Please understand that my case for the use of water below is not intended to argue with anyone, before I was given a AWNS as a beta tester for Todd, I was completely happy with the smoked food (mainly ribs & pork butt), coming out of my MES. In fact it was good enough that people asked me to supply smoked pork butt or ribs for birthday's, wedding rehearsal dinners, graduation parties, etc. The only problem was having to tend the MES by adding wood chips every 30-45 minutes. Todd's AWNS and later AWNPS has been a fantastic accessory that works and is a great help to MES owners. When I started using the AWNS and later the AWNPS, my goal was to get more smoke time with less tending, and to NOT deviate to far from the system/methods I was using to produce great tasting Q, which meant to continue using water in the water pan. So after using alum foil tents, and several other improvised methods, the best/simple solution that worked is below.
Regarding water in the water pan, you can follow whatever advice or your own inclination. However I disagree with the advice to not use water with one exception. Todd's advice is based on using the AWNPS, thus if you were NOT using any of Todd's smoke accessories, then the use of water in the water pan is fine. The reason given for NOT using water in the pan with the AWNPS or the AWNS is there is so much water/humidity moisture that it prevents the AWNPS from staying lit.
Understand the MES was designed to use with water in the pan. Also know that water vapor or steam has been found to be very beneficial to smoking meat, moisture helps the meat absorb the smoke flavoring at a great rate. You can see this in competition BBQ now, even wood fired pits many use a water pan inside their smoker. I have shared previously, a family friend with a degree in food science who sells smoke enhancing products that apply smoke to meat in industrial quantities, has backed up that moisture is better than no moisture for the reasons mention in smoking meat. In the MES the water pan is also part of the MES system to keep temperature steady.
Therefore if you can keep the pellets or sawdust dry and lit, water in the water pan is a better method of smoking meat than without. (NOTE, the EXCEPTION, everyone has their own preference, some just like things dry, that is their particular taste, but in general according to science and pro BBQ smokers moisture is the better way to go, delivering a better tasting product.)
While many have complained about moisture/water streaming down their MES windows, I have yet to hear anyone saying the inside bottom of their MES has a pool of water. I wonder how many will confess that the moisture is primarily at the beginning of their smoke when the metal inside surfaces are cold and as the air heats up and steam is released so does condensation, just like your car wind shield, until the heat is great enough to overcome the condensation.
NOTE my MES 40 is only 800 watts, most MES 40 are 1200 watts, however water boils at 212º, I run my smoker between 220º - 250º, and so do most of us smoking pork butt or ribs, thus the moisture content inside the MES will be about the same regardless if 800 or 1200 watts. In fact my lower wattage MES the element has to stay on longer vs the 1200 w which will cycle more to maintain temp so I would guess the 800w would produce even more moisture.
My solution to keeping the AWNPS pellets dry is:
This is one of those throw away aluminum roasting pan, you can buy them at most grocery stores or target, etc. I used what I had laying around, the width was perfect , the length required that I cut it in half and fold the two pieces together then cut the openings. (In upper left you can see the seam of the cut.) There are two 3/4" holes on the back side.
I put the AWNPS with well lit pellets and the alum cover on the two horizontal support bars for the heating element (left side of the cabinet). The lit end is facing the back wall, not sure why this works better but it does.
The heat from the pellets will reflect off the alum and keep the pellets dry, in fact you will eventually notice the pellets start turning a darker color from that heat as long as they are lit and smoldering.
I have also pointed out that using this setup I can even use regular wood chips in the AWNPS and they will stay lit and smoke, although only about an hour+. Which do you think is harder to keep lit, sawdust, pellets or wood chips? There is a reason Todd sells sawdust and pellets not wood chips. So if this setup can smoke wood chips and keep pellets or sawdust dry in my MES it should work just fine in anyone's MES and they can use the water pan with water, as designed by Masterbuilt and preferred by experts.