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Installation, Operation and Maintenance Manual


Inflow Installation InstructionsThe Watts OneFlow® system provides protection from scale formation throughout the plumbing system. The OneFlow® system can be installed at the point of entry to treat your entire system, both hot and cold water, or it can be located directly before a water heater or other device (e.g. steamer, etc) that requires protection from hard water. OneFlow® reduces or eliminates scale formation on internal and external plumbing surfaces as well as reducing spotting and streaking normally associated with hard water. OneFlow® prevents scale by transforming the normal dissolved hardness minerals into undissolved crystal micro-particles. These crystals stay suspended in the water and have a greatly reduced ability to react and attach to surfaces like dissolved hardness does. Therefore, the problem of internal buildup of scale in pipes, water heaters and on fixtures and glass is greatly reduced. OneFlow® is not a water softener – Low or phosphate-free cleaning products are recommended to achieve optimum results. Modern surfactant or detergent based, liquid soap are preferred over old-fashioned caustic solid soaps. Unlike softened water, OneFlow® treated water maintains the beneficial essential mineral content of your water and is safe to drink.

OneFlow® Benefits

  • Chemical free scale prevention. Provides cost savings and environmental benefits
  • Virtually maintenance free. No salt bags or other chemicals to buy, transport and store
  • No electricity, no wastewater, completely self-contained
  • Beneficial minerals retained for more healthful drinking water
  • Improves the efficiency of water-using appliances.
  • Simple installation – no electrical and drain hookup
  • Safe for landscaping and lawn watering. No need for costly bypass plumbing
  • Compatible with all on-site and community wastewater treatment systems
  • Not subject to water softener restrictions and “bans”

OneFlow Systems Overview 1

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Oneflow System Overview 2


Equipment Specifications

Watts OneFlow® systems are complete, self-contained, loaded with media and ready to use. A simple inlet and outlet connection is all that is required for installation. Please review operating pressures, temperatures and water chemistry limitations to ensure compatibility.


Oneflow Equipment Specifications

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Inlet/Outlet Connection3/4" - 11/4" (multiple options)
Temperature40° - 110°F
pH6.5 to 8.5
Ferrous Iron, Max*0.3 mg/L
Manganese, Max*0.05 mg/L
Copper, Max*1.3 mg/L
Water Pressure (psi)15psi min., 100psi max

* See note about iron, manganese and copper on the next page.

Mechanical Specifications
Max Service Flow
Dry Weight (lbs)2225293543
Service Weight (lbs)8097129168235
Dimensions (nominal - inches)

Using OneFlow® with other water treatment equipment.

Due to the unique properties of OneFlow®, there are some unique requirements for using OneFlow® in conjunction with filtration or other forms of water treatment.

1. OneFlow® must be the last stage in the treatment chain. Do not install any filters after OneFlow® or before any devices for which scale prevention is required. POU drinking water filters, e.g. carbon or RO are exempt from this requirement.

2. Do not apply phosphate or any other antiscalant either before or after OneFlow®.

Important note about iron, manganese and copper in the water supply

Iron and Manganese

Just as with conventional water softening media, OneFlow® 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. However, 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. Copper should be less than 1.3 mg/L.


Copper usually originates from new copper plumbing upstream of the OneFlow® system. If this condition exists, we recommend waiting 3-4 weeks before placing the system in operation. This will allow the copper surfaces to be fully flushed and develop a natural protective surface. To further minimize any problem with excess copper, avoid applying excess flux on the inner surfaces of the pipe and use a low-corrosivity water soluble flux listed under the ASTM B813 standard. Once the plumbing connections are complete, place the OneFlow® system in bypass prior to following the startup procedure and flush the plumbing for at least 10 minutes.


  • Do not let the system freeze. Damage to the tank may result.
  • System must be operated in a vertical position. Do not lay it down during operation. The system may be placed in any position for shipping and installation but must be operated in the vertical position.
  • Place the system on a smooth, level surface. Because the system operates in an UP-Flow, fluidized bed mode, having a level surface is more important than with a softener or media filter.
  • A bypass valve should be installed on every system to facilitate installation and service.
  • Observe all local plumbing and building codes when installing the system.

Notes to the Installer

The OneFlow® system differs from a conventional softener or media filter in a number of key respects.

  • The system is light and only partially filled with media. This is normal. The UP-flow operation of the system requires a lot of freeboard to allow the bed to fully fluidise.
  • The system has no underbed so you can tip the system over without any fear of upsetting the media. This makes transportation and installation much easier than conventional systems.
  • Because the OneFlow® system operates in the UP-flow mode, the tank connections are opposite of traditional installations.
  • Please see the “Important note about iron, manganese and copper in the water supply” above.
  • Please see the note about “Using OneFlow® with other water treatment equipment” above.

Installation and Start-up


Oneflow Installation & Startup

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1. Place the system in the desired location.

