissolve and register on a test. Do not add more in the meantime.
At CYA 40 your free chlorine minimum becomes 3 ppm and the target 6 ppm.
Adding too much is hard to undo: only draining lowers CYA. If unsure, add three quarters, wait a week and retest.

Check the product label. Strengths vary by brand, so enter the % printed on yours. Add one chemical at a time, into the water, and never mix chemicals.

Save this test and get reminded when it is time to retest.

Pool Calc for iPhoneComing soon to the App Store

How to add it

Put the granules in an old sock or a mesh bag in the skimmer basket, or hang it in front of a return.
Leave the pump running. Squeeze the sock now and then.
Do not backwash or clean the filter for about a week.
Retest after a week. CYA dissolves slowly and takes days to show fully.

Liquid stabilizer dissolves at once but costs more per ppm.

Too much is hard to undo

Nothing you can add lowers CYA; only replacing water does. Dichlor and trichlor add stabilizer every time you use them (0.9 and 0.6 ppm of CYA per ppm of chlorine), so tablet-fed pools creep up all season. If you are near your target, add three quarters of the dose and retest.

Questions

How much stabilizer for a 15,000 gallon pool?

About 1.3 lb per 10 ppm, so 5.1 lb from 0 to 40 ppm.

How do I lower stabilizer?

Drain part of the water and refill. The drain and refill calculator shows how much.

Do salt water pools need stabilizer?

Yes, usually more: 60 to 80 ppm, because the cell produces chlorine continuously.