What happens on install day
- Water off. The installer shuts off the supply, so plan for a stretch without water.
- Plumbing connection. Under-sink systems tap the cold line; whole-home systems connect to the main line, usually with a bypass valve.
- Drain and power. RO systems need a drain connection under the sink; backwashing filters and softeners need a drain line and often an outlet.
- Startup. Media is flushed, the softener is programmed, and the RO tank fills and is flushed per the manual.
- Walkthrough. You should be shown the bypass, the schedule, and what to watch for.
What makes it take longer
- The main line is hard to reach or made of a material that needs extra fittings.
- No drain or outlet near the install spot.
- A countertop that needs a new hole for the RO faucet (stone takes more care).
- Combining a filter and a softener, or adding pre-filtration.
- Fixing existing issues found on site, such as a failing shutoff valve.
- Building or HOA approvals in condos and some communities.
Before install day: test and plan
The longest step is often the one before installation: testing the water and choosing the right setup. The EPA's WaterSense guide recommends setting treatment goals from your water report and test results first. With Living Water, that starts with Jorge's free in-home test, followed by a recommendation and an itemized quote. See what happens during a home water assessment.
After install: the first days
Expect some normal startup behavior: air spurting from faucets, a short period of cloudy water that clears, and an RO tank that takes time to fill the first time. A softener may need a few days of use before you notice a change in spotting. If water stays discolored or a fitting drips, call the installer.
Under-sink RO vs whole-home: a quick comparison
| Under-sink RO | Whole-home filter or softener | |
|---|---|---|
| Where it connects | Cold line under the kitchen sink | Main water line where water enters |
| Drain needed | Yes, at the sink drain | Yes, for backwashing or regenerating models |
| Power needed | Usually not; some models have pumps or electronics | Often, for the control valve |
| Main time factors | Countertop hole, cabinet space | Line access, drain run, bypass, startup and programming |
If you are installing both, they are often done the same visit, with the whole-home system first. Read the comparison of whole-house filtration vs reverse osmosis to see how they work together.
How to prepare
- Clear the cabinet under the sink, or the area by the main line.
- Know where your main shutoff is.
- Tell the installer about any planned remodeling.
- If you rent or live in a condo, get approval first. See the rental approval checklist.
https://www.epa.gov/system/files/documents/2025-01/ws-products-home-water-treatment-guide_v2_508.pdf
https://www.epa.gov/watersense/point-use-reverse-osmosis-systems
Updated 2026-10-17 · Living Waters · Jorge Canela, Water Quality Specialist