Tankless Water Heater Anti-Scale System

OFTWH-R – Up to 6 gallons per minute

This easy-to-install unit is designed to extend the lifespan of water heaters.

  • Reduces scale and improves the efficiency of water heaters
  • Helps to prevent harmful mineral build-up on heating elements
  • Replace cartridge every 2 years

Replacement Cartridge

Feed Water Chemistry Requirements


*Iron and Manganese – Just as with conventional water softening media, OneFlow® media needs to be protected from excess levels of certain metals that can easily coat the active surface, reducing its effectiveness over time. Public water supplies rarely, if ever, present a problem, but if the water supply is from a private well, confirm that the levels of iron (Fe) and manganese (Mn) are less than 0.3 mg/L and 0.05 mg/L, respectively.
Feed Water Chemistry Requirements pH 6.5 to 8.5 Hardness (maximum) 75 grains (1282 ppm CaCO3) Water Pressure 15psi to 100psi (103 kPa to 6S bar) Temperature 40°F to 100°F (5°C to 38°C) Chlorine < 2 ppm Iron (maximum) 03 mg/1* Manganese (maximum) 0.05 mg/1* Copper 1.3 ppm** Oil & H2S Must be removed prior to OneFlow® Silica (maximum) 20 ppm*** **
Copper Pursuant to the EPA drinking water standards, the copper concentration permitted is up to 13 ppm_ Typically originating from new copper plumbing, high levels of copper can foul OneFlow® media. For applications with copper concentrations greater than 1.3 ppm, please contact Watts Pure Water Technical Service at 1-800-224-1299. To further minimize any problem with excess copper, avoid applying excessive flux on the inner surfaces of the pipe and use a low-corrosivity water-soluble flux listed under the ASTM B813 standard. ***
Silica OneFlow® media does not reduce silica scaling. While silica tends to have a less significant effect on scale formation than other minerals, it can act as a binder that makes water spots and scale residue outside the plumbing system difficult to remove. This 20 ppm limitation is for aesthetic purposes.