I’m setting up my new mash tun. It a 16 gallon ss mash tun with a false bottom that I will the direct fire. I got a pump and I have notched the lid for the out hose from the pump to go through and made a manifold. My question is do I want the manifold to be a little below the top of the mash or above it sprinkling down on the mash? Thanks
You want it on top of the mash, not sprinkling. Sprinkling the mash water induces oxygen. I assume the holes are in the top of your manifold? You want the mash water level above your manifold.
As long as you have a pool of wort above your grain bed, there is no need to sprinkle wort over the bed. Just return the flow into that pool and you’ll gain every advantage and the flow will spread evenly. If you create some sort of mash cap that floats over the wort, you will further reduce oxygen contact.