Pentair Merlin RO is an on-demand point-of-use reverse-osmosis system with a sediment/carbon prefilter, two RO elements in series, and a carbon postfilter. Merlin I documentation lists tankless operation and a 2,831 L/day certified production rating. Actual output, unit condition, replacement parts, and availability must be verified before purchase.
PT Watermart Perkasa, operating through water.co.id, helps Indonesian buyers assess installed Pentair Merlin systems, consumables, and replacement options. For a new project, compare the Merlin data with the Pentair ES60-S under-sink RO system, a current Watermart offering with a nominal 600 GPD class and 1.5 L/min pure-water flow.
Updated 30 July 2026: Merlin I data was separated from the current ES60-S option, and performance claims were returned to their documented test conditions.
What Is the Pentair Merlin RO System?
Merlin I is an on-demand RO system for one drinking-water outlet. The 2010 Pentair PRF-RO/Merlin brochure describes four treatment stages: a carbon prefilter, two RO elements operating in series, and a carbon postfilter. The documented arrangement uses inlet-water pressure and does not require a pump or storage tank under its stated conditions.
That older document is useful for identifying an installed system; it does not prove that every model, cartridge, or part number remains available. Send photographs of the system and component labels before treating a replacement part as compatible.
| Listed component | Documented part number | What to verify |
|---|---|---|
| Merlin I complete system | 1205052 | Unit identity, revision, connections, and installed condition |
| 5-micron sediment/carbon prefilter | 1237460 | Element protection and particle/chlorine duty under the product conditions |
| Thin-film composite RO element | 1238342 | Quantity, condition, seals, and replacement history |
| Granular activated-carbon postfilter | 1244746 | Final taste-and-odour stage in the original configuration |
These numbers come from an archived Merlin I performance data sheet and must be checked against the physical labels. Do not replace a component merely because its shape or Merlin name looks similar.
What Is the Pentair Merlin I Capacity?
An archived 2004 Merlin I performance data sheet lists a certified product-water production rating of 748 US gallons/day or 2,831 L/day and average system recovery of 23.7%. The figures come from standard laboratory testing; the same document states that actual performance changes with temperature, pressure, TDS, and inlet-water chemistry.
| Merlin I document parameter | Listed range or rating |
|---|---|
| Inlet pressure | 40–80 psi (2.76–5.52 bar) |
| Inlet temperature | 4.44–37.78°C |
| Inlet TDS | 50–2,000 mg/L |
| Hardness | 0–171 mg/L |
| Chlorine | 0–1.0 mg/L |
| Iron | 0–0.1 mg/L |
| Manganese | 0–0.05 mg/L |
| pH | 4.0–10.0 |
| Product-water production in certification testing | 748 gpd (2,831 L/day) |
| Average recovery in certification testing | 23.7% |
These values do not guarantee daily output at a site. During commissioning, measure dynamic pressure, temperature, TDS, permeate and reject flow, and feed/permeate conductivity. Operation outside the documented inlet conditions can reduce output or element life.
Merlin or Pentair ES60-S for a New Project?
Merlin and ES60-S are not the same model. Merlin documentation supports assessment of an existing on-demand unit and its parts; ES60-S is the Pentair under-sink RO option currently offered by Watermart. Final selection follows water quality, peak-hour flow, power, drain access, service space, and the consumables plan.
| Requirement | Option to assess | Decision evidence |
|---|---|---|
| Restore an installed Merlin unit | Merlin I and parts matched to its label/revision | Label photos, pressure, flow, conductivity, leaks, cartridge condition, and part numbers |
| Install a new under-sink RO system | Pentair ES60-S | Water test, 0.1–0.4 MPa inlet pressure, nominal 1.5 L/min demand, power, drain, and 375 × 125 × 327 mm space |
| TDS reduction is not required; sediment, taste, or odour is the main target | Pentair EU-25 or Everpure PBS-400 | TDS, chlorine, turbidity, faucet flow, cartridge format, and contaminant target |
| Sediment or hardness affects many outlets | Pentair C500 and HydraSmart before point-of-use treatment | Water test, building peak flow, pressure drop, backwash/regeneration, and installation space |
| A hotel or apartment has many drinking outlets | RO per outlet or a central RO system | Outlet count, peak flow, sanitation, maintenance ownership, reject water, distribution, and total cost of ownership |
Per-outlet RO gives each unit a clear service boundary but increases the number of systems and consumables. Central RO may reduce unit count, yet it needs engineered storage, distribution, sanitation, and monitoring. Use the hotel and apartment drinking-water guide to compare architectures without assuming that one arrangement always costs less.
Minimum Data for an Installed Merlin Assessment
Provide one evidence package that connects unit identity, inlet water, demand, and operating symptoms:
- system nameplate, cartridge labels, element labels, and all visible part numbers;
- inlet-water results, including TDS/conductivity, pH, hardness, iron, manganese, chlorine, and other relevant risks;
- static and dynamic pressure, temperature, permeate flow, reject flow, and permeate conductivity;
- installation date and prefilter, RO-element, and postfilter replacement history;
- leaks, taste/odour change, flow decline, alarms, or other symptoms;
- litres per day and peak-hour draw;
- installation space, inlet connection, drain, power, faucet, and sanitation access;
- project location, quantity, timing, and installation scope.
This evidence helps distinguish exhausted cartridges, low inlet pressure, fouling/scaling, a seal bypass, a drain fault, or the need for a system replacement. Diagnosing from permeate TDS alone can lead to buying parts that do not address the cause.
Commissioning and Treated-Water Verification
The Merlin documentation warns against using the system on microbiologically unsafe water or water of unknown quality without adequate disinfection before or after treatment. An RO system is therefore not, by itself, proof that water is ready to drink.
During commissioning, sanitise the system under the applicable model instructions, flush the cartridges and elements, check for leaks, and record pressure, temperature, feed/permeate/reject flow, recovery, and conductivity. Establish a stable baseline. Drinking-water use still requires representative sampling and laboratory verification against applicable Indonesian requirements, with sanitation and consumables logs retained.
Pentair Merlin RO Buyer Questions
Is the Pentair Merlin still available?
Complete-system, element, and cartridge availability must be confirmed at quotation because the available Merlin documents are older records. Send label and part-number photographs. For a new installation, compare the requirement with the Pentair ES60-S currently offered by Watermart.
Does the 2,831 L/day rating guarantee site capacity?
No. It is a performance-data-sheet test rating. Pressure, temperature, TDS, inlet-water quality, cartridge condition, and demand pattern change actual output. Measure capacity during commissioning and at peak demand.
Will any similar-looking cartridge or membrane fit?
No. Match the complete-system number, part number, revision, element count, connections, seals, and model instructions. Photos of the installed unit and old components are needed before selecting replacements.
Does Merlin automatically make water ready to drink?
No. Treated water must meet applicable Indonesian requirements and be supported by commissioning, sanitation, consumables records, representative sampling, and laboratory verification.
Send the installed Merlin data or new-system requirement through the PT Watermart Perkasa contact form. The quotation will confirm the model, availability, current specifications, and supply boundary in writing.