Water softeners

This is the part sales pages are vaguest about, so it is worth being blunt. No single stage treats everything, and buying the wrong one for your water is the most common way people end up with expensive equipment that changes nothing.

The tank is filled with resin beads carrying sodium ions. Hard water passing through them trades its calcium and magnesium for that sodium, because the resin holds the hardness minerals more strongly. The water leaving is soft; the hardness stays on the beads.

Eventually the resin runs out of sodium to trade. The unit then regenerates: it draws concentrated brine from the salt tank, flushes it through the resin at high concentration, and sheer numbers force the exchange to run backwards — the hardness comes off, sodium goes back on, and the hardness goes to drain.

That is the whole mechanism, and understanding it explains the limitations. There is nothing in ion exchange that addresses a dissolved gas, a bacterium or a nitrate ion. It is a trade, not a filter.

Softeners are sized on grain capacity — how much hardness they can remove between regenerations. The calculation is straightforward: how much water the household uses, multiplied by how hard the water is, multiplied by how long you want between regenerations.

Two things trip people up. The first is that iron and manganese consume capacity too, roughly four grains per gallon for every part per million, so a modest iron level meaningfully changes the size you need. The second is that advertised capacity is measured at maximum salt dose, which is the least efficient way to run the unit — sizing against about three quarters of the rating gives sensible salt use.

The target is regeneration roughly weekly. Much more often and you are wasting salt and working the resin hard; much less often and the bed goes stale and channels.

Size a softener for your water→

They are not softeners, and the naming is the problem. A salt-free conditioner does not remove calcium and magnesium — the hardness is still in the water when it comes out. What these systems do, usually via template-assisted crystallisation, is convert dissolved hardness into microscopic crystals that are less inclined to stick to surfaces.

That has real value for one specific thing: scale in pipes and water heaters. If your only complaint is scale, a conditioner may genuinely solve it with no salt, no drain connection and no regeneration water.

It will not fix the other symptoms of hard water, because the hardness is still there. Soap will not lather better, spotting on glassware will not improve, skin and hair will feel the same, and a hardness test on the outlet reads exactly what went in. If those things are why you want a softener, a conditioner will disappoint you.

A genuinely salty taste is not a normal result of softening. Ion exchange adds sodium in proportion to the hardness removed, and at typical hardness that is far below the threshold where anyone can taste it. If the water tastes salty, something is wrong rather than working.

The usual cause is a valve fault leaving brine in the treated water — a stuck brine valve, a blocked drain line, or an injector that is not clearing the brine tank properly at the end of the cycle. The tell is timing: the taste is strongest right after a regeneration and fades over the following hours.

Two other explanations are worth ruling out. Very hard water genuinely does produce enough sodium to be noticeable to some people, which is a case for potassium chloride or an unsoftened kitchen tap. And chloride already in the well — from road salt, a septic influence or seawater intrusion — tastes salty whether or not there is a softener, and shows up on a test as chloride above the 250 mg/L secondary standard.

• Salty only after regeneration — a valve, drain or injector fault. Call for service.
• Salty all the time with a softener fitted — check chloride on a water test.
• Salty all the time with no softener — chloride in the well, and reverse osmosis is the practical fix for drinking water.

Softening adds sodium in proportion to the hardness it removes — about 8 mg of sodium per litre for every grain per gallon of hardness taken out. For most water this is a small number in the context of a normal diet, and considerably less than many people assume.

It is worth taking seriously in two cases: genuinely very hard water, where the arithmetic mounts up, and anyone on a medically restricted sodium intake. The usual answers are to use potassium chloride instead of sodium chloride in the brine tank — it works identically and costs more — or to leave the kitchen cold tap unsoftened, which is a plumbing decision best made at installation.

Softened water is also slightly more aggressive toward copper than hard water, which matters if your pH is already low. That is a reason to fix pH properly rather than a reason to avoid softening.