Hayward AquaRite 900 Wrong Salt Reading: Instant vs Average, ppm vs g/L

What Salt Readings Actually Mean

The AquaRite 900 does not have a dedicated salinity probe. Instead, it infers salt level by measuring cell voltage and current. Lower salt means higher resistance, which the controller translates into an estimated salinity number.

The system tracks two values:

• Average salt: This is the default display number and changes slowly over time. It is used for Check Salt and High Salt warnings.
• Instant salinity: Visible in the diagnostic menu, this responds faster to real changes in the water and is useful for confirming your salt additions.

If you just added salt, the instant reading will update within hours, but the average may take a day or more to catch up unless you manually sync it.

Step-by-Step Troubleshooting

Check for metric display (g/L vs ppm)

If the salt display shows a decimal value like "3.20" or "2.85", the controller may be set to show grams per liter instead of parts per million.

1. Use the diagnostic menu to check the display units.
2. If you see g/L, remember that 1 g/L equals 1000 ppm. So "3.20" g/L is actually 3200 ppm.
3. If this is the issue and you want to switch back to ppm display, consult the manual for the button sequence to change units.

Compare average salt to instant salinity

1. Press the diagnostic button until you see the instant salinity value (it will show as a negative number in the diagnostic scroll).
2. Write down both the default average salt display and the instant value.
3. Test the pool water with a reliable salt kit or meter.

If your test kit matches the instant reading but not the average, the average is stale and needs updating.

Update the average salt reading

Most AquaRite 900 units allow you to manually sync the average salt display to the current instant reading:

1. With the unit running in Auto mode, use the diagnostic button to step to the instant salinity display.
2. Follow the button-and-switch sequence described in the manual to update the average. This typically involves moving the main switch while holding a button.
3. After the update, the average salt should closely match the instant value and your test kit.

Verify Turbo Cell type

An incorrect t code setting (t-3, t-5, t-9, t-15) will cause the controller to misinterpret cell behavior and display wrong salt levels.

1. Use diagnostics to view the current cell type setting.
2. Compare it to the model number on the physical cell label (TCELL925, TCELL940, etc.).
3. If they do not match, correct the t code using the diagnostic menu sequence.

After correcting the cell type, salt readings should become accurate within a few hours of operation.

Inspect and clean the cell

Heavy scale or debris changes how current flows through the cell, which can make the controller "see" incorrect salinity.

1. With power off, remove the cell and inspect for deposits.
2. If heavily scaled, perform an acid wash following the manual's procedure.
3. Reinstall the cell, restore power, and give the system a few hours to recalculate salt.

Test for board or cell failure

If salt readings remain wildly inaccurate after confirming units, cell type, and cleanliness:

• Check cell voltage and current in diagnostics. If they are far outside normal ranges even with correct chemistry, the cell or board may have failed.
• Swap in a known-good cell temporarily if available to rule out cell issues.
• If the problem persists with a good cell, suspect the main control board.

Common Parts That Fix This Problem

• Replacement Turbo Cell if the original is electrically degraded and giving false readings
• Replacement control board if salt calculations are consistently wrong with a known-good cell and correct settings
• Acid and cleaning supplies to remove scale that is skewing conductivity

Model-Specific Notes

• The AquaRite 900 can display in either ppm or g/L. Make sure you know which unit the display is using before panicking about a "low" reading.
• The instant salinity value in diagnostics is shown as a negative number (e.g., "-3200") to distinguish it from the average.
• Different cell models require different t codes. Always match the code to the installed cell.

How to Prevent Salt Reading Problems

• After adding salt, use the instant salinity diagnostic to confirm the new level before waiting for the average to update.
• Keep a log of cell type, installation date, and any settings changes so you can quickly verify configuration.
• Clean the cell regularly to prevent scale from distorting readings.
• Test salt with an independent kit at least monthly during pool season.