I built mine. It's made a big difference in my brew day.
Here's how I use it.
1) add the strike water to the MLT (2nd tier) and start heating with the burner under it (drink a HB)
2) once the strike water is up to temp, add grains and dough in (drink a HB)
3) about 1/2 way through the mash, add sparge water to HLT (3rd tier) and start heating with the burner under it (drink a HB)
4) once mash is done, sparge/lauter (using your favorite technique) into the boil kettle (1st tier) and begin the boil (drink 2 HBs)
5) chill the wort (using your favorite technique) and xfer into the fermenter (drink a HB)
I can give you the dimensions if you want. I just drew it out on paper, got out the chop saw and the welder (1st time) and went to town.
I've got the pump now, but it's not necessary
. It just gives me the option to do some things like recirculate the mash and recirculate through my CFC back into BK. Since I built it intentionally low, I can't gravity drain from the BK, so I used to use a wort wizard
before I bought the pump.