How to Convert a Pool to Salt Water

Most pools convert to salt water without draining. River Pools says you won’t have to drain and refill, and Leslie’s says the same unless your TDS is already above 2,500 ppm. The job is five things in order: balance the water, install the generator, add salt, test, then switch the cell on.

Before you buy anything, read the section on what to check first. Some pools need more thought than others. For the wider topic, see the salt water pools hub.

The steps, in one order

River Pools and Leslie’s publish slightly different sequences. River Pools has you balance the water, install the chlorinator and check for leaks, add salt, then test. Leslie’s has you test the water, add salt with circulation running, install the generator, run the pump and check for leaks, then re-test and activate. The only real difference is whether salt goes in before or after the hardware. Either works, because the cell is not switched on until the end.

1. Test and balance. Bring the water to the targets in the table below.
2. Check TDS. If it is over 2,500 ppm, partially drain and refill first.
3. Install the generator with the power to the cell off. Run the pump and check every union for leaks.
4. Add salt with the pump running. Leslie’s says to add bags while the circulation system is running and brush the pool to speed dissolving.
5. Let it circulate. Keep the pump on “to finish dissolving the salt, but don’t turn on your salt system quite yet.”
6. Test salt, then switch on. Leslie’s activates the system only after a salt test confirms the level.

In The Swim gives the same rule for opening a salt pool each spring: the cell stays off until the water is balanced and the salt is in. A salt water pool start up kit follows the same order.

Pre-conversion targets

These are Leslie’s targets before salt goes in.

They line up with Hayward’s manual, which lists alkalinity 80 to 120, calcium 200 to 400 and stabilizer 30 to 50, with a wider pH band of 7.2 to 7.8. Metals at zero matters more in a salt pool, because corrosion is already on the list of things to watch.

When you do have to drain

TDS is the exception. Leslie’s says: “If your current TDS level is already above 2,500 ppm, you may need to take an extra step. We recommend partially draining and refilling the pool to bring the TDS levels down before converting your pool to salt.”

Cyanuric acid is worth checking for the same reason. If years of tablets have pushed it well past 50 ppm, Orenda says only dilution or reverse osmosis lowers it. A partial drain before conversion fixes both at once.

How much salt to add

Most pools run 2,700 to 3,400 ppm, with 3,200 ideal per Hayward’s manual. Check your own cell’s manual. You also need an accurate volume: the pool volume calculator gets you there.

Our formula is lb = (gallons x ppm) / 120,000, because 1 lb per 1,000 gallons raises salinity 120 ppm. Leslie’s publishes a different one: “8.375 x Salinity Increase ÷ 100 = Pounds of salt per 10,000 gallons.” Here is an 18,000 gallon pool going from zero to 3,200 ppm both ways:

That is twelve 40 lb bags either way. The two formulas agree within about half a percent, which is a good reason to trust both. The pool salt calculator does the sum for you.

Add less than the full amount at first. Leslie’s puts it plainly: “It’s always easier to add more salt later than it is to overdose the pool.” Bringing salt down is harder than adding it, as our guide to lowering the salt level shows.

Where the cell goes

Leslie’s says the cell “should be the last piece of equipment the water passes through before returning to the pool.” Plumbing detail is in how to install a salt cell.

Sizing the cell

Buy for your real volume, not the smallest unit that claims to cover it. Leslie’s warns that “A salt cell that’s undersized will have to work overtime to keep up with the demands of your pool, and it will often fail faster.” We walk through the numbers in what size salt cell do I need.

What it costs

Three sources, three answers:

They price different equipment and different installers. The spread is what you should expect to be quoted.

Salt itself is a small line. River Pools puts it at 25 to 63 cents per pound, so 480 lb costs 480 x $0.25 = $120 up to 480 x $0.63 = $302.40. HomeGuide’s $10 to $20 per 40 lb bag gives 12 x $10 = $120 up to 12 x $20 = $240. More detail is on the cost to install a salt water pool page.

Warranty

Check this before you buy. Leslie’s warns that converting may void the warranty from the manufacturer or your pool builder. Read your pool warranty, and your equipment warranties, and ask in writing if it is unclear.

What to check first

Metal. River Pools lists corroding metal parts as a drawback of salt. Look at ladders, rails, light rings and anything metal in the equipment pad.

Plaster. River Pools says salt wears plaster faster on concrete pools. River Pools builds fiberglass pools, so bear that in mind, but no source here says otherwise.

Stone. Travertine Mart reports unsealed natural travertine coping spalling after 2 years of daily salt exposure, and says an impregnating sealer gives reasonable protection for 5 to 10 years. It sells travertine, not sealer.

The full rundown of pool types is on can any pool be a salt water pool.

What changes after conversion

You add acid more often. A working cell gives off hydrogen, which aerates the water and pushes pH up. See how to lower pH in a salt water pool.

Stop using trichlor tablets. They are the 3 inch tablets automatic chlorinators use, and Orenda puts trichlor at only 45.8% chlorine by weight, with most of the rest cyanuric acid, so every one adds CYA. With a cell making chlorine, that CYA has nowhere to go but up, and only dilution or reverse osmosis brings it down.

Salt mostly stays put. Leslie’s says it only needs replenishing after backwashing, splashing or draining.

If you are still deciding whether to switch, the side by side comparison is on salt water pool vs chlorine.

Where to go next