OneFlow®+ Salt-Free Scale Prevention & Water Filtration System

OneFlow®+ Salt-Free Scale Prevention & Water Filtration System

Availability: In Stock
  • Vendor:Watts
    *Not Applicable for all promotions
$ 629.95


The OneFlow®+ system is an economical and environmentally friendly physical water treatment technology that helps protect pipes, extend the life of appliances, and provide better tasting water through filtration. The OneFlow®+ system is a dual cartridge based system with a radial flow 20 micron carbon block cartridge which reduces sediment, chlorine taste and odor, and an integrated OneFlow®+ scale prevention cartridge.

The OneFlow®+ system uses template assisted crystallization (TAC) to attract hardness minerals and convert them 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 reduced*.

The OneFlow®+ system 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 salt-free alternative to water softening (ion exchange) or scale sequestering devices.

Click here to download your OneFlow+® Anti-Scale Manual.


Bob Villa's Pick for Best Salt-Free Filtration System! See article here!

Peter Fox, Phd a professor of Environmental Engineerig at ASU and Timothy M Thomure, PE, PMP President of WaterReuse Arizona present their research and tests completed on TAC (Template Assisted Crystallization) technology). Download PDF article here!


  • Scale Prevention PLUS Water Filtration in One System
  • Protects pipes – Extends life of appliances
  • Provides great tasting water at every tap
  • Virtually Maintenance Free
  • Environmentally friendly
  • Save up to $300 annually
  • Compact Design & Easy Installation



  • Reduces sediment, chlorine taste and odor
  • Chemical-free scale prevention and protection - converts hardness minerals to harmless, inactive microscopic crystals making OneFlow®+ an effective salt-free alternative to ion exchange water softeners
  • Virtually maintenance free - no salt bags or other chemicals to constantly add or maintain
  • No control valve, no electricity and no wastewater
  • Improves efficiency of all water heating devices and downstream plumbing components
  • Simple installation – standard 1" connections
  • Excellent system for homes where equipment protection is desired for longer equipment life and reduced energy consumption
  • OneFlow®+ cartridge-based systems are easily maintained.
  • Easily installed mounting bracket and multi-function tool included to allow cartridge change-outs when necessary

NOTE:*The wetted surface of this product contacted by consumable water contains less than 0.25% of lead by weight.

Contaminant Treatment:

Sediment / Particulates: 20 microns with a dirt holding capacity up to 2.2 lbs (1 kg)
Chlorine Reduction: 50,000 gallons (189,000 liters)† @ 3 gpm (11.34 lpm)
Scale Prevention: Up to 3 years


† According to lab test of carbon block manufacturer.

Feed Water Chemistry Requirements
pH: 6.5 - 8.5
Hardness (maximum): 30 grains (513 ppm CaCO3) *
Water Pressure: 10 psi to 90 psi (0.69 bar to 6.2 bar)
Temperature: 40° F to 100° F (5°C to 38°C)
Free Chlorine: <2 ppm
Iron (maximum): 0.3 ppm **
Manganese (maximum): 0.05 ppm **
Copper: 1.3 ppm ***
Oil & H2S: Must be Removed Prior to OneFlow®+
Total Phosphates: < 3.0 ppm
Silica (maximum): 20 ppm †
TDS: 1500 mg/l ††


* Systems using OneFlow®+ technology are effective at controlling lime-scale formation inside the plumbing system at influent hardness levels up to 30 grains per gallon (513 ppm CaCO3) of calcium carbonate. Due to variances in water chemistry, 30 grains per gallon is a recommended hardness maximum due to potential aesthetic issues related to soft scale residue formation outside of the plumbing system. Testing should be performed to determine proper application where hardness levels exceed 30 grains per gallon.

**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.

***Pursuant to the EPA drinking water standards, the copper concentration permitted is up to 1.3 ppm. Typically originating from new copper plumbing, high levels of copper can foul OneFlow®+ media. New Copper lines need to be passivated for a minimum of 4 weeks before placing unit into service. For applications with copper concentration greater than 1.3 ppm, please consult Watts Water Quality Technical Service. 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.

† 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.

†† All other contaminants must meet the requirements of the USEPA Safe Drinking Water Act. Specific Mineral and Metal MCL's, identified in Watts published Feed Water Chemistry Requirements, supersedes the USEPA SDWA. Water known to have heavy loads of dirt and debris may require pre-filtration prior to OneFlow®+.


Reduction Claims Validated for this unit by WQA (Water Quality Association)

  • Model # OFPSYS.  Item # 7100638
  • MFG Brand Watts
  • Certified to NSF/ANSI 372 Lead Free
  • Certified by WQA



  • OneFlow®+ Anti-Scale Salt-Free Scale Prevention & Water Filtration System, Model: OFPSYS
  • Radial Flow Carbon Black Cartridge
  • Scale Prevention Cartridge
  • Outlet Connector
  • Multi-function Tool
  • System Mounting Bracket
  • Manual

Product Dimensions

  • UnMounted (11.375" W x 18.75" H x 8.0625" D)
  • Note: Requires a 3" Minimum Removal Clearance under housing.

(The overall height and the height of the inlet fitting varies due to material variations and assembly tolerances. Please allow additional clearance above the filter for making connections.)

