Use G3-N1CF for the first stage, G3-N3CB for carbon, and WD-G3-N2RO for the 400 GPD RO membrane. The RO membrane is currently $92.99 with a 24-month / 2,200-gallon rating.
Correct cartridges
Waterdrop identifies G3-N1CF and G3-N3CB for the G3 family, plus WD-G3-N2RO for the 400 GPD G3P400 system.
Replacement intervals
CF is typically up to six months, CB up to 12 months and WD-G3-N2RO up to 24 months under manufacturer guidance.
Current membrane price
WD-G3-N2RO is currently listed at $92.99 one-time, with subscription pricing sometimes lower.
Annualized core-filter cost
Using current list prices and nominal schedules, the three core cartridges annualize to about $136 per year.
How to verify fit before buying Waterdrop G3 / G3P400 Replacement Filters: Exact Cartridge Guide
Treat compatibility as a model-number decision, not a shape-matching exercise. Start with the appliance or system model label, then confirm the exact cartridge or replacement code listed by the manufacturer. Similar-looking filters can use different tabs, seals, RFID features or bypass interfaces, so a cartridge that appears to fit can still leak, restrict flow or fail to lock correctly.
For aftermarket replacements, separate physical compatibility from filtration performance. A seller can correctly state that a cartridge fits a refrigerator while the contaminant-reduction scope differs from the original filter. If lead, cysts, PFAS or another health-related claim matters, verify the exact replacement model in the current certification or performance documentation rather than assuming an OEM-equivalent claim set.
Compare recurring cost, availability and replacement risk
Replacement products should be evaluated over several service cycles. Multiply the current cartridge price by the realistic replacement frequency, add shipping, and check whether the same model is consistently stocked. A low first-purchase price is less useful if the cartridge becomes difficult to source or if replacement intervals are short.
Watch for vague phrases such as “uses certified media” or “tested to a standard.” Finished-product certification is stronger evidence than a statement about one component. For marketplace listings, clear manufacturer identity, exact model numbers, return policies and traceable certification reduce the risk of counterfeit-style or poorly fitting replacements.