RO Troubleshooting: Find Your Symptom, Fix the Problem

Continuous Water Running to Drain (Won't Stop)

Test: Turn OFF the electrical wall power to the purifier. Observe the reject drain tube for 3 minutes. Does water STILL flow to drain?

Expected: Water to drain must completely cease within 30–60 seconds of switching off electrical power.

Reading: If water continues flowing to drain with power OFF, the 24V Solenoid Valve is mechanically jammed open with silt or its internal rubber seal is degraded. Pressurized raw feed water bypasses directly to drain 24/7.

Replace the 24V Solenoid Valve. Ensure copper coil rating matches your SMPS output (24V or 36V).

Test: Allow purifier to fill tank until pump stops. Close the storage tank ball valve. Wait 2 minutes, then gently open tank valve. Does pump start immediately or reject water discharge?

Expected: Check valve on pure permeate port must prevent stored tank water from backflowing into the membrane housing.

Reading: A worn or scale-jammed NRV lets pressurized water inside the storage tank leak back through the membrane into the reject line, continuously dropping tank pressure and triggering pump to run non-stop.

Unscrew the 1/4" check valve fitting from the pure water permeate port of the membrane housing and install a new brass/POM NRV.

Test: With storage tank full and pump still humming, disconnect one electrical terminal spade connector from the HPS.

Expected: Booster pump and solenoid valve must immediately cut off.

Reading: If tank is completely full and pressurized, the HPS internal micro-switch diaphragm has seized closed or lost spring tension, never opening electrical contacts to signal shutdown.

Replace the High-Pressure Switch. Ensure it is plumbed on the pure water line between check valve and storage tank.

Test: Lift the storage tank. Is it abnormally heavy (12–15 kg) yet delivers only a weak 1-liter trickle before stopping? Depress the Schrader tire-valve pin on tank side/bottom.

Expected: Dry air should hiss out at 6–8 PSI. If liquid water squirts out of the air valve, the internal butyl rubber diaphragm has burst.

Reading: A waterlogged tank has zero air cushion to build 40 PSI back-pressure. Without back-pressure, the HPS never trips and the system runs continuously.

Replace the storage tank. Air bladder cannot be repaired once ruptured.

Test: Measure pure water output rate into a measuring cup. A 75 GPD membrane should deliver 200–250 mL/min.

Expected: Booster pump must generate 80+ PSI running pressure to build 40 PSI in storage tank.

Reading: A worn booster pump with hardened diaphragms can only generate 30–40 PSI total. It produces slow water but cannot overcome the HPS cutoff threshold, keeping the motor running indefinitely.

First test SMPS adapter with multimeter (must maintain 24V under pump load). If SMPS is healthy, replace booster pump.

Test: In cabinet purifiers with transparent tanks, lift the float arm manually with your finger.

Expected: Lifting the float must instantly cut power to pump and SV within 1 second.

Reading: If lifting float does not stop purifier, float micro-switch is oxidized/shorted or float arm is mechanically jammed with calcium scale.

Replace the float switch assembly. Clean scale around tank hinge bracket.

No Water Coming Out at All (Completely Dry)

Test: Disconnect the 1/4" or 3/8" white inlet tube from pre-filter housing and point it into a bucket.

Expected: Continuous strong stream of tap water should discharge with good force.

Reading: No water from raw inlet tube means building overhead tank is empty, main plumbing valve is off, or diverter valve is choked with pipe rust.

Open raw water inlet valve fully. Check building water supply. Remove rust debris from inlet tap mesh.

Test: Check if the green/blue LED indicator on SMPS power adapter is glowing. Measure output voltage at adapter DC plug.

Expected: DC voltmeter must measure steady 24.0V–24.5V DC (or 36.0V for 36V models).

Reading: No LED or zero voltage indicates blown internal fuse, thermal burnout, or voltage spike failure. Pump and solenoid receive zero electricity.

Replace SMPS adapter with high-efficiency 24V 2.5A or 3A unit with copper transformer winding.

Test: Temporarily bridge the two wire terminals of the LPS using an insulated screwdriver or jumper wire for 5 seconds.

Expected: If machine instantly turns ON when bridged, the LPS is functioning correctly to protect pump from dry-run.

