To remove solids in the water, which are primarily calcium and magnesium, you need to soften the water. If you want to remove everything, a small RO unit will work. If you're going to soften, you may as well do all the household water to get the benefit of softened water for cleaning, etc. It will be pretty costly to adequately treat water for just your humidifier.

Aliceinwonderland is right on the mark.

No simple filter will remove hardness. An RO will remove pretty much everyhting from water except the "H" and the "O" but RO water is aggresive and your humidifier may not like it.

To remove hardness you need an ion exchange water softener and the right way to soften is to treat the whole house.

Better to cure the disease than treat the symptom.

Get a comprehensive water test from an independent certified lab and look to a local water treatment professional to advise you on your specific needs. You may be surprised to find out what else is in your well water and what may be in there might hurt you and your family.

thanks so far...

what is RO?

RO = Reverse Osmosis

If your water is coming from an untreated well I can't stress strongly enough that you NEED to have your water tested by a certified lab. Aside from the extra wear and tear on your plumbing, fixtures, and appliances from hard water there are health concerns that may need to be addressed.

I live in a small town in New England. My water comes from a town well. They monitor the water closely and take pride in how it is free of bad things. Though hard, the water doesn't seem to be so hard as to be damaging anything. I get 10 yrs out of my water heaters, and lived here 20 years with no plumbing-related issues.

How can RO water be 'aggressive'? Acidic maybe?
/j

"They monitor the water closely and take pride in how it is free of bad things".

I'd have to see a water test before I believe it "is free of bad things".

Google "RO water is aggressive"

They test it frequently and send out reports annually. I personally know the head of the Board of the Water District - they really take serious that the water has to be healthy.

that search was interesting - maybe a fine particulate filter will work for me?

NO SIMPLE FILTER WILL REMOVE HARDNESS. Forget about ANY simple filter.

Hardness can be removed by ion exchange (water softener), distillation, or a membrane technology like an RO. If you feed an RO hard water the membrane will clog in short order and they are not cheap to replace.

What is your buddy at the water district reporting for hardness, iron, manganese, TDS, sodium, bacteria in your water?

If your humidifier is the only place you have a problem, your cheapest, easiest solution is just to replace the pad more often. Humidifiers are really difficult because only pure vapor (mostly) exits the humidifier, so you are concentrating everything in the water. This will happen even with softened water. It may be a bit slower, but you will still get build up, just a different type of buildup (softer, less tenacious). The purer your water, the less build-up you will see. Even healthy water has plenty of stuff dissolved in it.

Bottom line, RO is the only practical method for your situation. Nothing else you can install will remove dissolved solids from your water (softeners swap one solid for another). At a cost of around $400, it may not make financial sense when humidifier pads are fairly inexpensive.

One other option may be to install a flush valve to periodically empty the humidifier of all water and then refill it. This would prevent solids from becoming so concentrated.

our water quality:

http://sudburywater.com/
select "water quality" from the home page

Thanks aliceinwonderland - not what I wanted to hear, but helpful. The tablets keep the solids in the pan easy to clean, but the belt collects the solids and then they get 'baked in'. Not sure the flush would help unless I did it weekly (and it's not a flush, have to remove the drum and then dump the pan manually).

I guess I'll just double up on the belts (2 per heating season @ $12 each)

thanks
/j

If you are getting an extra belt, try throwing the old one in the tub with a gallon of white vinegar. This might dissolve all the hard water particles. Could also dissolve the filter but you won't know if you don't try.

thanks, but that gallon of vinegar will cost almost as much as a new belt! 8-)