Water plant maintenance — a practical schedule

Short answer: Most plant failures are preventable and follow from a handful of skipped routine tasks. A daily check takes five minutes, a weekly record takes ten, and together they prevent nearly every expensive failure we see.

The schedule below covers a typical RO plant with softener and dosing.

Daily — five minutes

• Check dosing tank levels — antiscalant and SMBS. Are they falling?
• Glance at pressure gauges — any sudden change?
• Check permeate TDS
• Check hardness after softener — with a test kit
• Look for leaks around housings and fittings
• Listen to the pumps — any change in sound

Weekly — ten minutes

Record these six numbers:

1. Permeate flow (LPH)
2. Reject flow (LPH)
3. Feed pressure
4. Pressure after cartridge (so you have ΔP)
5. Feed TDS
6. Permeate TDS

From these you can calculate recovery and rejection, which tell you the plant's health. See our monitoring guide.

Also weekly: check the brine tank salt level and look for bridging.

Monthly

• Calibrate sensors — pH, ORP and conductivity. See our calibration guide
• Verify dosing pump output — measure into a jar for a set time
• Backwash media filters if not automatic
• Clean the brine tank if sludge is visible
• Check O-rings on housings
• Review the weekly records for trends

Quarterly

• Change cartridge filters — or sooner if ΔP dictates
• Inspect and clean sensors
• Check pump performance against rated pressure and current
• Test SDI on the feed water
• Check electrical connections in the panel

Annually

• CIP cleaning of membranes, or sooner if performance dictates
• Full water analysis — the source may have changed
• Replace pH sensors — they typically last 12 to 18 months
• Clean brine tank thoroughly
• Inspect vessel internals if performance suggests a problem
• Check media condition — resin lasts 4 to 7 years, carbon 1 to 3
• Service pumps

Spares worth holding

The pH sensor is the one people regret not holding. On an ETP or a controlled process, a failed sensor stops proper operation and replacements take days.

The record book

Keep one book at the plant with:

• Baseline readings from when the plant and membranes were new
• Weekly readings
• Cartridge change dates and the ΔP at change
• Calibration dates and values
• Chemical consumption
• Any faults and what was done

Where plants actually fail

Ranked by how often we see them:

1. Dosing tank ran empty — not noticed for weeks
2. Cartridge changed too late — no gauges fitted
3. Softener stopped working — brine problem, not noticed
4. Sensor never calibrated — decisions made on wrong readings
5. Membrane cleaned too late — fouling became irreversible
6. Chlorine reaching membrane — no dechlorination or it failed

Every one of these is prevented by the daily and weekly checks above.

Training the operator

Whoever runs the plant should know:

• What each reading should be, and what to do if it is not
• How to change a cartridge and check the O-ring
• How to make up dosing solution correctly
• How to calibrate the sensors
• How to regenerate the softener, if manual
• When to call for help rather than adjusting things

That last point matters. Most of the serious damage we see comes from someone adjusting the reject valve or increasing a chemical dose to "fix" a symptom, rather than diagnosing the cause.

Frequently asked questions