5-Stage Reverse Osmosis Drinking Water System

Standard RO systems using a conventional membrane produce approximately 3–4 gallons of reject water for every 1 gallon of pure water produced — a 3:1 or 4:1 waste ratio. This reject water carries the concentrated contaminants that the membrane rejected. It drains slowly to your drain line and is not a sudden dump of water. For a household using 3–5 gallons of RO water per day (drinking, cooking, ice), this is typically 9–20 gallons of drain water per day — comparable to a short shower. High-efficiency membranes with 1:1 ratios are available at additional cost if water conservation is a priority.

Yes — RO removes calcium, magnesium, and other dissolved minerals along with contaminants, because the membrane does not selectively reject harmful vs. beneficial compounds. For a point-of-use system (under one sink) providing drinking and cooking water, this is generally not a health concern because most dietary minerals come from food, not water. However, if you prefer to retain minerals in your drinking water, we can discuss remineralization post-filters or recommend the Naturwise TAC system for whole-house scale prevention paired with an RO system just for cooking.

The four pre/post filter cartridges (Stages 1, 2, 3, and 5) should be replaced every 6–12 months depending on your source water quality. The RO membrane (Stage 4) typically lasts 2–3 years. We track your TDS rejection rate — when the membrane's rejection drops below 90% (meaning it's passing more contaminants), it's time for membrane replacement. We offer an annual filter change service where we replace all four cartridge filters and test your output TDS — making filter maintenance completely hands-off for you.

Whole-house RO is technically possible but is uncommon in residential settings for several reasons: (1) the flow rate of RO membranes is relatively low — a 75 GPD membrane produces only about 3 gallons per hour — making it impractical to supply a whole house's peak demand; (2) the cost is significantly higher; (3) softened, RO-treated water at a whole-house level can be aggressive toward copper pipes. For most residential customers, we recommend a whole-house filtration system for overall water quality improvement and a point-of-use RO system under the kitchen sink for drinking and cooking water — this combination achieves the best results at the best cost.

A standard under-sink RO installation takes 2–3 hours. We shut off the cold water supply under your sink, install a feed water saddle valve, run color-coded supply tubing to the RO head assembly (mounted inside the cabinet), run a drain line to your sink drain, connect the storage tank, and install the dedicated RO faucet through your sink's available faucet hole (or drill one if needed). We then flush the system, take a TDS reading before and after, and walk you through filter change schedules. Your kitchen is functional the same day.