What is OneFlow®?

OneFlow® is an anti-scaling water treatment technology designed to protect plumbing components, pipes, fixtures, valves, fittings, hot tanks, etc. from the negative effects typically caused by water hardness. OneFlow® is an environmentally friendly alternative to water softening or any other treatment device designed to address scale. OneFlow® prevents scale by transforming dissolved hardness minerals into harmless, inactive microscopic crystal particles. These crystals stay suspended in the water and have a greatly reduced ability to react negatively and form scale compared to untreated hard water.

How does OneFlow® differ from a Water Softener?

OneFlow® uses a specially designed media to convert the dissolved primary hardness mineral (calcium carbonate) into a relatively insoluable microscopic crystal so that it cannot cause harm downstream. A water softener, on the other hand, uses the principles of “ion exchange” to remove calcium and magnesium ions from water while replacing them with sodium ions. A water softener requires a control valve, backwashing, drain line, regeneration and a brine tank to store salt while OneFlow® requires nothing but an inlet and outlet connection.

Does OneFlow® remove the important minerals in water?

No. OneFlow® preserves the beneficial mineral content while preventing the possible negative scale formation associated with these minerals. By rendering the hardness minerals harmless while still keeping them present, you truly get the best of both worlds. Other treatment methods fall short. In a 2005 report on Nutrients in Drinking Water, the World Health Organization writes…“We conclude that hard water is good because it contains nutrients valuable in themselves…To minimize heart disease risk, the ideal water should contain sufficient calcium and magnesium to be moderately hard."

What factors may effect OneFlow®'s system performance?

Water chemistry and peak fl ow rate are the guidelines used to assure optimal system performance. Most municipally treated (city) water falls well within our performance guidelines to ensure scale control results. However, there are chemistry limitations related to possible foulants and interference ions. Water known to contain visible dirt and debris must be strained using a wye-pattern strainer or equivalent (100 mesh) before OneFlow® tank systems. More details are available on the product datasheets and IOMs. As with any water treatment technology, correct sizing of the system is important to ensure proper performance. However, OneFlow® is more forgiving of flow variations and unplanned peaks than a conventional water softener.

How easy is it to install a OneFlow® system?

For anyone who has ever installed a Water Pressure Reducing Valve or a Backflow Preventer, installation of a OneFlow® system will be relatively easy.

What are the ongoing maintenance costs and considerations for OneFlow®?

One of the great benefits of the OneFlow® technology is the dramatically reduced maintenance requirements. Other than the planned media replacement, there is nothing else required. For tank systems, the media replacement is once every three years, and for filter housing systems, it's once every 2 years. That's it.

Why is OneFlow® a "Green Technology"?

OneFlow® s truly a “Green product” because it saves water and energy in the following ways:

  1. Reduces Energy Consumption – OneFlow® uses no electricity and reduces energy consumption by keeping heat transfer surfaces free of energy-robbing scale formation.
  2. Reduces Chemical or Raw Material Consumption – OneFlow® requires no chemical or significant ongoing consumable (salt, as an example).
  3. Reduces Waste Water Discharge and Water Consumption – Because OneFlow® does not discharge or require backwashing it meets both objectives.
  4. Reduces Space Requirements – OneFlow® systems use approximately 75% less floor space than water softeners.
  5. Retains nature's minerals in the water. The beneficial minerals, calcium & magnesium, are completely retained.
This warranty will be void if defects occur due to failure to observe the following conditions:

  • OneFlow®+ systems are warranted for domestic use in residential single family dwelling applications excluding irrigation water treatment. The use of these systems in light commercial, commercial, or industrial applications will void their limited warranty.
  • The OneFlow®+ system must be installed in applications with municipally supplied water adhering to EPA guidelines.
  • Any component failure must not result from abuse, fire, freezing or other acts of nature, violence, or improper installation.
  • Equipment must be installed and operated in compliance with the local plumbing codes and on an approved water supply.
  • Equipment is limited to use at water pressures and temperatures that do not exceed our published specifications.
  • Water supply must not exceed 3.0 PPM chlorine. For water supply exceeding 3.0 PPM chlorine, pretreatment is required. (Please contact your water treatment specialist.)
  • Information, including model number, serial number, and date of installation, must be provided for any claims pertaining to equipment in warranty.
  • Defective parts are subject to inspection by either Watts Regulator Company or any authorized representative before final commitment of warranty adjustment is made.
  • Watts Regulator Company reserves the right to make changes or substitutions in parts or equipment with material of equal quality or value and of then current production.

Your Rights Under State Law

Some states do not allow limitations on how long an implied warranty lasts, and some states do not allow the exclusion or limitation of incidental or consequential damages. Therefore the above limitations may not apply to you. This warranty gives you specific legal rights, and you may have other rights that vary from state to state. You should consult applicable state laws to determine your rights. SO FAR AS IS CONSISTENT WITH APPLICABLE STATE LAW, ANY IMPLIED WARRANTIES THAT MAY NOT BE DISCLAIMED, INCLUDING THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ARE LIMITED IN DURATION TO THE APPLICABLE WARRANTY PERIODS STATED ABOVE.