Teddy> Lastly, what are you using for the return into the mash-tun?
Teddy> I'm thinking of about 4' of 3/8" OD soft copper tube with big
Teddy> slots in it to allow grains to pass through.  I want to connect
Teddy> it to the hose with a simple worm clamp...  Is this what you're
Teddy> doing?

Well, I used to use a slotted return manifold, but I found it got
clogged with grain.  Now I have something much simpler to make.  All
made of copper 1/2" rigid and fittings.  Hose fitting at the top,
vertical pipe long enough to reach from the grain bed up and overthe
top of mash tun.  On bottom of vertical pipe, a copper T.  From the
copper T, short pipe sections in both directions, then in both
directions, another tee, short piece of pipe another tee, short pieces
of pipe and 45 degree elbows.  Looking from above, here is a try at an
ASCII graphic
                                                            
            x                          x                    
            |      x                   |                    
            |      |                   |                    
            |      |                   |                    
            |-------------O------------|                    
            |                    |     |                    
            |                    |     |                    
            |                    x     |                    
            x                          x                    
                                                            

The "O" in center represents the tube coming down from the top.  The
X's srepresent 45 degree elbows.  The 45 degree elbows are rotated up
from horizontal about 45 degrees and then crushed in a vise so that
they are oval, rather than round, but now that I have been using it a
while, I think the crushing may not be necessary.

You can attach this to a 100psi water source and turn on the water
full force and only get gentle flows out of the 6 open ends.

The manifold is lowered onto the grain bed and held in place from
falling over by a clamp of some sort.  The manifold comes out through
a hole in the lid of my Gott, but if you cannot do this, you could
revise the configuration so that the vertical tube is right at the
perimeter of the mashtun and the mashtun would then support it.