Rheem
Rheem Preferred Platinum 42,000 Grain Smart Water Softener (RHW42)
$689
Best Water Softeners · head-to-head
Rheem Preferred Platinum 42,000 Grain Smart Water Softener (RHW42) vs A.O. Smith 40,000 Grain Water Softener (AO-WH-SOFT-400T)
A sourced, side-by-side comparison. A.O. Smith 40,000 Grain Water Softener (AO-WH-SOFT-400T) is cheaper at $549. Every spec and price links to its source.
A.O. Smith
A.O. Smith 40,000 Grain Water Softener (AO-WH-SOFT-400T)
$549Cheaper
Which is better: the Rheem Preferred Platinum 42,000 Grain Smart Water Softener (RHW42) or A.O. Smith 40,000 Grain Water Softener (AO-WH-SOFT-400T)?
On the specs we track, they're closely matched. The A.O. Smith 40,000 Grain Water Softener (AO-WH-SOFT-400T) is the cheaper at $549.
See Rheem Preferred Platinum 42,000 Grain Smart Water Softener (RHW42) on Amazon See A.O. Smith 40,000 Grain Water Softener (AO-WH-SOFT-400T) on Amazon
As an Amazon Associate we earn from qualifying purchases. Prices verified at capture; live price may differ.
Full spec sheet
✓ marks the stronger figure where "more" — or "less", for price and weight — is unambiguously better.
| Spec |  Rheem Preferred Platinum 42,000 Grain Smart Water Softener (RHW42) |  A.O. Smith 40,000 Grain Water Softener (AO-WH-SOFT-400T) |
|---|---|---|
| US price | $689 | $549 |
| Brand | Rheem | A.O. Smith |
| Released | — | — |
| Grain capacity | 42.4 | 40 |
| System type | ion-exchange | ion-exchange |
| Flow rate (gpm) | 9.9 | — |
| Salt efficiency lbs per kgrains | — | — |
| Iron removal (ppm) | 11 | 10 |
| NSF certifications | — | — |
| Smart app control | Yes | No |
| Tank warranty years | 10 | 10 |
| Msrp (USD) | 689 | 549 |
Sources — Rheem Preferred Platinum 42,000 Grain Smart Water Softener (RHW42): rheemwatertreatment.com (verified 2026-06-26). A.O. Smith 40,000 Grain Water Softener (AO-WH-SOFT-400T): aosmithatlowes.com (verified 2026-06-26).
What's the difference between the Rheem Preferred Platinum 42,000 Grain Smart Water Softener (RHW42) and A.O. Smith 40,000 Grain Water Softener (AO-WH-SOFT-400T)?
Where the two actually differ on the specs we track (4 of 9). Matching specs are omitted.
- Grain capacity: Rheem Preferred Platinum 42,000 Grain Smart Water Softener (RHW42) 42.4 vs A.O. Smith 40,000 Grain Water Softener (AO-WH-SOFT-400T) 40
- Iron removal (ppm): Rheem Preferred Platinum 42,000 Grain Smart Water Softener (RHW42) 11 vs A.O. Smith 40,000 Grain Water Softener (AO-WH-SOFT-400T) 10
- Smart app control: Rheem Preferred Platinum 42,000 Grain Smart Water Softener (RHW42) true vs A.O. Smith 40,000 Grain Water Softener (AO-WH-SOFT-400T) false
- Msrp (USD): Rheem Preferred Platinum 42,000 Grain Smart Water Softener (RHW42) 689 vs A.O. Smith 40,000 Grain Water Softener (AO-WH-SOFT-400T) 549