Start with the kitchen.
If drinking and cooking water are your main priorities, a point-of-use system may fit the conversation better than treatment for every tap. Discuss how you use the kitchen sink, whether you fill large bottles, and whether a refrigerator connection is part of the request.
An under-sink RO system can be quoted on its own or together with whole-home filtration. The proposal should make clear which equipment treats the home and which equipment serves the drinking-water faucet.
Know how reverse osmosis fits.
Reverse osmosis uses a membrane as part of a treatment process. Point-of-use RO systems produce a reject-water stream, so compare water efficiency along with rated output and replacement expenses. EPA’s WaterSense program offers information on efficiency and verified performance.
Make room for the details
- Available space under the sink, including disposal and storage.
- Faucet style, an existing accessory hole, and any drilling requirements.
- Tank or tankless configuration and any power requirement.
- Installation and drain connection requirements for the selected model.
- Filter and membrane replacement part numbers and costs.
Specific concerns need specific documentation.
If you are considering treatment for a particular substance, ask for the selected model’s certification and performance data for that substance. A system type or a broad “purifier” label is not enough to establish what your installation will do.
Compare more than a stage count.
Tank and tankless models have different space, output, power, and replacement-filter requirements. Remineralization is an optional feature to discuss for taste preferences; it is not present in every RO system. Request the exact model and maintenance costs instead of choosing by the number of stages alone.