Picture of Easy Auto Fill Humidifier
Background / Motivation:

Like many people my furnace runs much the winter,  so I need a humidifer to keep the air from getting too dry.  When the furnace runs a lot, the humidifier needs to be re-fill every day, sometimes twice a day. 

My humidfier is located in the utility room and there's a faucet nearby  - so all that was needed was a way to automatically refill the humidifer from that water source.

Basic Idea:

With just a few basic components it was surprizingly easy to create a simple auto-fill system. 

1) An electric solenoid valve & power supply - commonly used for irrigation systems and readily availabe at a Home Depot or Lowe's. 

2) A DIY float and a limit switch, this energizes the solenoid valve to refill the humidifer tank if it's low.

3) Common lamp / appliance timer (the kind you might use to turn the lights on and off while on vacation).   With this you can scheudle a few "fill check & re-fill if needed" cycles each day.

4) A few hose and electical connectors. 

You should be able to get everything locally except prehaps the limit switch, total cost should be < $50.  Say goodbye to manual refilling !!

Another Option
- Of course the best solution, allbeit at more cost and complexity, is a whole house humdifier that attaches to a forced air furnace. 

dhouggy2 years ago
This is a great project! I had been thinking about something like this but you saved me some work! I used a Lasko 1128 9-gallon humidifier which I got on Amazon for $79. http://www.amazon.com/gp/product/B000VP7FWA/ref=oh_details_o00_s00_i00

I made some mods. I used a pill bottle instead of the light bulb for a float, and screwed a dowel on top of the bottle lid that rises up and activates the limit switch. Mounted the valve and transformer externally. I had to Dremel away the inner plastic ledge at the bottom of the tank to allow enough room for the float to operate, and used eye bolts to guide the dowel of the float.

I would add that the appliance timer adds the important feature of hysteresis to the system, which lets the valve turn on and off once a day, rather than constantly be switching every time the water level drops a little bit.

Very clever!