new mash tun question

I am building a new mash tun using a 10gal round orange igloo cooler. I made the manifold out of pvc in the shape of an octogon. Just curious as to what everyone else has experienced as their lauter tun dead space? I did a quick test run with about two gallons of water. After the liquid quit running, it looked like there was almost 3/4 gallons left. I was in a hurry and didn't have time to measure to be sure.

thanks

You should be able to tilt the mash tun an collect all but maybe a quart or so. IMO, it's best to allow for some losses when formulating your recipe and don't stress about grabbing every last drop of wort. It's just not worth it. I fly sparge, so most of the time what is left behind contains almost no sugar anyway. I can see wanting to get as much out of the MT as possible when batch sparging, but I would not go to much trouble to do so when just adding a pound or so of extra malt to the recipe is often enough to cover minor losses.

BTW, you might want to switch to cpvc rather than us the pvc. The cpvc is designed for higher temperatures and I'm in doubt about the safety of using regular pvc in this application.

Sounds like your manifold is not resting flush on the bottom of the cooler or the hole/slits are facing upwards. The siphon created when draining should draw out most of the wort and not leave 3/4 of a gallon behind.