DI Water Calculator
How much DI water will you get?
Enter your source water TDS and rinse habits to estimate total gallons of deionized water and the number of washes per cartridge set.
How to test your TDS
Estimated System Outputs
Estimates assume 1 cubic ft of resin can remove approximately 200,000 ppm of dissolved solids, based on a constant 2 gpm rinse. Actual results vary with water chemistry, temperature, and rinse technique. Replace the DI cartridge as soon as your TDS meter reads above zero while water is flowing.
How to test your TDS
TDS varies block to block and season to season, so test your own water rather than guessing from a zip code.
With a Spotless system
- Shut off water supply.
- Unscrew the blue housings with wrench.
- Remove resin cartridges from housings.
- Screw housings back in with wrench.
- Turn water on.
- Pull trigger/nozzle on the flat or center setting on your provided hose nozzle and read the TDS reading while water flows. This is your PPM.
- Remember to reinstall your resin cartridges before next use.
No system yet?
Use any handheld TDS meter: fill a clean cup from your outdoor spigot, dip the probe, and read the ppm value. That number is all you need below.
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What is your resin actually doing?
Tap water carries dissolved minerals and salts such as calcium, magnesium, sodium, potassium, chloride and more, measured as TDS (total dissolved solids) in parts per million. Those dissolved minerals are exactly what gets left behind as spots when water evaporates off a clean vehicle.
Our DI (deionization) resin is a mix of two resin types that act like tiny magnets for those minerals: one swaps out the positively charged ions (like calcium and magnesium), the other swaps out the negatively charged ions (like chloride and sulfate). What comes out the other side is water stripped of essentially everything except hydrogen and oxygen, leaving H2O and nothing else.
Pure H2O in, spot-free rinse out
The higher your TDS, the more work the resin does per gallon, which is why 500 ppm water burns through resin roughly twice as fast as 250 ppm water, and why no single flat gallon number applies to everyone. That’s what this calculator solves for your actual water.
* Your TDS reading may change throughout the year due to season, rainfall, and water source. All outputs are estimates and actual results may vary.
Cross-check the formula
1 cubic ft of resin can remove approximately 200,000 ppm of dissolved solids.
200,000 ÷ TDS (ppm) = gallons from 1 cubic ft of resinThen multiply by the resin volume of your system.
