OneFlow Anti-Scale System for Water Heaters

OFTWH (Up to 10 GPM)

Install on the supply line to storage type or tankless water heaters to reduce the formation of scale on the heating elements. This helps to keep the heater working efficiently, reducing the cost of operation.

  • Replace cartridge every 2 years
  • 3/4″ connection size

Replacement Filters

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.