Pure Water Machine Common Faults: 11 Problems and Solutions for RO Water Purifier Troubleshooting 2026

Pure water machines used in homes and offices can develop various faults over time — from pump failure and water leakage to abnormal noise and unbalanced water ratios. Understanding pure water machine common faults and their solutions helps users quickly diagnose issues and reduce downtime. This guide covers 11 pure water machine common faults for reverse osmosis water purifiers, with detailed troubleshooting steps for each problem. Whether the high-pressure pump will not start, the machine keeps flushing, or the pure water flow is insufficient, the following diagnostic procedures will help you identify and resolve the issue.

Pure Water Machine Common Faults: Quick Overview

Fault 1: High-Pressure Pump Does Not Start and Cannot Make Water

Possible causes and checks:

• Check whether there is a power failure and whether the plug is plugged in properly
• Check whether the low-voltage switch is out of order and cannot connect to the power
• Check whether the high-pressure switch or water level controller fails and cannot be reset
• Check whether the transformer and fuse are burnt — if the fuse is blown, replace it

Fault 2: High-Pressure Pump Works Normally But Cannot Make Water

Possible causes:

• Loss of pressure in high-pressure pump — the pump may have worn seals or damaged internal components. Send for repair.
• Pre-filter is blocked — if there is no pure water or waste water, or the waste water flow is very small, the pre-filter elements (PP, GAC) may be fully clogged. Replace filter elements.
• Check valve is blocked — waste water present but no pure water. Replace check valve.
• Inlet solenoid valve fails — valve cannot open effectively, preventing water from entering the system. Replace solenoid valve.
• RO membrane is blocked — complete membrane fouling preventing permeate production. Replace RO membrane.

Fault 3: High-Pressure Pump Does Not Stop

Possible causes:

• Insufficient pump pressure — the pump cannot reach the set pressure to trigger the high-pressure switch. Check pump performance.
• Check valve is blocked — pure water does not come out (waste water present but no pure water). Replace check valve.
• High-voltage switch fails — switch cannot detect pressure and disengage. Replace high-voltage switch.
• Solenoid valve fails — cannot open effectively. Replace solenoid valve.

Fault 4: High-Pressure Pump Stops But Waste Water Does Not Stop

Possible causes:

• Solenoid valve failure: The valve cannot effectively cut off water flow. Inspection method: close the pressure tank ball valve. If waste water continues flowing, the solenoid valve is faulty. Replace it.
• Water pressure too high: Close the inlet solenoid valve and reopen. If the machine operates normally after this, the incoming water pressure is too high, forcing the solenoid valve open. Install a pressure regulator.

Fault 5: Machine Jumps Repeatedly After Water Is Full

Possible causes:

• Insufficient raw water pressure — low feed pressure causes the low-pressure switch to cycle. Check and boost water pressure.
• Check valve pressure relief — water flows backward through a leaking check valve. Replace the check valve.
• High-voltage switch failure — switch cannot hold the shut-off signal. Replace switch.
• System pressure relief — check all connections and components for pressure leaks. Reconnect or replace leaking parts.

Fault 6: Pressure Tank Is Full But Pure Water Cannot Flow Out

Possible causes:

• Pressure barrel air pressure low — the air charge in the tank bladder has been depleted. Re-inflate to approximately 7 psi. Check for air leaks; replace the tank if it cannot hold pressure.
• Rear activated carbon block — the post-carbon filter is clogged, restricting flow. Replace the post-filter element.
• Pressure barrel ball valve damaged — the valve may be stuck or broken. Inspect and replace if needed.

Fault 7: Insufficient Pure Water Flow

Possible causes:

• Pre-filter is blocked — PP, GAC, or CTO filter elements may be clogged with sediment or organic matter. Replace all pre-filter elements.
• Insufficient high-pressure pump pressure — pump wear reduces output pressure. Send pump for repair or replacement.
• RO membrane clogging — membrane fouling reduces permeate production. Replace RO membrane.
• Waste water ratio imbalance or flush switch not closing tightly — excessive water goes to waste instead of permeate. Adjust or repair the flow restrictor.

