Why drain valves fail
Nine out of ten dead drains we replace failed for one of four reasons. None of them is the valve.
The first cause is sludge. Compressor condensate is not water; it is water with oil, rust and thread tape in it. A float drain with no strainer lets that mix reach the seat, and the float sticks open or shut within a few months. Every BRISOL timer drain has a Y-strainer in the body. Clean it at every service.
The second is timer setting. A drain set to open for a few seconds every half hour, on a receiver that fills with condensate in ten minutes, will flood. Start with a short interval in the monsoon and stretch it until you hear a puff of air at the end of each discharge. That puff means the receiver is empty.
The third is voltage. A 220 V coil on a 24 V panel, or a 24 V coil on a line that dips under load, both burn out. Check the coil label against the supply before you wire it, and measure under load, not at idle.
The fourth is location. A drain on the receiver alone does nothing for water that condenses downstream in a long pipe run. Put one drain at every low point: receiver, aftercooler, the filter bowl before each FRL, and the end of the main.