How does that red LED light on my Drain Master switch work?  We are asked this by customers about 5 times a week. So we thought it might be a good idea to explain how in detail here.

In simple terms if the light is on, the valve is open (to some degree.)  If it is off, the valve is fully closed.  So in other words, if you close your valve and the light stays on, chances are, something is stuck in the gate path.

Light ON = valve OPEN

Light OFF = valve CLOSED

Now if you are the type of RVer that prefers to know “how” it works, then keep reading for a technical explanation.

Your switch should look like one of these. 



The Magnetic Switch we will be referring to in this article is on the back of the valve and looks like this.






First we need to start with the 12vdc power going to the operator switch from the coach battery. If we use a wire placed on the + (positive) terminal of the battery and run it to a magnetic switch placed on the back of the Drain Master valve and then run the wire from the magnetic switch through an LED light and terminate the wire by connecting it to the – (negative) terminal of that same battery, the LED light would light up.

Now if I take a magnet and place it over the switch on the valve the light will go out, remove it and the light will go back on. What we have done is glued a magnet on the gate in a precise position so when the gate is in its closed position the magnet is lined up under the switch.

Battery + —————-Magnetic switch N/C———-LED light————Battery –

The dash lines indicate the wire.

There you have it, simple and effective. If the light is OFF the valve is CLOSED. If the valve gate is in any other position the light is ON.

If your magnetic switch is not working you can replace it. The part# is 5016 and they are $5.98 ea and come with complete replacement instructions. You can find it here.