Aprilaire / Generalaire 4040 Humidifier Solenoid Valve

I''m an HVAC technician, and have replaced dozens of these. Remember to order an Aprilaire 4004 In-Line Strainer and the correct orifice for your humidifier model when you order this solenoid valve, because it doesn''t come with them. If you forget the orifice, don''t be surprised when water starts gushing out of the humidifier, because the orifice regulates the amount of water fed to it. The strainer goes in the long end of the solenoid fitting, and the orifice in the short end.

Aprilaire 4231 Yellow Orifice: Aprilaire models 400, 500, 550, 550A, 560, 568 & 600.

#4021 Aprilaire Red Orifice: Aprilaire models 112 & 224.

#4232 Aprilaire Blue Orifice: Aprilaire models 350, 360, 440, 700, 760, 760A & 768.

#4007 Aprilaire White Orifice: Aprilaire models 110 & 220.

About a week ago I noticed that when my furnace was off...my Aprilaire humidifier just kept running. Well, to be more specific, the water flow into the Aprilaire was remaining on. At first I feared the control system in the furnace was failing to send the "close valve" signal. But a bit of investigation uncovered the culprit: the solenoid valve was "leaking"! When the furnace was running, it dutifully sent an "open valve" signal, and the solenoid fired as usual, sending water to the Aprilaire. But when the furnace shut off (and/or the humidity set point had been reached), the signal to "close valve" was properly sent, but the solenoid did not fully close. The water supply decreased, but there was significant leakage passed the seat of the valve, causing the water to run down the drain 24x7.

Option 1 was to call my furnace company and have them come replace it. My guestimate was $100-150 to make that happen. While they are normally worth every penny, in this case I struggled to justify spending that much for so simple a fix. So I started snooping on the web and found this replacement part here on Amazon.

I could not be HAPPIER! It took me all of about 10 minutes (and I am NOT a skilled plumber!) to swap out my old solenoid for this one, wire it up, and give it a try. It works PERFECTLY! Now, to be clear, you will need some tools. An adjustable wrench and screw driver are musts obviously, but what some people may overlook is you may need a copper tubing cutter. When I removed the old one, the old copper fitting would not fit properly in the new solenoid, so I had to cut it off and installed the new fitting that came with this valve. Other than that, installation was a breeze!

Let me clarify a few items that I saw mentioned in other reviews:

First, this solenoid DOES ALREADY have a strainer on the inlet! Do not waste your money buying a new one, as recommended in other reviews and as shown in the "bundle" in the ordering area on Amazon. The filter is built in, and in fact if you bought another, you would be unable to make it fit.

Second, this solenoid DID FIT in the exact mounting holes that the old one used. Maybe I was just lucky, but I saw others say theirs did not fit. Admittedly the tubing routing had to be shifted a bit (this solenoid is not the exact same size as the old one), but the mounting holes lined up perfectly.

Finally, YES you must use a yellow orifice (or whatever color is right for your Aprilaire) to restrict flow on the outlet... BUT before you buy one, take out your old solenoid and see if you ALREADY have one that is in good shape! I wasted a few bucks on a new yellow orifice when in fact the old one was perfectly fine and went right back into service with the new solenoid.

It remains to be seen how long this solenoid will last, but I am VERY happy with this one so far. With about 10 minutes of work I saved myself probably $100 in repair fees and now my water is not running down the drain 24x7!

Buy Aprilaire / Generalaire 4040 Humidifier Solenoid Valve Now

This company does not ship what is pictured. They ship a cheaper imitation part from China. It will work but does not fit like the original. They should be ashamed of themseves for misleading people with what is described and pictured. I went with this company for all the good reviews and thought that I would get what was pictured to avoid the cheaper imitations. I will complain to Amazon but at least the part does work for now or at least the last 15 minutes as I just installed. I also gave them a 1 star for misrepresentation.

Read Best Reviews of Aprilaire / Generalaire 4040 Humidifier Solenoid Valve Here

The HVAC company did a winter tuneup on our furance. They mentioned our Aprilaire 550 humidifer wasn''t working and quoted $230 to repair it (including a new solonoid). I bought this solenoid and a maintence kit (pad, hose, etc.) on Amazon all for $70 including shipping. Simple 30 minute install and the humidifer is working like new again. You can''t go wrong with this product if you have an Aprilaire 550.

Want Aprilaire / Generalaire 4040 Humidifier Solenoid Valve Discount?

I have a history of a recurring problem of the valve malfunctioning every year. The valve manufacturer is some outfit in Wisconsin and they charged almost $100. Sure enough, the valve failed again in one year. So this is the 3rd I have replaced. I will see if it lasts. One thing I notice is that this is heavier and a bit larger than the OEM valve. It is quieter and has a more solid feel to it. It fit the mounting fine on my Aprilair 440, no problems there. They do not give you a new in-line screen or a flow-reduction fitting, but all I did was turn the tap-in valve from my water source lower and that controls the amount of water flowing into the humidifier, so who needs them and why pay another $10? Works great. Its been 3 weeks and so far working fine. I''m hoping...

I did purchase this from Amazon.

UPDATE: This is my second heating season (2013) and this valve is still going strong, no problems with the valve or humidifier. As I said above, this valve is built much heavier that the original factory model. I am very pleased.