Do I need a water softener?

The honest answer is a number, and you do not have it yet

Almost everything written about this question describes symptoms and then sells you a system. There is a measurement that settles it, and This Old House gives both the scale and the threshold:

Hardness is reported in parts per million (PPM), milligrams per litre (mg/L) or grains per gallon (GPG), counting calcium and magnesium. PPM and mg/L are two ways of saying the same thing, and one GPG equals about 17.1 PPM or mg/L. The GPG figure is a number between 0 and 20, and anything at seven or above is considered hard water.

So the question "do I need a water softener" has a form that can actually be answered: what is your GPG?

Getting the number

This Old House gives three routes, and we have put them in the order we would use them:

Our recommendation, marked as ours. Start with the utility report, because it is free and immediate and will often tell you straight away that you have nothing to worry about. If it puts you anywhere near seven, spend the ten dollars on your own kit rather than taking the free test first. The free test is not a trick and the reading is probably fine, but it is performed by the company that would sell you the system, and a ten dollar kit removes that question entirely. If you are on a well, the utility route does not exist and the kit is the starting point.

The symptoms that should send you to the test

Fixr lists what hard water does, and this is the list worth checking yourself against:

• A film on your sink, tub or dishes
• Stains or buildup on the showerhead or coffee pot, hard to remove and hardening over time
• Soap that will not lather properly
• Laundry that does not feel clean, or feels scratchy and stiff
• Dry, itchy skin and hair that feels dry and tangles easily
• Higher water bills, because things need rinsing more often to get the soap film off
• Decreasing water pressure, and appliances that stop working or need frequent plumbing repairs as deposits build up

A This Old House homeowner on one of its New Jersey projects described the same thing in plainer terms:

When we moved in there were green rings around the toilets. I tried cleaning it with bleach, vinegar, and we ended up just changing out the toilets.

Its plumbing and heating expert put the mechanism in one line: hard water "is really a question of how many minerals are absorbed in the water", in that case magnesium and calcium, which leave stains on sinks and toilets and wreak havoc on water heaters.

Our note, marked as ours, and it is the reason this page exists on a cost site. That last clause is the expensive part, and it is the part nobody connects. Hardness minerals come out of solution when water is heated, which is why the deposits land in the tank rather than in the cold pipe. Our water heater lifespan page covers how much life that costs you, our sediment and noise page covers the sound a limed-up tank makes, and our anode rod page covers the part that is supposed to take the damage instead. If you have hard water and a tank heater, the softener is not only a comfort purchase.

What the number then tells you to buy

Hardness decides capacity, not house size. This Old House: a softener is sized on grain capacity, meaning how many grains of hardness it removes before it has to regenerate, and most residential units run 24,000 to 64,000 grains, handling families of two to six people.

Two consequences it names, and both are worth reading before a salesperson gets to them:

• Too small and the system runs constantly, wears out faster, and still leaves you hard water at peak times.
• Too large and you have paid upfront for a system that sits mostly idle, with the possibility of stagnant water.

Above 20 GPG, This Old House says the system may need additional servicing through the year, and a dual-tank system becomes worth considering for a continuous supply.

Our reading, marked as ours. This is why the ten dollar test comes before the quotes rather than after. Capacity is the one number on the quote that cannot be judged by eye, and it is the one that a contractor can inflate without it looking like anything. Walk in with your GPG and the conversation changes.

So: do you?

Our summary, and it is ours rather than any publisher's:

• Below 7 GPG. No. Fix the specific annoyance if you have one, and keep the money.
• 7 to 20 GPG. Probably, and the case is strongest if you have a tank water heater, since that is where the damage concentrates. Our water softener cost page puts a whole-house system at $1,100 to $3,000.
• Above 20 GPG. Yes, and ask about a dual-tank system and a servicing schedule rather than taking the cheapest quote. Our regeneration page explains why hardness drives both, and our maintenance page prices the upkeep.
• Taste or smell rather than scale. That is a different problem and a softener will not fix it. Our softener versus filter page sorts out which machine handles which complaint, and our reverse osmosis page covers the equipment for dissolved solids.