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.