Watts OneFlow Anti-Scale OFTWH System


Watts OneFlow Anti-Scale OFTWH System   Ideal zero waste and zero maintenance alternative to salt or liquid softeners   Peak flow rate 22 litres per minute making it ideal for most homes   Change cartridge only every 2 years   No chemicals added to the water (unlike liquid or salt softeners)   How does it … Conti... More description
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Watts OneFlow Anti-Scale OFTWH System


  • Ideal zero waste and zero maintenance alternative to salt or liquid softeners
  • Peak flow rate 22 litres per minute making it ideal for most homes
  • Change cartridge only every 2 years
  • No chemicals added to the water (unlike liquid or salt softeners)


Watts oneflow installtion

How does it work?

The OneFlow® Anti-Scale System provides protection from scale formation on internal and external plumbing surfaces. The OneFlow® system is a single cartridge-based system that must be installed on a cold water line prior to a water heating device (water heater or tankless water heater) for single tankless heaters.

OneFlow® prevents scale by transforming dissolved hardness minerals into harmless, inactive microscopic crystal particles.These crystals stay suspended in the water and are passed to drain. The system requires very little maintenance, no backwashing, no salt and no electricity. Typical hardness problems, especially build-up of scale in heating elements, pipes, water heaters, boilers and on fixtures are no longer a concern.

OneFlow® is not a water softener. It does not add chemicals. It is a scale prevention device with proven third party laboratory test data and years of successful commercial, residential and food service applications. OneFlow® is The Intelligent Scale Solution™ and is a great alternative to water softening (ion exchange) or scale sequestering devices.


  • Chemical-free scale prevention and protection – converts hard-ness minerals to harmless, inactive microscopic crystals making OneFlow® an effective alternative technology to a water softener for the prevention of scale due to water hardness
  • Virtually maintenance free – No salt bags or other chemicals to constantly add or maintain
  • No control valve, no electricity and no wastewater
  • Uses environmentally friendly “green” technology
  • Improves efficiency of all water heating devices and downsream plumbing components.
  • Simple sizing & installation – standard 3/4″ connections
  • Perfect system for restaurants, cafeterias, coffee shops and homes where multiple or single equipment protection is desired for longer equipment life and reduced energy  consumption
  • Inlet ball valve for easy isolation shutoff and filter changes
  • OneFlow® cartridge-based systems are easily maintained; change the cartridge once every two years
  • Easily installed mounting bracket included w/filter wrench to allow cartridge change-outs when necessary
  • Media certified for material safety toNSF/ANSI Standard 42 and 62


Download Spec Sheet

Watts OneFlow Anti-Scale  OFTWH System  OFTWH

Watts OneFlow FAQs

watts one flow oftwh questions


Watts OneFlow Anti-Scale  OFTWH System  OFTWH

Download Manual

Watts OneFlow Anti-Scale  OFTWH System  OFTWH




Model Watts OneFlow Anti-Scale System OFTWH
Brand Watts
Filter Parameter Limescale
In Depth

The OneFlow® Anti-Scale System will condition the tap water providing optimum water characteristics for their specified applications. The result is reduced equipment maintenance requirements, longer equipment life and improved quality & consistency of your products. The OneFlow® system is built with the finest and most advanced materials and each system is quality inspected and pressure tested prior to shipment. With proper installation and routine maintenance, you will have years of trouble-free operation. Please refer to this manual when performing routine filter changes. The instructions make periodic maintenance quick and easy and ensure you will receive maximum benefit from your system.

Style: Single Cartridge
Connection Sizes: ¾ in. (20mm)
Flow Rates: 0.5 to 10 gpm (1.9 to 38 lpm)
Applications: Tankless water heaters

System Specifications

Maximum Pressure:
90psi/620.1 kPa

Maximum Temperature:

Inlet/Outlet Connections:
3/4″ 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.

OFTWHRM cartridge does not have a grain removal capacity, however, other contaminants present in the water will gradually degrade the effectiveness of this cartridge. Change the OFTWHRM cartridge at least once every two years.

Independent scientific testing has confirmed Template Assisted Crystallization (TAC) technology provides scale reduction of over 95+%. Testing was conducted under protocol based on DVGW W512 test to access control of scale formation

Water Chemistry & Limitations

6.5 to 8.5

Hardness (maximum)
75 grains (1300 ppm CaCO3)

41°F to 100°F (5° to 40°C)

< 3 ppm

Iron (maximum)
0.3 mg/l

Manganese (maximum)
0.05 mg/l

none allowed

Oil & H2S
none allowed

none allowed

Silica (maximum)
10 ppm


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