Reliability of auto drains is probably in the same range of statistical probabilities as an operator's attentiveness and short term memory. It is assumed that a compressor equipped with auto drain is normally used to fill multiple tanks or a cascade. In any case, with respect to the conditions under which the compressor operates, it is a fact that the condenser will accumulate more or less moisture and that it must be drained. However, it is not necessary to dump every drop, just enough to allow the compressor to continue to function reliably. Since most moisture is voided in the first three seconds I see no problem with drain activations lasting a few seconds when viewed in terms of the rather short drain cycles recommended by the mfgrs, eg, every fifteen minutes. Very little moisture can accumulate in a small compressor in so short a time. I would suggest a 3-4 second dump in the average time to fill one S80, about 25 minutes.
My strategy has always been to equip all compressors, even small compressors (4 cfm) with a large condenser equpped with BP valve. This is followed by a hybrid condenser/filter, IOW, the second unit is an aluminum cylinder with micronic separator in the bottom and filter canister on top. Thus, there is a large primary condenser fitted with a BP valve, which can hold up to five ozs of water, and normally traps virtually all liquid moisture. Additionally, there is a secondary condenser/filter which holds about 1.5 ozs. The manufacturer of the large condenser, Walter Kidde, says that drain intervals can be up to 2 hours although I usually activate the drain every hour. When drained, no gas is lost from the secondary canister due to the BP valve on canister #1. When draining gas from the secondary, not one drop of water has ever been visible when the drain was activated regardless of humidity. Nothing but air comes out.
