Upflow vs Downflow Softener Regeneration Explained

The short answer

In downflow (co-current) brining, brine flows down through the resin the same way water does in service. In upflow (counter-current) brining it flows up, against the service direction, so the least-exhausted resin at the bottom, the last resin water passes before your taps, is regenerated most thoroughly. Makers of upflow valves describe lower salt use for the same softening.

Side by side

Brining direction
	Downflow	Upflow
Brine direction	Same as service	Against service
Common on	Many timer and older metered heads	Many newer high-efficiency heads
Maker claim	-	Less salt for the same softening

Does it matter to you?

Less than capacity, flow and a metered valve do. If salt use matters, a metered valve and a correct hardness setting save more than the brining direction alone. Size the softener first.

Salt efficiency

Water Conditioning & Purification notes that salt efficiency falls as the salt dose rises: its example softener gets 4,000 grains per pound of salt at a light setting but about 1,867 at 7.5 lb per cubic foot.