Reading: Incoming line pressure is below 5 PSI (common when supply comes from low-height overhead tank). Booster pump cannot run without water.

Ensure inlet line is directly connected to overhead tank. If supply pressure is naturally weak (<4 PSI), adjust LPS calibration screw or add a gravity feed boost.

Test: Turn on power. Feel the solenoid valve body. Does it make a crisp 'click' sound when power is applied?

Expected: Solenoid should click sharply and feel slightly warm during operation. Water should flow freely past SV output.

Reading: No click and zero water passing through SV means solenoid electrical coil is open-circuited. Raw water cannot enter booster pump.

Replace the 24V solenoid valve.

Test: Verify 24V DC reaches pump wire terminals with multimeter while machine is powered on.

Expected: Pump should vibrate strongly and hum smoothly.

Reading: 24V present at pump terminals but zero motor vibration or humming means motor armature or thermal fuse is burnt out.

Replace the booster pump. Ensure SMPS matches pump wattage.

Very Slow Water Flow (Drop-by-Drop Trickle)

Test: Inspect the 10-inch transparent housing bowl. Has the white spun cartridge turned dark brown/black? Disconnect tube after pre-filter.

Expected: Water should shoot out with good line pressure after the pre-filter.

Reading: If water merely trickles after the pre-filter, the spun cartridge is choked with mud. This is the #1 most common issue in Indian households.

Replace with genuine 150g heavy PP spun filter. Costs under ₹70 and takes 5 minutes to DIY.

Test: For purifiers with external pressure tank: is the tank heavy (full of water), but flow stops after 1–2 glasses?

Expected: Tank should push out 8 liters of water at constant high velocity until nearly empty.

Reading: Air bladder pressure has dropped from 7 PSI to 0 PSI. Water is trapped in tank because there is no air cushion pushing it up to the faucet.

Empty the tank completely through faucet. Attach bicycle pump with pressure gauge to tank Schrader valve; pump up to exactly 7–8 PSI empty.

Test: Disconnect the inlet and outlet tubes of the inline post-carbon filter. Blow through it or test water flow.

Expected: Water should flow with minimal restriction through fresh inline filters.

Reading: Fine carbon silt or calcium scales have compacted inside the filter cartridge, strangling flow.

Replace inline sediment and post-carbon filters. Flush carbon filter for 2 minutes before connecting to membrane.

Test: Disconnect the pure water permeate tube directly from the membrane housing outlet with pump running.

Expected: Should deliver steady stream of 200–250 mL per minute (for 75 GPD membrane).

Reading: If pump pressure is healthy (>70 PSI) and pre-filters are new, but permeate tube produces only a slow drip, membrane pores are encrusted with silica/calcium scale.

Replace RO membrane. Always replace the flow restrictor (FR 450) simultaneously.

High TDS in Output Water (Salty / Hard Water Taste)

Test: Measure Raw Feed TDS and Pure Output TDS with digital meter. Calculate Rejection: [(Raw - Pure) / Raw] × 100.

Expected: TDS rejection rate must be 90% to 96%. E.g., 1000 ppm raw water should yield 40–90 ppm pure water.

Reading: If rejection rate is below 80% (e.g., 1000 raw yields 300+ pure), the membrane polyamide barrier is ruptured or chemically burnt by chlorine.

Replace RO membrane. Also replace carbon pre-filter to prevent fresh membrane from chlorine damage.

Test: Locate the brass/plastic needle valve connected between pre-filter and post-carbon (TDS adjuster). Turn screw fully clockwise (closed).

Expected: Output TDS should plummet to pure RO base level (20–50 ppm) within 3 minutes of closing bypass.

Reading: TDS controller was opened excessively, allowing unpurified raw water to flood into the pure drinking stream.

Calibrate TDS controller: Turn fully clockwise to close. Then open by 1/8 turn increments while checking TDS until output reads 80–120 ppm.

Test: Check the FR rating on the black/white drain tube. Is it marked FR 450 (for 75 GPD) or FR 550 (for 100 GPD)?

Expected: FR creates the necessary osmotic back-pressure for salts to be rejected into the drain stream.

Reading: An oversized FR (e.g., FR 800 on 75 GPD membrane) drops housing pressure, cutting TDS rejection efficiency drastically.

