The Venturi is a clever alternative to a pump: no moving parts, mostly nothing to wear out, doesn't need priming, and when the tank is full or empty it doesn't care, there's no undue load.
The whole softener seems designed to not know or care much about anything. It has stages to carry out, does them whether they are needed (or successful), and moves on to the next one after a preset time. The downside of this is that it’s up to the consumer to gauge effectiveness of softening, check if salt needs replenishing, and clean the Venturi components from time to time.

6/6

So water has been sent to the brine tank and is getting salty, how does that pipe pump the brine water out to flush through resin?
That's the job of the Venturi. Since this system has no mechanical pumps (which would add to cost and complexity) but has plenty of water pressure, they utilize pressurized water to act like a pump, running it through a clever little plastic labyrinth that results in a low pressure area that sucks brine up through pipe. This is another failure point too, since the channels and holes involved are very small and can get clogged, there’s a metal screen that filters the water and can also become coated.

5/6

Oddly, the only measuring device in the whole system is a little turbine inside the water pipe that leaves the softener. There's two small magnets rotating as water flows through with a small hall effect transistor nearby picking up magnetic pulses to send to the computer. If this gets jammed by dirt, scale, or corrosion then the spinner won't move, the computer thinks nobody is using water and will never run a recharge.
Since that's the only sensor and it’s on the water outlet, how does the system know when it’s put enough water in the salt tank? That's the job of the brine valve, a small pipe delivering water to the tank and, like a toilet float, shutting it off when water level is high enough.

4/6
#engineering #design

The softener has these stages:
1. FILL: fill the salt tank (via Venturi valve) to make brine
2. BRINE: reverse Venturi to suck brine from tank and flush through resin to removes captured calcium/magnesium
3. BACKWASH: backward flowing high pressure to rinse out dirt, sediment, iron and remaining brine from resin
4. FAST RINSE: final forward direction rinse

Two observations:
1. the salt tank only has one small hose
2. there are no pumps or sensors for these steps

3/6
#engineering #design

A quick reality check: a water softener has no idea how hard water is. That is, it doesn't have any way measure hardness. The only thing it measures is the flow of water leaving the device. Everything else is accomplished by setting approximate water hardness and then the “computer” calculates a recharge schedule based on how much resin it has, water flow, etc.. Not an exact science, so if it doesn't run often enough the water becomes hard before the next recharge cycle. If it runs too often it wastes some water and salt.

Essentially the job of a softener is to do nothing most of the time except measure water flow and decide if resin beads are full. Then spring into action, scrub the beads clean, and go back to biding its time.

2/6

In the process of fixing water softener I learned more about what it’s doing and clever bits of the design, so I thought I'd share for anyone interested.

First, a simplified version why and how we use a softener.

Hard water contains calcium (Ca2+) and magnesium (Mg2+), which binds with soap making it less effective, and can crystalize onto plumbing creating scale buildup. A typical softener contains millions (billions?) of tiny resin beads which provide a surface for these ions to bind to before they can reach plumbing. When the beads are "full” the softener does a backwash that sends salty water through the beads, stripping off the Ca2+ and Mg2+ ions and flushing them down the drain.

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