The Stovebolt Site Forums The Shop Area The Tool Chest Cheap self emptying air compressor water valve?

I'd been planning on installing built-in air compressor lines for my garage with manual water drain valves, but then stumbled across automatic water drain valves ($168 each) which is probably what the Big Boys use. Heck, that's almost as much as I paid for the compressor!

Instead, I was thinking there's got to be a better (cheaper) way - maybe just a small chamber with a ball float/stopper. See my other post about a 220v timer switch, and I came up with a cool idea...

With the air pressure on, the ball float would be held down and seal the chamber, so it would eventually fill with water. Once the compressor turns off (using some sort of countdown timer switch) and the pressure leaks down, the ball float would rise and the water would let itself out.

Simple, eh? Now I just need some suggestions on where to find a ball float chamber which can stand up to high pressure and is relatively cheap. Then I've got a zero maintenance system!

Any ideas where to start looking? Thanks!

-Boyo

I have seen automatic drains in Harbor Freight and Northern Hydraulics for MUCH less than $168.

I would think you could put one of these drains in wherever you want and just run a small line from the unloader side of the compressor to the drain valve.

Another alternative might be to use an electic air solenoid that opens for a second or two right after the compressor kicks off.

After a bit of searching, found exactly what I need: automatic drain valve , $2.35 each.

This should work for air, but I'm not 100% certain...only one way to find out! Maybe a small pressure reducer so that 150psi doesn't blow this out, but should be OK. Whatcha think?

As soon as the compressor leaks down to 4psi, the system drains itself. Perfect!

-Boyo

boyoconnor, the pressure is WAY too low. I like the way you are thinking though... I don't think the pressure reducer would work. But let us know.

Hmm, not sure I understand - too low?

The valve would close above 5psi, and would open below 4psi. So if you shut off the compressor, the water would drain out automatically.

Or did you mean the part wasn't intended for 150+psi pressure? That's my worry, was thinking a $6 pressure reducer could solve that problem.

Obviously this wouldn't work if the compressor were on all the time.

-Boyo

boyo, standard water drain systems crack open the drain at 3-5 psi. If you wanted this to work really well, just plumb in a solenoid valve that works off the same circuit as your timer from the other post. When the timer goes off for the night, it closes the outlet from the tank. Then the downstream system will leak down and the water drain valve will open and pee water all over your floor. Of course, you should design in some leaks so that your system will bleed down after the solenoid valve shuts.

i used a spitter valve that we use on the big trucks.

when the air compressor cycles off at max pressure a air line signals the spitter valve to discharge water keeping air tank dry.

you can get info on plumbing valves ect from your local big truck dealers

There are some good ideas in the above posts, but I'm going to try to give you insight into your original question.

1. What you are worried about is the DIFFERENCE in the pressure on either side of the valve, not the total pressure. If you use a design that is set up for a 3-5 psi pressure differential, make sure that you have a recieving vessel for the water that is pressurized to the same pressure (or a little less) as the main tank. In this way you can make a cheap valve do the work of an expensive one (old engineering trick). This is called pressure referencing. You could drain the main tank into a small air reserve tank, for example, then at regular intervals shut off the smaller tank from the larger and drain.

2. Typically, any floatation valve that uses a ball inside of it uses a ball that is hollow - ie very sensitive to differences in pressure. If you replace it with a SOLID ball of plastic, the ball will still float - although it may sit deeper in the water (less bouyant) so it will tend to open later than when the hollow ball will. Solid balls won't collapse under the pressure difference, hollow balls will.