RO Plant for Housing Society — Cost, Capacity & Setup Guide (2026)

Size on drinking and cooking water only. Bathing, flushing and laundry should continue on the society's normal supply — treating all of it through RO would multiply your capex and reject volume for no benefit.

• Estimate 4-5 litres per resident per day for drinking and cooking.
• A 60-flat society at 3.5 residents per flat needs roughly 900-1,050 litres a day.
• Divide by realistic running hours (8-10, not 24) to get LPH — about 100-130 LPH in that example, then size up one step for peak draw and future occupancy.
• Add storage of at least one day's demand so a plant fault does not become an immediate crisis.

A common tap point is cheaper and simpler, and works where the society is willing to absorb water cost into maintenance charges. A card or RFID-operated water ATM meters consumption per flat, which resolves the most common objection raised in general body meetings — that low-consumption households are subsidising high-consumption ones.

Water ATMs add roughly ₹60,000-1,50,000 depending on the number of dispensing points and whether you want prepaid card, RFID or app-based metering. For societies above about 80 flats, the reduction in disputes usually justifies it.

This is usually the harder half of the project. What committees consistently ask for, and what you should have ready before the general body meeting:

• A lab water analysis report showing why the plant is needed, with the TDS or contaminant numbers stated plainly.
• Per-litre cost comparison against individual purifiers and against packaged water cans.
• Total five-year cost including power, AMC, consumables and operator time — not just the capex figure.
• Space, drainage and electrical load requirements confirmed with the society's own contractor.
• The reject-water plan, since 30-50% of feed water leaves as reject and committees will ask where it goes. Landscaping and flushing reuse are the usual answers.

Commercial and industrial systems are engineered as a treatment train, not a single appliance. Each module protects the one after it, and skipping a stage to save capex is the most common reason plants fail early.

• Pre-treatment module — multigrade sand filter removes suspended solids and turbidity; activated carbon filter strips chlorine and organics that would oxidise the RO membrane.
• Softening or antiscalant dosing — protects membranes from calcium and magnesium scaling. On hard feed water this is not optional.
• High-pressure RO module — heavy-duty booster pump drives feed water through industrial spiral-wound membranes at 12-18 bar.
• Post-treatment disinfection — UV disinfection and/or ozonation, with mineral dosing where potable taste matters.
• Microprocessor / PLC control — auto start-stop on tank level, dry-run protection, low and high pressure cut-offs, and timed membrane flushing to extend membrane life.

Capital cost is usually 30-40% of what a commercial water system costs you over five years. The rest is power, membrane and cartridge replacement, reject water, and labour. Two plants with identical price tags can differ by 60% in five-year TCO.

• Power — energy-efficient pumps and correctly sized motors are the largest controllable operating cost on plants above 500 LPH.
• Recovery ratio — a plant recovering 70% instead of 45% cuts both your feed water bill and your reject disposal volume substantially.
• Membrane life — driven almost entirely by pre-treatment quality and flushing discipline, not by membrane brand.
• Consumables — cartridge filters, antiscalant and salt for softener regeneration, budgeted monthly rather than as surprises.
• AMC and downtime — for a production facility, unplanned downtime usually dwarfs every other line item.

Commercial buyers are buying uptime, so the commercial terms matter as much as the equipment specification. Insist on these being written into the purchase order rather than discussed verbally.

• Site survey and feed-water analysis before the final quotation — never accept a specification produced without a water report.
• Defined commissioning scope: civil and electrical prerequisites, who supplies what, and a documented performance test at handover.
• Written service response times, with escalation, and clarity on whether spares are held locally.
• Operator training and a laminated SOP left on site, so routine flushing and cartridge changes do not depend on one person.
• Warranty terms stated separately for membranes, pumps, vessels and instrumentation, because they differ.