By Sarah Chen · environmental engineer · water, waste and everything that flows downhill

“My first RO membrane lasted three months before the sand in my dam clogged it, costing me a week of clean water.”

Stop fiddling with your RO system. It’s not a magic box. Skip maintenance and your water tastes like a swamp. Or worse: you’re drinking bacteria. Here’s how to keep it running on your off-grid setup.

Filter Changes: Do It Or Lose It

Pre-filters clog fast. Change them every 6 months. Or when your flow rate drops. No excuses.

• Sediment filter (5 micron): $15-$25. Bunnings, Mitre 10. Get the 10" size for most systems.
• Carbon filter (block): $20-$35. Same stores. Replace when taste/odour returns.
• Post-carbon filter: $25-$40. Often bundled. Don’t skip it.

Membrane Cleaning: Not Optional

RO membranes get gunked up. You’ll know: pressure drops, water slows, or you smell chemicals. Clean it every 6-12 months. Or when your system’s producing less than 50% of its rated output.

Steps:

1. Turn off water supply and drain the system.
2. Remove the membrane housing.
3. Use a dedicated RO cleaner (not vinegar or bleach). Mix 1 part cleaner to 5 parts water.
4. Flush the membrane with cleaner for 15 minutes. Then flush with clean water for 30 minutes.
5. Reinstall. Test flow rate.

Sanitisation: Kill The Bacteria

After cleaning or if you’ve had a power cut, sanitise. Bacteria love stagnant water. One batch of E. coli in your tank = you’re sick. Do this every 3 months.

How:

• Use 3% food-grade hydrogen peroxide (not bleach). Mix 10ml per 10L of water.
• Flush through the system for 10 minutes.
• Then flush with clean water for 30 minutes. No peroxide left in your tank.

Off-Grid Specific Tips

• Store filters in a dry shed. Humidity ruins them. Don’t leave them in the garage.
• Check your storage tank pressure. If it’s below 50 PSI, your system won’t work. Fix it before changing filters.
• Test your water monthly. Use a TDS meter ($20-$30 at Bunnings). If it’s above 200 ppm, your system’s failing.
• Never run the system dry. It destroys the membrane. Always have water in the tank.