Mash out questions on brew day

I brewed a Dopplebock this past weekend. Been doing all-grain for over a year now and this was, by far, my biggest grain bill at 16lbs for a 5.5 gallon batch. Boy was THAT fun to grind all that grain and it start to overflow a 5 gallon homer bucket!

On to my questions:

last two brews I did decoction mashes. First time I missed my temps because I didn't pull enough of a decoction to raise the temps to the desired level. I resorted to adding some boiling water to get it to correct temps.

Saturday, I did a single decoction and the goal was to raise the temps from 158 to 169 with this decoction. I boiled the decoction for some time (30 min+) and then opened the mash tun to dump it in. I waited for conversion using iodine test. Reading here said I should have conversion about 20 minutes, but it took quite a bit longer. Closer to 50 min. My temps in the mash tun dropped 10 degrees, probably due to the fact that I had it only half full and also that I didn't pre-heat. I tried to compensate for that with a higher strike temp, but that obviously didn't work. So, again, I had to resort to mash out at 159 degrees. After that time, everything was converted and since I didn't hit mash out temps at 170, I only waited 5 minutes before I started lautering.

(Grain bill was simple: Weyer pilsner malt, munich I, carared.)

Does a mash-out matter in this case? What I mean is, should my efficiency be the same whether or not I did a mash out, correct? Last two brews I missed my mash out temps and my efficiency was LOWER than when I do a mash out. Also, last two brews I did decoction mashes (and MUCH longer mashes) and I read that usually bumps up efficiency. Not once did the temps go over 160, so enzymes should have been still working.

Grain crush has been the same last 6 brews, and efficiency has dropped from low 80's to low 70's. The only thing different from brews in the past is my water. I now use RO water that I add calcium carbonate to it to get my calcium levels up to snuff. The pH hasn't been a problem and stays in the 5.2-5.6 range. This could, perhaps, be the problem with less efficiency.

I am not worried about it, really, just more curious than anything.

Second question: the two brews within the last few months that I did with 80+ efficiency numbers lautering was VERY slow (45 min to get 7 gallons.) This was mainly because I hadn't finished cutting the slots in the copper manifold I built and I did it a bit fast and got stuck. Initially, I thought that perhaps this slow lautering helped, so I purposefully did it slow on the two lagers that had 70's efficiency. I do batch sparging, if I need more into the boil kettle. Does lautering speed have anything to do with efficiency IF the mash is fully converted?

Thanks!

The temperature shouldn't affect efficiency that much. A hotter mash out is thinner so it flows a bit easier. Flow rate is more likely to affect efficiency if your flow rate is too fast, but as long as it isn't so fast that your lauter gets stuck, it shouldn't have that big of an effect. Although if you go too fast, you might leave more wort behind in the grains than you thought.

I like to drain my mash without adding any water, and then do 2 equal sparges and get very good efficiencies. I use my pump for the initial drain and to pump out the first sparge. For the final sparge I use the pump to vorlauf and then let it drain slower by gravity. I put the first two runnings on to boil and then add the final sparge when it is done. (which also means I don't have to lift as much at once)