2. Connect the cold water supply to the inlet of the OneFlow® system.

NOTE: The OneFlow® system operates in the UP-flow mode which is opposite of a conventional softener.

3. Place a bucket under the outlet port or run a line from the outlet port to a drain.

5. Slowly open the supply valve (user supplied) to the OneFlow® system. Allow the tank to fill with water. Close the supply valve when a steady stream of water comes out of the outlet port.

6. Connect the outlet of the OneFlow® system to the cold water supply of the building.

7. Open the supply valve to the OneFlow® system.

8. Open faucets downstream from the OneFlow® system to relieve any air.

9. Check for leaks. Repair as needed.

10. The system is now ready for service.


Bypass Valve Modification

Note to the building owner

Your OneFlow® system will improve the properties of water throughout your building. Here are some things to expect and some recommendations for maximizing the benefits and your enjoyment of OneFlow®

Sinks and fixtures – should have little or no spotting. If water is allowed to evaporate off a surface, small spots may be left behind. This spotting should not require any more than a wet cloth or sponge to remove. No harsh chemical should be required as with typical hard water spotting.

Dishwasher-Spotting on dishes and on the surface of the dishwasher should be greatly reduced or eliminated – We recommend that you immediately reduce the amount of dishwashing detergent by approximately 50% as compared to hard water use. Dishwashing detergents low in phosphates are highly recommended as they are better for the environment and phosphates can cause spotting. In very hard water areas, the use of a rinse aid may be advised.

Shower doors and tiles – should have little or no spotting. When water evaporates off a surface, small spots may be left behind. These spots should be easy to remove with a damp cloth or sponge.

In the bath – you should notice that soaps and shampoos lather more than with un-treated water. Soaps and shampoos will also rinse off much easier and faster than they would with traditional soft water. We recommend the use of modern soaps for the best results.

Things to watch for:

During the first 30-90 days:

  • Faucet aerators and drains may plug occasionally as old scale is removed from your plumbing system and water heater.
  • You may also see milky water while the descaling is taking place. This is simply an increase in the calcium in the water because OneFlow® is removing old scale deposits from your pipes.

Good practices:

If your dishwasher is severely coated with scale at the time of installation, we recommend that you purchase a product like Jet-Dry® Dishwasher cleaner to accelerate the cleaning. After this initial cleaning OneFlow® should keep it clean. We also recommend that you drain your water heater tank. This should be done 30 to 60 days after OneFlow® is installed, and again in one year. This is a good practice that can dramatically increase the life of your water heating appliance. The OneFlow® will help keep the tank and heating elements free of scale and operating at peak efficiency. Please follow the manufacturers instructions when draining the tank!

Limited Warranty

  • The OneFlow® tank system is warranted to be free of defects in materials and workmanship for 5 years from the date of original shipment.
  • The OneFlow® media is warranted for performance for a period of 2 years from the date of the original installation when installed and operated in accordance with the instructions in the corresponding Installation and Operation Manual.

Watts Regulator Company warrants its OneFlow® cartridge systems as follows:

  • The OneFlow® cartridge system is warranted to be free of defects in materials and workmanship for 1 year from the date of original shipment.
  • OneFlow® cartridges are warranted for performance for a period of one year from the date of original installation when installed and operated in accordance with the instructions in the corresponding Installation and Operation Manual.
  • Carbon replacement filter cartridges are not warranted to perform for any period of time because the service life of replacement carbon filter cartridges varies significantly with local water conditions and volume.


  • 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 2.0 PPM chlorine. For water supply exceeding 2.0 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.


Our obligation under this warranty with respect to the tank or valve is limited to furnishing a replacement for, or at our option, repairing any part or parts to our satisfaction that prove defective within the warranty period stated above. Such replacement parts will be delivered to the owner F.O.B. nearest factory, at no cost, excluding freight and local labor charges, if any.

Our obligation under this warranty with respect to the OneFlow® media will be limited to furnishing a replacement for the media within two years from date of original installation. Such replacement media will be delivered to the owner F.O.B. nearest factory, at no cost, excluding freight and local labor charges, if any. Damage to the media due to chlorine, other oxidizers or fouling caused by local water conditions or any other operation outside of the limits shown under Specifications, is not covered by this warranty.


The remedy described under this warranty shall constitute the sole and exclusive remedy for breach of warranty, and Watts Regulator Company shall not be responsible for any incidental, special or consequential damages, including without limitation, freight, handling, lost profits or the cost of repairing or replacing other property which is damaged if this product does not work properly, other costs resulting from labor charges, delays, vandalism, negligence, fouling caused by foreign material, damage from adverse water conditions, chemical, or any other circumstances over which Watts Regulator Company has no control. This warranty shall be invalidated by any abuse, misuse, misapplication or improper installation of the product. 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