Direct answer: The ongoing costs of a Rheem RHS32 or RHS42 are salt, water used during regeneration, a small amount of electricity, and, if you want the five-year parts-and-labor warranty, one bottle of Rheem RHWSC cleaner every four months. The manuals rate the RHS32 at 4,940 grains of hardness removed per pound of salt at its 2.6-pound minimum dose and the RHS42 at 5,010 grains per pound at 2.5 pounds; real-world efficiency is “typically less.” Rheem’s product pages claim under $5 a year in electricity and under $10 of water, from its own laboratory testing. We do not publish equipment prices because we could not verify a current price from a manufacturer source.
Publisher boundary: Water System Guide is an independent research publisher, not a Rheem retailer. This page uses the RHS32 manual 7386465 and RHS42 manual 7386473 (Rev. P, January 20, 2026) and Rheem product pages, all reviewed October 15, 2026. Dollar figures quoted here are Rheem’s own marketing claims, labeled as such. Calculations are our arithmetic and are labeled. Purchase price, local installation labor and salt prices need a current quote.
Why this page has no purchase price
Rheem’s water-treatment website does not list prices. Its product pages for the Preferred, Preferred Plus and Preferred Platinum show a “Buy Exclusively At The Home Depot” link instead (Rheem Preferred Plus product page). Retail prices change, and we did not find a manufacturer-published price to cite. Check the retailer’s current listing for the exact model number, and confirm whether the price includes installation, a bypass valve and fittings.
For typical installed cost ranges across brands, see our water softener cost guide. The rest of this page covers what the manufacturer documents do establish: how much salt and water each model uses, and what upkeep the warranty requires.
Salt: the largest ongoing cost
The specification tables rate each model’s capacity at three salt doses (RHS32 manual, PDF page 4; RHS42 manual, PDF page 4). Dividing capacity by salt (our arithmetic) shows how efficiency falls as the dose rises:
| Salt dose | RHS32 capacity | RHS32 grains per lb. | RHS42 capacity | RHS42 grains per lb. |
|---|---|---|---|---|
| Lowest | 13,000 at 2.6 lbs. | 5,000 | 12,400 at 2.5 lbs. | 4,960 |
| Middle | 27,600 at 8.3 lbs. | 3,325 | 29,900 at 8.0 lbs. | 3,738 |
| Highest | 33,000 at 14.1 lbs. | 2,340 | 42,400 at 16.3 lbs. | 2,601 |
The manuals’ own rated efficiency at the minimum dose is 4,940 grains per pound for the RHS32 and 5,010 for the RHS42. The small difference from our rounded division comes from the rating method. Both manuals add that operational efficiency after installation “is typically less than the rated efficiency, due to individual application factors including water hardness, water usage, and other contaminants.”
The controller chooses the dose at each recharge. Turning on the Salt Efficiency setting holds the softener at 4,000 grains per pound or better, with more frequent, smaller recharges. It ships OFF and must be ON in California (RHS32 manual, PDF page 16).
Estimate your own salt use
The arithmetic is simple, and you only need two numbers from a water test:
- Grains per day = hardness in grains per gallon x gallons of water used per day. Add 5 gpg for each 1 ppm of clear-water iron, as the manual’s hardness setting does.
- Pounds of salt per day = grains per day / grains per pound.
Example (our arithmetic, not a manufacturer figure): a household using 250 gallons a day of 15 gpg water removes 3,750 grains a day. At the RHS32’s rated 4,940 grains per pound, that is about 0.76 pounds of salt a day, or roughly 23 pounds a month. At 3,000 grains per pound, a more conservative efficiency, it is about 1.25 pounds a day. Multiply by the price you pay per bag of recommended salt.
Use nugget, pellet or coarse solar salt with less than 1% impurities, the type both manuals recommend. Rock salt and block salt are listed as not recommended.
Water used during regeneration
Each recharge sends water to the drain. The manuals list water use two ways:
| Water use | RHS32 | RHS42 |
|---|---|---|
| At minimum salt dose | 1.9 gallons per 1,000 grains | 2.5 gallons per 1,000 grains |
| Per regeneration at maximum salt dose | 33.3 gallons | 45.9 gallons |
Example (our arithmetic): the 3,750-grain-a-day household above would send about 7 gallons a day to the drain on an RHS32 at the minimum-dose rate. Rheem’s product pages say the softeners use “less than $10 of water per year,” a claim footnoted to “the manufacturer’s internal laboratory testing” (Rheem Preferred product page). Your water and sewer rates decide the real figure.