Fault 8: Pure Water to Waste Water Ratio Is Seriously Out of Balance

Possible causes:

• Flush solenoid valve damage — the valve may be stuck partially open, allowing excessive water to bypass the membrane. Replace the flush solenoid valve.
• Waste water restrictor blocked or too conductive — the flow restrictor may be clogged or worn, altering the ratio. Clean or replace the restrictor.
• RO membrane blocked or removal rate severely reduced — a damaged membrane reduces permeate production, changing the ratio. Replace the RO membrane.

Fault 9: Machine Keeps Flushing

Possible causes:

• Waste water ratio valve failure — if the valve is stuck or damaged, the system may remain in flush mode. Inspect and replace the valve.
• Flush valve not closing tightly at startup — the flush solenoid may not be fully seating. Check valve operation; clean or replace as needed.

Fault 10: Loud Noise During Operation

Possible causes:

• Raw water pipeline cut off — if the water supply is interrupted, the booster pump runs dry, producing loud noise and risking pump damage. Restore water supply and check the feed line.
• Air in the water supply — for water supply without a tower, air may be entrained in the feed water, causing pump cavitation noise. Install an air release valve.
• Booster pump failure — worn bearings, excessive vibration, or friction sounds indicate pump malfunction. Send pump for repair.
• Loose components — check if the water purifier casing or internal brackets are vibrating against surfaces. Tighten loose parts.

Fault 11: Water Leakage

Possible causes:

• Check the water circuit of the water purifier — inspect all tubing connections and find the leaking point. Tighten or replace fittings as needed.
• Check quick-connect fittings — if Xiao Unicom (John Guest style) fittings are leaking, the O-ring may be damaged or the tube may not be fully inserted. Re-seat or replace fittings.
• Check the water dispenser connections — if the unit includes a dispenser, inspect dispenser lines for leaks.
• For very small leaks — use a dry tissue test to trace the leak path. Even pinhole leaks will show on tissue over time.

Frequently Asked Questions

Q1: How often should pure water machine filters be replaced?

PP sediment filter every 3-6 months, granular activated carbon every 6-12 months, carbon block every 6-12 months, RO membrane every 2-3 years, and post-carbon filter every 12 months. These intervals depend on feed water quality and daily water consumption.

Q2: What is the normal pure water to waste water ratio for RO systems?

A healthy RO system produces a 1:2 to 1:3 ratio (1 part pure water to 2-3 parts waste water). If the ratio shifts significantly (e.g., 1:5 or more), check the flow restrictor, flush valve, and RO membrane condition.

Q3: Why does my pure water machine make a clicking sound?

Clicking sounds usually come from the solenoid valves or the high-pressure switch cycling on and off. If the clicking is frequent, it may indicate pressure tank air loss, a leaking check valve, or incorrect switch settings.

Q4: Can I install a pure water machine myself?

Basic installation is possible for DIY users with plumbing experience. However, if you encounter repeated post-installation faults (such as continuously running waste water or low flow), professional installation is recommended to ensure proper setup of the check valve, flow restrictor, and pressure tank.

Q5: How do I sanitize my pure water machine?

Annual sanitization is recommended. Remove all filter elements and RO membrane, fill the housing with a 50-100 ppm chlorine solution or food-grade hydrogen peroxide, circulate for 15-20 minutes, then flush thoroughly with clean water before reinstalling filters.

Conclusion and Call to Action

This guide has covered 11 pure water machine common faults — from pump starting issues and water flow problems to noise and leakage. Regular filter replacement and prompt attention to warning signs will extend the life of your RO pure water machine and maintain consistent water quality.

CHIWATEC Water Treatment Technology is a high-tech enterprise specialized in water processing devices. We provide RO system parts, maintenance support, and technical assistance. For troubleshooting help, email [email protected] or [email protected] with your system model and fault description.

Related Resources and Further Reading

• RO Pure Water Machine: Complete Guide — Selection and installation guide for home RO systems
• RO Pure Water Machine Usage Guide — Operation and maintenance instructions
• RO Pure Water Equipment Complete Guide — Comprehensive RO system overview
• Pollution Control for RO Systems — Membrane fouling prevention strategies
• Chiwatec RO Water Treatment Systems — Browse RO equipment