Maintain whole-house RO pretreatment against the requirements of the installed membrane, pump and prefilter assembly. Do not use a universal 10–15 PSI change rule or a generic chlorine strip as the entire maintenance plan.

Create a stage-specific service card

Stage or requirement Record from the system documents Measurement or action
Sediment protection Approved cartridge and maximum permitted restriction Inlet/outlet readings at a repeatable operating flow
Disinfectant protection Membrane tolerance and specified pretreatment The required test method, range and sampling point
Pump supply Permitted inlet conditions and protection controls Confirm normal feed conditions; investigate alarms
Scale or metal control Source-water limits and pretreatment design Water analysis and the specified maintenance routine
Restart Isolation, flushing, sanitation and commissioning steps Follow the assembled system’s documented procedure

For a combined filter bank, gauges at its ends show total bank loss. They do not identify which cartridge is responsible. Label the measurement points so a later service visit compares the same section.

Separate restriction from chemical protection

A clean-looking cartridge can be restrictive, while freely flowing carbon may no longer meet its treatment duty. Pressure readings and a disinfectant test answer different questions. A TDS meter does not establish carbon’s remaining disinfectant-reduction capacity.

Confirm whether the supply uses free chlorine, chloramine or another disinfectant with the supplier and system designer. The test method must resolve the membrane’s specified requirement. A result below a coarse test strip’s reporting range is not proof that a more demanding limit has been met.

DuPont’s FilmTec technical manual illustrates why pretreatment and commissioning are tied to membrane-feed specifications. It is not permission to apply FilmTec procedures or limits to an unidentified residential system.

Make before-and-after readings comparable

Record the date, operating state, approximate feed flow, inlet and outlet pressures, exact cartridge parts and relevant test results. Compare with the documented clean-system record under similar conditions. A larger pressure difference at a much higher flow does not by itself prove that a cartridge has loaded.

For example, 48 PSI before a bank and 44 PSI after it gives a 4 PSI difference. After service, compare another 4 PSI reading only if the operating flow is comparable. The calculation is simple subtraction; whether it is acceptable comes from the equipment limits and available pressure margin.

Treat service and restart as separate jobs

Have the qualified service provider follow the system’s shutdown, pressure-relief, electrical-isolation and hygiene procedure. Use only approved replacement parts, cleaning products and lubricants. Do not invent a sanitizer concentration or open a pressurized housing.

Before returning the membrane to service, complete the specified cartridge flushing and verify that feed conditions meet the documented requirements. A replaced cartridge is not a completed service if flushing, leak checks or the required water-quality checks remain undone. Keep the bypass state and any untreated-water exposure in the service record.

Investigate an unusually short service interval

Repeated loading can indicate changed source water, an unsuitable cartridge, inadequate pretreatment or another system fault. Do not automatically install a coarser cartridge or increase pump pressure: either can defeat the original protection design.

Use the well-water panel guide for changed source conditions and the pressure-loss guide for hydraulic evidence. If only drinking and cooking water needs RO, the whole-house versus under-sink comparison helps reassess scope before a major replacement.

This guide provides a service-record framework. It does not replace commissioning instructions, specify treatment doses or certify an RO installation.

Record each prefilter in the stage-by-stage maintenance register .