On the RHS42, the optional Clean feature adds a backwash and rinse before each recharge. The manual says to leave it OFF to conserve water unless the supply has iron or sediment.
Electricity
Both softeners run on a 24V DC plug-in power supply connected to a standard 120V outlet (RHS32 manual, PDF page 5). The manuals give no wattage. Rheem’s product pages claim the softeners use “less than $5 per year in electricity costs,” again from internal laboratory testing.
The same pages claim savings elsewhere in the home: “up to $558 per year in household costs” and “up to 24% on water heater electricity costs,” footnoted to a Water Quality Association soft-water benefits study. These are the brand’s marketing figures. We have not tested them, and they depend on hardness, appliances and use.
The cleaner requirement for the five-year warranty
The warranty is the cost item buyers most often miss. The standard terms are one year on parts and labor, three years on the electronic control board and ten years on the salt and resin tanks. The one-year parts-and-labor period extends to five years only if you use one bottle of Rheem RHWSC Water Softener Cleaner every four months from delivery and keep proof of purchase (RHS32 manual, PDF page 28).
That is three bottles a year. The warranty counts no more than three bottles bought in a 12-month period toward compliance, and “use of any water softener additive other than Rheem RHWSC will not provide extended warranty coverage.” The cleaner product page describes a 16 fl. oz. bottle sold exclusively at The Home Depot. The control panel reminds you: the status light flashes slowly with “CLEAn” (RHS32) or “CLn” (RHS42) after four months.
After the first year, labor is not covered even under the extended terms. Parts under warranty are shipped to the home without charge, so budget for installation labor if a repair needs a technician.
Installation items that add cost
Several requirements in the “Before You Start” section can add parts or labor to an install (RHS32 manual, PDF page 5):
- Pressure-reducing valve if daytime pressure is over 80 psi, because nighttime pressure may exceed the 125 psi maximum.
- Expansion tank if the home has a backflow preventer, per local codes.
- Licensed plumber in Massachusetts, where the state plumbing code applies.
- A grounded 120V outlet not controlled by a switch, and a floor drain or approved drain point for the valve and tank overflow lines, which must not be joined with a tee.
- A minimum water supply of 3 gpm; a well system that cannot supply it needs attention first.
Does the bigger model cost more to run?
Not necessarily per grain. At the minimum dose the two models are nearly identical in salt efficiency, and the RHS42’s 1.20 cubic feet of resin, against the RHS32’s 0.88, lets it go longer between recharges for the same household. A larger bed can also reach its rated capacity at a lower efficiency point: at the highest dose, the RHS42 removes about 2,600 grains per pound and the RHS32 about 2,340 (our arithmetic from the manuals’ ratings).
What does differ is water per recharge. A full-dose RHS42 regeneration uses 45.9 gallons against 33.3 for the RHS32, and its minimum-dose rate is 2.5 gallons per 1,000 grains against 1.9. If your water is soft enough that an RHS32’s 105 gpg hardness limit and 7.9 gpm service flow are comfortably sufficient, the smaller model may use less water. If you need the RHS42’s 9.9 gpm flow or 140 gpg limit, the extra water is part of that choice. Our Rheem models comparison covers sizing.
Frequently asked questions
How much salt does a Rheem water softener use?
It depends on hardness and water use. The RHS32 is rated at 4,940 grains removed per pound of salt at its 2.6-pound minimum dose, and the RHS42 at 5,010 grains per pound at 2.5 pounds. The manuals say real-world efficiency is typically lower.
Does Rheem publish water softener prices?
Not on its water-treatment website. The product pages link to The Home Depot as the exclusive retailer. Check the current retail listing for the exact model.
What does Rheem’s extended warranty require?
One bottle of Rheem RHWSC Water Softener Cleaner every four months from delivery, with proof of purchase, extends the one-year parts-and-labor warranty to five years. Other additives do not qualify.
How much water does a Rheem softener use to regenerate?
The RHS32 uses 33.3 gallons and the RHS42 45.9 gallons per regeneration at the maximum salt dose. At the minimum dose, the RHS32 uses 1.9 gallons and the RHS42 2.5 gallons per 1,000 grains removed.