Reverse Osmosis System Installation SOP

Purpose

Standardize installation of residential RO systems (kitchen drinking-water grade). Quality install determines years of trouble-free pure water; cut corners create leaks + low pressure.

Scope

Under-sink point-of-use (POU) RO systems. Excludes whole-house RO, commercial systems.

Prerequisites

• RO system (3-5 stage typical)
• Tools: drill, hole saw, wrench, tubing cutter
• Standard install kit (faucet, fitting, drain saddle)
• 2-3 hours per installation
• Cold water supply + drain accessible under sink
• Sometimes second hole in countertop needed for faucet

Procedure

Step 1: Site assessment

1. Verify cold water supply under sink (RO needs cold only)
2. Check supply pressure (40-100 PSI optimal; needs boost above 65 PSI for some membranes)
3. Locate space for RO unit (typically under-sink)
4. Verify drain accessibility for saddle
5. Verify counter space for faucet (or existing faucet hole)

Step 2: Shut off water + drain

1. Close cold water valve under sink
2. Open existing faucet to relieve pressure
3. Have towel/bucket for residual water

Step 3: Mount RO unit

1. Mount unit to side wall of cabinet
2. Use provided brackets
3. Level + secure
4. Allow access to filter housings for future change

Step 4: Install faucet

1. If hole exists: position faucet, tighten from below
2. If new hole: drill in countertop (1-1/4" hole typical)
3. Connect supply tubing to faucet

Step 5: Connect to cold supply

1. Use saddle valve (tap into existing supply) OR T-fitting
2. T-fitting preferred (better reliability)
3. Connect supply tubing to RO inlet

Step 6: Connect drain

1. Install drain saddle on drain line
2. Drill access hole
3. Connect drain tubing from RO to drain saddle
4. Maintain air gap (some jurisdictions require)

Step 7: Install tubing + tank

1. Connect tank to RO output (storage tank holds pressurized water)
2. Tank stands upright; air-pressurized

Step 8: Flush + test

1. Open cold water supply
2. Allow RO to flush for 1-2 hours (clears membrane preservative)
3. Drain initial water (some manufacturers specify 2 tank-fills)
4. Final water test: TDS meter shows reduced TDS (typical 90-95% reduction)

Step 9: Customer briefing

1. Show faucet operation
2. Explain tank refill time (slow; 1-2 hours after major use)
3. Filter replacement schedule (varies by stage):
   • Pre-filter: every 6 months
   • Carbon filter: every 6-12 months
   • Membrane: every 2-3 years
4. Tank pressure check (annual)
5. Provide manuals + log

Acceptance criteria

• All connections leak-free
• TDS test shows 90-95% reduction
• Water flow at faucet (slow but steady)
• Customer signoff

Common pitfalls

• Saddle valve corrosion: cheap saddles fail; prefer T-fitting
• Drain saddle improper: leaks under sink
• Wrong tubing connections: kinks restrict flow
• No air gap on drain: code violation in some jurisdictions
• Tank pressure low: slow refill (pressurize 7-10 PSI when empty)
• Membrane not flushed: chlorine + preservative in first water

TDS reduction expectations

If TDS reduction < 80%, troubleshoot.

Service intervals

References

• WQA RO standards
• Manufacturer installation manuals
• NSF 58 (RO certification standard)
• Manuall internal: How to Balance Pool Water Chemistry, Water Filtration Technologies Reference