There is what looks like a 90 degree drain hose out of the bottom of the heater core area on the firewall. Yesterday afternoon when the truck was started, water ...

There is what looks like a 90 degree drain hose out of the bottom of the heater core area on the firewall. Yesterday afternoon when the truck was started, water came out of this tube. Fan on only, no AC. It is running down the edge of the plastic inner fenderwell and dripping behind the right front tire. It is definately water and not antifreeze. I understand water coming out while the truck is running / AC on. I just wasn't sure about a puddle of water when the truck was initially started with the AC off.

Last couple of days has been dry here, no rain. Truck is an 04 Silverado ecsb Z71 with the 5.3.

Is this normal?

Yes. Probaby the last time you drove the truck, you had it on defrost which turns on the compressor which "makes water".

Word of advice from Gordon. ALWAYS turn your blower on high for a few seconds before you park the vehicle to "blow out" any water that may have accumulated in the heater/ac case (vehicle with ac only). Long term, it will prevent any bad odors that develop from standing water within the case.

Also high humidity will make for more water run off

Thanks for the advise. To me, as long as it wasn't oil, anti-freeze or brake fluid, no reason to worry about it. I more curious as to what was going on.