Rheem® PREFERRED Plus Water Softener

42,000 Grain Large-Capacity System

The Rheem® PREFERRED Plus™ 42,000 grain water softener can handle the soft water demands of households of any size. This softener has a robust feature set that provides maximum value, flexibility and exceptionally soft water throughout your home. Like the other Rheem® models, this one uses built-in Rheem® Learning Technology to adapt to your household water usage which conserves water, energy, salt* and saves you money. It is just as easy to use as it is effective with simple onboard programming, no filter replacements required, adjustable hardness level, low salt alerts and an easy-to-load salt tank.

* For peak performance in your high-efficiency Rheem water softener, evaporated salt pellets or solar salt crystals with less than 1% impurities are recommended. We do not recommend using any kind of block salt in the Rheem water softeners. Learn more.

Water Softener Savings

Rheem® Learning Technology

Learns your home’s water usage patterns to optimize salt consumption, provide on-demand soft water for your home, and maximize overall softening efficiency.


Ideal for All Household Sizes

Large 42,000 grain capacity ensures soft water is available when you need it for large households.

Maximum Water Pressure

Ultra high flow valve maintains water pressure in up to 1-1/4″ plumbing and homes with multiple bathrooms.

Soft and Clean Water

The built-in sediment filter keeps sediment out of your plumbing with no filter replacements needed.

Easy Salt Loading

Large tank opening with hinged cover makes loading salt fast and easy. Includes an illuminated tank light for better visibility.

Adjustable Water Hardness Level

Water hardness level is fully customizable with an external blending valve to keep ideal-quality water flowing through your home.

Lasting Quality

Durable, high-impact salt storage with an internal double-lined mineral tank will not deteriorate, rust or corrode. The tanks are guaranteed for 10 years.

Low Salt Monitor

A blue status light flashes slowly to let you know when it’s time to add salt.

Eliminates Unsightly Stains

Removes clear water (Ferrous) iron that causes reddish-brown stains to form on toilets, showers and sinks.

Made in the USA

Rheem® Water Softeners are designed, engineered and manufactured right here in the USA.

Backed with Industry-Leading Warranties

1-year on parts and labor (extendable to 5-years***), 3-years on electronics, 10-years on tanks.


*Based on findings from the Water Quality Association soft water benefits study.
**Based on the manufacturer’s internal laboratory testing.
***The 1-year can be extended to five years with the use of Rheem Cleaner – see warranty page for more information

Tech Specs

RHS42 Tech specs chart. These values and more appear in a textual form in a table below.
Model CodeRH42
Rated Softening Capacity (Grains @ Salt Dose)42,400 @ 16.3 lbs.
Rated Efficiency (Grains/Pound of Salt @ Minimum Salt Dose)5,010 @ 2.5 lbs.
Rated Service Flow Rate9.9 gallons per minute (gpm)
Amount of High Capacity Ion Exchange Resin1.20 cu. ft.
Pressure Drop at Rated Service Flow12.0 pounds per square inch (psi)
Intermittent Flow Rate @ 30 psi pressure drop22.4 gallons per minute (gpm)
Water Supply Max. Hardness140 grains per gallon (gpg)
Water Supply Max. Clear Water Iron11 parts per million (ppm)
Water Pressure Limits (min. / max.)20 – 125 (psi)
Water Temperature Limits (min. / max.)40 – 120 °F
Minimum Water Supply Flow Rate3 (gpm)
Maximum Drain Flow Rate2.0 (gpm)
Dimensions:Height: 48″
Width: 15-1/4″
Depth: 20-1/2″

Extend Your Warranty and the Life of Your Softener

A little maintenance goes a long way to ensure your water softener maintains optimal performance. Adding Rheem® Water Softener Cleaner every four months can make all the difference. Plus, with regular use, you can extend your 1-year parts and labor warranty up to 5 years.

More About Rheem Softener Cleaner
Preferred Series Water Softener Cleanser Bottle

Owner Resources

Find answers to all of your water softener installation and maintenance questions

Rheem® PREFERRED Plus™ Installation Guide

Need help installing your water softener? Follow this guide.

View Guide

Rheem® PREFERRED Plus™ Product Manual

Use the product manual to learn everything you need to install, operate and maintain your softener.

View Product Manual