Saltwater Pool Chemicals

A salt pool runs on five things: salt, muriatic acid, cyanuric acid, a shock product, and a test kit that actually measures. Everything else on the shelf is optional, a repackaged version of one of those five, or something to actively avoid.

The five you keep on hand

That is the cabinet. HomeGuide puts DIY saltwater maintenance at about $45 a month, and most of that is acid and the occasional bag.

Salt

Sodium chloride, nothing else. Hayward’s manual asks for “only sodium chloride (NaCl) salt that is greater than 99% pure,” names the acceptable types as “common food quality or water softener salt,” and adds that “it is also acceptable to use water conditioning salt pellets.” The Trouble Free Pool wiki points at solar salt sold for water softeners at 99.4% or better, no rust inhibitor or other additives, and notes that pool store salt generally costs more for the same thing.

What must not be in the bag is short enough to memorize, and it is Hayward’s: “Do not use rock salt, salt with yellow prussiate of soda, salt with anti-caking additives, or iodized salt.”

A 40 lb bag raises 10,000 gallons by roughly 480 ppm, against Hayward’s target of “between 2700-3400 ppm (parts per million) with 3200 ppm being optimal.” For most pools that is several bags at startup and almost nothing for years, because salt is not consumed and only leaves with water. Buying guide on pool salt, dose on the pool salt calculator.

Muriatic acid

The workhorse. pH climbs in every salt pool because hydrogen gas from the cell aerates the water and drives off carbon dioxide, which Orenda identifies as the real mechanism rather than the sodium hydroxide explanation that gets repeated. Acid is a recurring purchase, not a corrective one. Hayward’s pH target is 7.2 to 7.8. Buy the big jug rather than pH-down granules in a tub with a pool logo on it.

Acid does a second job here. When the cell scales badly enough that a hose will not clear it, Hayward’s instruction is a 4:1 solution of water to muriatic acid, soaked “for a few minutes,” then rinsed. The safety rule is in capitals in the manual and belongs in capitals here: ALWAYS ADD ACID TO WATER, NEVER ADD WATER TO ACID. Never use metal tools between the plates, because they scratch the coating. Procedure on how to clean a salt cell.

Cyanuric acid

Sold as stabilizer or conditioner, usually a white granular. It shields free chlorine from sunlight, and a salt pool needs more of it than a chlorine pool because the cell trickles chlorine in continuously rather than delivering a slug each morning.

The two authorities do not quite agree. Trouble Free Pool recommends 60 to 90 ppm for a salt water chlorine generator pool against 30 to 60 ppm for a liquid chlorine pool. Hayward’s chart asks for 60 to 80 ppm with 80 as the target. Follow your own manufacturer, because that is what the warranty is written against.

HTH’s instructions give 1 lb per 10,000 gallons for about 10 ppm, so a 20,000 gallon pool needing 30 more ppm takes 6 lbs. Add it slowly to the skimmer with the pump running, and do not backwash for 48 hours. It dissolves slowly, so wait 24 to 48 hours before retesting, and retest pH and alkalinity too, because cyanuric acid is mildly acidic.

Be careful, because the way back down is expensive. Orenda’s position is that only two things work: draining and diluting, “the most economical and practical way,” and reverse osmosis. Add slowly, retest, add again. More on salt water pool stabilizer and cyanuric acid for pools.

Shock

Granular cal-hypo or liquid chlorine, per In The Swim, at 3 lbs per 10,000 gallons or 5 gallons per 10,000 gallons for a full shock. Buy one or the other, and buy it when you need it, since liquid loses strength on the shelf.

Do not buy a stabilized shock for a salt pool, because it brings cyanuric acid into a pool already running high on it. And do not assume the boost button replaces this product. It does not, and that is covered on salt water pool shock.

A test kit that measures

The one place to spend more than you want to. Strips get you in the neighborhood on pH and chlorine and will not reliably tell you what salt or cyanuric acid are doing, and those are the two numbers that decide everything else here.

Get a drop-based kit with a salt titration test, so you have a salinity number independent of your control panel. That independence is the point. The panel infers salinity from how easily current crosses the cell, so a scaled cell, worn plates, cold water or the wrong cell model set in the menu all move the displayed number while no salt moves anywhere. Poolside describes most systems as estimating “salt levels using an algorithm” rather than reading salinity directly, and Orenda recommends verifying with a separate salinity meter, since a faulty sensor can read lower than the actual level. Without your own test you cannot tell a low salt pool from a lying panel, and the two get treated very differently on salt levels and testing.

What the store will sell you that you do not need

Salt cell cleaner. Dilute acid in a bottle with a picture of a cell on it. Hayward’s own instruction is 4:1 water to muriatic acid, which you already own.

Chlorine tabs. The worst purchase for a salt pool. Orenda’s number: “trichlor is only 45.8% chlorine (by weight). The majority of it is cyanuric acid.” Tabs push a salt pool past its stabilizer range and the only way back is water.

Cyanuric acid reducers. Orenda’s summary is that “some CYA reducers are on the market, but our customers have told us their results are mixed.” Nitrifying bacteria cannot survive in chlorinated water, and alum results are mixed. Draining is what works.

Pool-branded salt at a premium. Same sodium chloride, higher price, per the Trouble Free Pool wiki.

Weekly algaecide as prevention. Algae here is nearly always chlorine too low for the stabilizer level, not a missing product. If the water is already cloudy, work through cloudy salt water pool rather than buying a bottle.

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