Install correct FR matching membrane capacity (75 GPD = FR 450; 100 GPD = FR 550).

Test: Open membrane housing cap. Pull out membrane. Inspect the two small rubber O-rings on the center product stem.

Expected: Both O-rings must be intact, pliable, and seated securely in grooves.

Reading: Nicked, twisted, or missing O-rings let pressurized raw brine bypass directly into the pure water collection tube.

Lubricate O-rings with food-grade silicone grease and reseat. Replace membrane housing if internal stem socket is cracked.

Bad Taste, Odor or Chemical Smell in Purified Water

Test: Taste water directly from the membrane pure tube vs tasting water dispensed from the storage tank faucet.

Expected: Water fresh from membrane should taste neutral and crisp.

Reading: If membrane water tastes fresh but tank water smells musty, bacterial biofilm or slime has developed on internal tank walls.

Sanitize tank: Dissolve 1 tablespoon food-grade hydrogen peroxide or 5 drops unscented sodium hypochlorite in 2 liters water; circulate through tank, drain, and rinse twice.

Test: Check service age of inline post-carbon filter. Has it been installed longer than 12 months?

Expected: Fresh activated carbon absorbs trace organics and VOCs, providing a sweet natural taste.

Reading: Exhausted carbon loses adsorption capacity and starts releasing desorbed organic molecules, causing stale or sour taste.

Replace with high-iodine (1100+ IV) coconut shell inline carbon filter.

Test: Test water pH with test strips. Pure RO without mineralizer is naturally acidic (pH 5.8–6.3), which tastes flat or bitter.

Expected: Quality alkaline cartridge balances pH to 7.4–8.0 with smooth, pleasant mouthfeel.

Reading: Cheap duplicate mineral cartridges release chalky white powder or bitter mineral salts.

Install genuine Biocera or certified food-grade alkaline cartridge with natural mineral beads.

Loud Motor Noise, Rattling or Heavy Vibration

Test: Open faucet and loosen the pre-filter housing slightly until water squirts, purging trapped air bubbles.

Expected: Noise drops to smooth quiet hum within 3–5 minutes once air clears.

Reading: Trapped air causes severe hydraulic cavitation in pump diaphragm chambers, producing loud sputtering and knocking.

Purge air: Run machine with faucet open for 5 minutes. Tap filter housings gently to release lodged bubbles.

Test: Place your hand on pump body. Does it generate severe high-frequency vibration or screeching metallic friction?

Expected: Normal pump emits smooth low hum under 55 dB.

Reading: Water seepage through internal diaphragm seal into motor ball bearings causes bearing seizure, rust, and loud screeching noise.

Replace pump or install new diaphragm pump head if motor armature is undamaged.

Test: Press cabinet firmly against wall with your palms while machine runs.

Expected: If noise drops substantially when pressed, vibration is resonating through wall mounting plate.

Reading: Loose wall screws or missing rubber damping pads magnify normal motor rotation into loud cabinet buzzing.

Tighten mounting screws and place rubber grommets or high-density foam behind purifier corners.

Water Leaking Underneath Purifier (Flooding Risk)

Test: Dab dry tissue paper around each push-fit elbow and union. Where does tissue get wet first?

Expected: Joint must remain bone dry under 100 PSI pressure.

Reading: Tube end was cut with scissors at an angle (causing oval sealing) or stainless steel locking teeth scratched the tube outer surface.

Cut tube end cleanly square (90° angle) with razor blade. Push firmly into fitting until it passes O-ring (15 mm depth). Insert blue locking clip.

Test: Inspect the thread perimeter of the 10-inch housing bowl while purifier is operating.

Expected: Water should not weep or drip from thread seam.

Reading: Rubber O-ring got twisted during hand-tightening, pinched, or dried out without silicone lubrication.

Unscrew housing with spanner. Clean O-ring groove, coat O-ring with food-grade silicone grease, and re-tighten firmly.

Test: Inspect bottom weep-hole between pump motor housing and plastic pump head.

Expected: Motor casing must be completely dry.

Reading: Pump diaphragm seal has failed, allowing pressurized water to enter motor front plate and drip out of motor vent.

Immediately disconnect power to prevent motor short-circuit. Replace booster pump or pump head assembly.