How to Raise Cyanuric Acid Level in Your Pool?

Add granular chlorine stabilizer, which is cyanuric acid. HTH’s rate is 1 lb per 10,000 gallons for about 10 ppm, added slowly to the skimmer with the pump running, and then you leave the pump running and do not backwash for 48 hours. It dissolves slowly, so wait 24 to 48 hours of circulation before you retest.

That is the whole job. The rest of this page is about getting the dose right the first time, because this is a chemical that is expensive to remove. What CYA does is on cyanuric acid for pool.

Step 1: get your actual volume

Every dose here is a rate per gallon, so a wrong volume produces a wrong dose in exact proportion. A pool the owner calls 20,000 gallons that is really 16,000 gets a 25% overdose. Measure once with the pool volume calculator and write the number inside the equipment pad door.

Step 2: test, and know your target

Test CYA before you add anything. Stabilizer only leaves with water, so the number should be close to where you left it, but backwashing, splash-out and rain all pull it down. Targets, so you know the gap you are closing:

The standard CYA test is a turbidity test judged by eye, so read it in consistent light and call the endpoint the same way each time. It is not a precision instrument, which is a reason to aim for the middle of a range rather than an exact number.

Step 3: work out the dose

pounds of stabilizer = (gallons ÷ 10,000) × (ppm you want to gain ÷ 10)

Worked example. An 18,000 gallon salt pool tests at 35 ppm and you want 75 ppm. The gain is 40 ppm, so the dose is 1.8 × 4 = 7.2 lbs. Round down to 7, not up to 8.

Aim for the low end of your range on the first dose. Coming back up is one afternoon. Coming back down means replacing thousands of gallons, which is laid out on reduce cyanuric acid swimming pool.

Step 4: pick a method

Granular cyanuric acid does not dissolve quickly, and every method below is a way of managing that.

Into the skimmer, slowly, pump running. The method HTH’s own label describes. Add a little at a time with water moving so the granules get pulled into circulation. Fastest, and the method that puts the most undissolved material into your filter.

The sock method. Put the measured dose in a clean sock or fine mesh bag, tie it off, and hang it in the skimmer basket or in front of a return jet. Squeeze it every few hours. Slower, but nothing undissolved reaches the filter and you can pull it out if you change your mind. With a cartridge filter, or a large dose, this is the safer choice.

Pre-dissolve in a bucket. Warm water and a lot of stirring, then pour the slurry around the pool with the pump running. Keep stirring until the granules are gone rather than dumping the last of it in one spot.

What not to do is broadcast it across the pool floor. It sits where it lands and dissolves unevenly, and on a vinyl liner you do not want undissolved chemical resting on the surface.

Step 5: run the pump and leave the filter alone

HTH’s instruction is explicit: leave the circulation pump running and do not backwash for 48 hours. Backwash on day one and the undissolved stabilizer sitting in your filter goes out to waste, and your dose is now unknown. Same logic for cleaning a cartridge in the first two days.

Step 6: retest at 24 to 48 hours, not before

This is the step that causes overdoses. HTH says to wait 24 to 48 hours of circulation before retesting. Test at four hours and you will read well below target, conclude the dose was short, add more, and watch the whole lot dissolve over two days into a number you cannot easily undo. Give it the full 48 hours if you dosed heavily, then add the remainder if there is one.

Retest two other things. Cyanuric acid is mildly acidic, so HTH advises checking pH and alkalinity after a large dose. In a salt pool pH is usually climbing anyway, so a nudge down may save you an acid addition. When you do need to bring pH back, that is on muriatic acid for saltwater pool.

Step 7: reset your chlorine target

Trouble Free Pool’s point is that the free chlorine level you must maintain depends on your CYA level and rises as CYA rises, and if FC drops too low for your CYA you get algae. So the job is not finished when the CYA test reads right. Set the new target using optimal chlorine levels saltwater pool, then adjust output and pump hours to hold it. The usual outcome after fixing a low CYA is that you can turn the output percentage down, because less of what the cell makes is being destroyed.

The mistakes that actually happen

• Dosing against a guessed volume. The biggest one, and the easiest to fix.
• Retesting at four hours and dosing again. The most common route to 120 ppm.
• Backwashing inside 48 hours. Your dose leaves the property.
• Aiming for the top of the range. Aim low, top up.
• Raising CYA with trichlor on purpose. It works, since trichlor is mostly cyanuric acid, but you cannot control the dose and you are adding chlorine you may not need.
• Treating a low CYA reading as a cell fault. Low chlorine with a healthy panel is a chemistry symptom first. Check CYA before you price a cell at salt cells and water care.

Where to go next