How Often to Change Reverse Osmosis Filters (and What It Costs Per Year)

Short answer: most RO systems follow a 6 / 12 / 24 rhythm: pre-filters every 6 months, carbon post-filters every 12 months, and the RO membrane every 24 months. Replace sooner if you reach the gallon rating first. Your real yearly cost is each filter's price × the number of replacements per year, and for heavy users the gallon limit, not the calendar, sets that number.

Published October 1, 2026. Schedules below come from each manufacturer's manual, data sheet or product page. We don't publish our own price estimates because filter prices change constantly. Where a manufacturer publishes an annual cost, we quote it with the date. We don't run a lab.

Why each stage has its own schedule

• Sediment / pre-filter: catches grit and rust. It clogs fastest, especially on well water.
• Carbon pre- or post-filter: removes chlorine, which can damage RO membranes, and improves taste. Once it's exhausted, chlorine reaches the membrane.
• RO membrane: the expensive part. It lasts longest if the pre-filters are changed on time.
• Specialty stages (UV, remineralization): follow their own schedule in the manual.

Schedules by model

Waterdrop G3P800 / G3P600 (tankless under-sink), per Waterdrop:

• Composite pre-filter (CF): every 6 months or 550 gallons
• Carbon block (CB): every 12 months or 1,100 gallons
• RO membrane: every 24 months or 2,900 gallons

AquaTru Carafe (countertop), per AquaTru's data sheet:

• Pre/carbon filter: every 6 months or 300 gallons
• VOC filter (or VOC with pH+ Mineral Boost): every 12 months or 300 gallons
• RO membrane: every 24 months or 600 gallons. The Amazon listing for the alkaline bundle says 1 year, so follow your unit's indicator.

APEC ROES-50 (tank under-sink), per its listing: APEC recommends replacing filters every 6 to 24 months depending on incoming water quality. Check the manual for the stage-by-stage schedule.

Any other system: look for both a months and a gallons figure for every stage. If a manufacturer gives only months, ask what capacity that assumes.

How to work out your cost per year

1. Estimate your yearly use. Gallons of filtered water per day × 365. A household that drinks and cooks with 2 gallons a day uses about 730 gallons a year.
2. For each filter, find replacements per year. Take the larger of (12 ÷ months rating) and (yearly gallons ÷ gallon rating).
3. Multiply by that filter's current price, then add up all the stages.

Worked example at 730 gallons a year

Waterdrop G3P800:

• Pre-filter: 12 ÷ 6 = 2 by time; 730 ÷ 550 ≈ 1.3 by gallons. 2 per year.
• Carbon block: 12 ÷ 12 = 1; 730 ÷ 1,100 ≈ 0.7. 1 per year.
• RO membrane: 12 ÷ 24 = 0.5; 730 ÷ 2,900 ≈ 0.25. 0.5 per year (one every two years).

AquaTru:

• Pre/carbon: 12 ÷ 6 = 2; 730 ÷ 300 ≈ 2.4. About 2.4 per year.
• VOC: 12 ÷ 12 = 1; 730 ÷ 300 ≈ 2.4. About 2.4 per year.
• RO membrane: 12 ÷ 24 = 0.5; 730 ÷ 600 ≈ 1.2. About 1.2 per year.

The lesson: at this usage, the AquaTru's gallon limits drive replacements well above its calendar schedule, while the G3P800 stays on its calendar. Light users (well under 1 gallon a day) will see the AquaTru follow its calendar too. Multiply these counts by current filter prices for your own number.

Published annual cost figures

Waterdrop's own comparison chart listed an "average annual cost" of $159.97 for the G3P800 and $144.97 for the G3P600 on October 1, 2026. These are the manufacturer's figures, not ours. They assume the calendar schedule, and they will change with Waterdrop's pricing.

Signs a filter needs changing early

• The TDS reading rises on a smart faucet or handheld meter. The membrane is losing rejection.
• Production slows. AquaTru, for example, says to replace the RO filter if one tank takes longer than 30 minutes.
• Taste or odor returns. The carbon is exhausted.
• Your water changed. Hard, iron-bearing or high-sediment water (common on wells) shortens every stage. See RO for well water.

Cheap ways to make filters last

• Change pre-filters on time. They protect the membrane, the most expensive part.
• On a well or very hard water, treat upstream (sediment, iron, softening) so the RO isn't doing that work.
• Flush the system as the manual directs after every filter change.
• Use genuine or certified-compatible filters. Certified claims apply only to the certified configuration.

For general cleaning and sanitizing, see our RO maintenance guide.

Frequently asked questions

How often should you change reverse osmosis filters?

As a rule of thumb: sediment/carbon pre-filters every 6 months, carbon post-filters about every 12 months, and the RO membrane every 2 years, or sooner if you hit the gallon rating first. Always follow your model's manual. For example, Waterdrop lists 6 / 12 / 24 months for the G3P800, and AquaTru lists 6 / 12 / 24 months with lower gallon limits.

How do I know my RO membrane needs replacing?

Signs include a rising TDS reading on a smart faucet or TDS meter, slower production, or a change in taste. AquaTru, for example, says to replace the RO filter if one tank takes longer than 30 minutes to filter.

How much do RO filters cost per year?

It depends on the model and how much water you use. Add up each filter's price multiplied by how many times a year you will replace it, whether that is set by months or by gallons. Waterdrop's own comparison chart listed an average annual cost of $159.97 for the G3P800 and $144.97 for the G3P600 as of October 1, 2026. Prices change, so check on the day you buy.

Can I go longer than the recommended schedule?

We don't recommend it. Certified reduction claims are only valid within the rated capacity, and exhausted pre-filters let chlorine and sediment reach the membrane, which shortens its life.

Related guides

• Reverse osmosis maintenance guide
• How often to change any water filter
• Waterdrop G3P800 vs G3P600
• Waterdrop G3P800 vs AquaTru