The APEC ROES-50 is a 5-stage under-sink reverse osmosis system used for drinking water, typically installed in kitchens for improved taste and contaminant reduction. Many "failures" are actually scheduled maintenance events: clogged pre-filters, an exhausted RO membrane, or a low-pressure storage tank.
Repairs are usually economical because replacement filters and membranes are relatively inexpensive compared with the unit cost, and the system's value is in ongoing filtration rather than electronics. Replacement becomes more attractive when the housing cracks, fittings leak repeatedly, or the tank or shutoff valve failures become chronic and cause water damage risk.
Use the threshold to decide if you're stacking multiple parts at once; if a tank, membrane, and valves all need replacement together, a new system with fresh warranty may be simpler. Also check incoming water pressure; low pressure can mimic poor RO performance and cause premature wear.