• Water Doctor 4-stage undersink reverse osmosis system
Water Doctor

Water Doctor 4-Stage Undersink RO System

$799.99 CAD $899.99 CAD
11% off
SKU: ROS4A
Traditional undersink RO system with storage tankThe Water Doctor 4-Stage Undersink RO System is a complete drinking water solution for homes that prefer a reliable storage-tank reverse osmosis setup. It...

In stock and ready to ship

Water Doctor 4-stage undersink reverse osmosis system
$799.99 CAD

Before you choose a drinking-water system

Compare flow rate, storage style, and filter maintenance with Water Doctor if you are not fully sure this is the right RO system for your household.

Get Drinking Water Advice Talk to Water Doctor

If you are still diagnosing the problem, use one of these tools before you commit to checkout.

Water Diagnosis Check Water Hardness Rule out a whole-home hardness problem before solving only the drinking-water tap. Guided Selection Help Me Choose Use the guided path to compare RO, whole-home filtration, and hardness-led next steps.
Estimated delivery: Jun 25 - Jun 29
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Traditional undersink RO system with storage tank

The Water Doctor 4-Stage Undersink RO System is a complete drinking water solution for homes that prefer a reliable storage-tank reverse osmosis setup. It includes the core components needed for everyday drinking water, including the RO system, tank and faucet.

Best for

  • Households looking for a proven undersink RO setup
  • Customers who prefer a storage tank system over tankless RO
  • Daily drinking, cooking, coffee and tea
  • Homes upgrading from bottled water or basic pitcher filters

Key benefits

  • 4-stage reverse osmosis filtration for better-tasting water
  • Storage tank design provides ready-to-use RO water
  • Dedicated drinking water faucet for convenient kitchen use
  • Genuine ROS4A replacement cartridges available for maintenance
  • Practical residential option for many standard kitchens

Maintenance

Use Water Doctor ROS4A quick-twist replacement cartridges for routine filter changes. Replacement timing depends on water quality and household usage.

Installation note

This is an undersink RO system. Professional installation is recommended for faucet drilling, tubing setup, drain connection and leak testing.
  • Water Doctor 4-stage undersink reverse osmosis system
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  • Free Assessment

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  • Installation Planning

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  • Shipping and Support

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  • Replacement Ready

    Keep maintenance, filters, and UV lamp replacements simple over time.

    Buy with more confidence

    Water Doctor is strongest when product, installation, and maintenance are treated as one system.

    • Confirm the Right Fit

      Match this product to your water problem, household size, and plumbing setup before checkout.

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      Plan Installation

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    • Think About Maintenance

      Replacement filters, UV lamps, and long-term care should be part of the buying decision from day one.

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    Before you order

    Need help confirming fit, installation, or maintenance?

    Water Doctor can help you verify whether this product matches your water problem, installation setup, and replacement schedule before checkout.
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    After purchase support

    Keep performance high with the right replacement and service plan.

    Water treatment performance depends on timely maintenance. Save your model details, set replacement reminders, and use Water Doctor support when unsure about cartridges, UV lamps, or service intervals.
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    Replacement and maintenance essentials

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