Show or Hide

OneFlow® Model OFTWH Anti-Scale System

The Intelligent Scale Solution™ for Tankless Water Heaters

Tankless water heaters with their tightly packed, small gage tubing are prone to the overheating and malfunction that result from scale formation.

Today there's a solution to this problem – OneFlow® Model OFTWH. The same water treatment technology that’s been used successfully in commercial plumbing is now designed to ensure scale-free tankless heater operation in your home or small business.


  • Compatible with all major tankless water heater brands
  • Maintains manufacturer's stated water heater efficiency
  • Works to prevent heater malfunction due to scale build-up
  • Diminishes existing scale problems and costs associated with de-scaling
  • Environmentally friendly alternative to water softeners
  • Designed for tankless water heaters up to 10 gallons per minute
  • Virtually maintenance free - no salt or chemicals to add or maintain
  • No Electricity or backwashing required
  • Simple sizing & installation with standard 3/4" connections and included mounting bracket
  • Inlet ball valve and filter wrench for easy shutoff and filter changes
  • Long lasting OneFlow® cartridge – change once every two years

A Breeding Ground for Scale

Hard scale can accumulate over time on pipes, valves, fixtures and heating elements. Heat increases the tendency for limescale deposits to form; the higher the heat the greater the buildup. Tankless hot water heaters, designed to operate at high efficiency, can be a breeding ground for scale. Once formed, these scale deposits result in malfunctions and calls for service.

Single Cartridge; Easily Installed

The OneFlow® Anti-Scale System provides protection from scale formation on internal and external plumbing surfaces. The OneFlow® Model OFTWH is a single cartridge-based system that is easily installed on a cold water line prior to a tankless water heater. Once installed, the system requires very little maintenance, no backwash, no salt and no electricity. It is truly The Intelligent Scale Solution™.


To learn more about OneFlow® anti-scale technology and how it can solve your scale problems, visit or contact your Watts representative.

Pressure – Temperature

  • Maximum Pressure: 90psi/620.1 kPa
  • Maximum Temperature: 100ºF/38ºC
  • Minimum Temperature: 35ºF/2ºC

Inlet/Outlet Connections

  • ¾in. FNPT

Service Flow Rate

  • 0.5 gpm to 10 gpm (1.9 Ipm to 38 Ipm)

Gallon Rating:

  • OFTWH: up to 6 gpm, 24/7/365 for 2 years for the OFTWHRM.

Get Adobe Acrobat

Please Note: Watts literature requires Adobe Acrobat Reader to view.

Featured Item

Water Quality Products Catalogue

Get your copy of the latest Watts Water Quality Products catalogue. Includes information on Watts' full line of residential & industrial filtration systems, water softeners, parts & accessories and test equipment.

To obtain your copy, click here.

Technical Services

Frequently Asked Questions

Want to know more about Reverse Osmosis or Water Softeners? Visit the Watts Water Quality Products Frequently Asked Questions pages.