High CYA & High Metals: Fred Schweer’s Fix-It Formula

Many pool owners chase chlorine levels and still end up with cloudy water, stains, or persistent algae. The real story often lives in two quiet variables: dissolved metals and cyanuric acid. This episode dives deep into how Pool RX reduces chlorine demand while preventing algae, and why testing for copper and iron before installation protects you from oxidation events and staining. We explain how chelated minerals in Pool RX are protected, but existing metals in the water are not, and how increased chlorine activity can push unchelated metals over their saturation point. The result can be brown iron stains or purple-black copper reactions that look like a product failure but actually trace back to hidden metal loads.

Testing for metals does not need to be complicated or constant, but it does need to be smart. If your region uses well water, has aging copper heat exchangers, or a history of copper-based algaecides, annual testing for copper and iron is an inexpensive insurance policy. Tools like copper test strips or a photometer such as the LaMotte ColorQ 2X Pro 9 give you a snapshot that helps you plan. If metals read high, remove them before installing Pool RX. Options include polymer capture like the CuLator bag, which physically binds trace metals as water flows through, or approaches like alum floc to drop metals out for vacuuming. Sequestering agents can help but break down under chlorine and time, so they require ongoing dosing and don’t actually remove metals from the system.

High cyanuric acid complicates the picture. CYA protects chlorine from sunlight, so it lasts longer but kills slower. Pool RX shines here by targeting microalgae, freeing that slower chlorine to focus on clarity and sanitation. The catch is water balance. Cyanuric acid distorts what your alkalinity reading seems to be, which is why adjusted, or carbonate, alkalinity matters. As a rule of thumb near pH 7.4, when CYA exceeds 100 ppm, your true alkalinity can be roughly one third lower than the test shows. That means a reading of 90 might functionally be 60, which increases the risk of out-of-balance water and strange side effects like copper cyanurate forming a purple dust on scaled surfaces.

Keeping balance within standard ranges helps avoid costly surprises: pH about 7.2 to 7.8, calcium hardness 200 to 400 ppm, and alkalinity 80 to 120 ppm after adjustment for CYA. If your alkalinity is truly low, fix it with sodium bicarbonate; a pound and a half per 10,000 gallons raises about 10 ppm without chasing pH. When CYA creeps up to 150 or 200, teach clients why fresh water is the cleanest fix. If draining is off the table, you can slow the rise and even trend it down by switching from heavy tablet use to liquid chlorine while running Pool RX to keep algae suppressed. Seasonal dilution from rain and top-offs then nudges CYA lower without a full drain.

Purple dust is often copper cyanurate signaling imbalance and saturation, not a failure of mineral technology. The fastest path out is to reduce cyanuric acid toward 30 to 40 ppm and confirm alkalinity is truly in range after adjustment. If metals were high at the start, remove them before installing Pool RX. Note that strong chelation in Pool RX can mask copper readings; post-install tests may show zero or elevated copper regardless of the actual safe, chelated level. Don’t chase that number blindly; focus on pre-install tests and on-water behavior. With the right sequence—test, remove metals if needed, install Pool RX, balance pH, alkalinity, and calcium—you leverage more active chlorine, fewer tablets, and steadier clarity with less work.

This approach also extends water life. Using Pool RX often reduces chlorine demand by 40 to 50 percent, which means fewer tablets and a slower CYA climb. That translates into fewer algae events, easier brushing and filtration, and lower risk of staining from oxidized metals. For pros, it builds trust with clients who want clean water without frequent drains. For homeowners, it means fewer chemicals, simpler upkeep, and less guesswork. The key is respecting the sequence and the math: confirm metals are in line, account for CYA’s effect on alkalinity, and let Pool RX take the algae load off chlorine. When chemistry aligns, the pool looks better, costs less, and stays that way longer.