165 qt. Mash Tun Dead Space

[dciolek]

Just did some testing on the 165qt mash tun cooler with CPVC manifold I hooked up today.

One happy thing -- with a 100qt hot water test -- it held the temperature to a 6.5 degree drop in 10 hours -- so less than 1 degree per hour, which works for me.

However, when I drained the cooler -- which uses a CPVC manifold with slots on the bottom 1/3 to 1/2 of the 3/4" tubing inside and a drain pipe that has to lift above the level of the manifold in order to exit -- it leaves between 10-11 quarts of water in the cooler after a full level drain.

Now I know that when it has grain in there, the amount of liquid that is lost will be MUCH less than 10-11 quarts. But, does that seem reasonable?

Wondering if there is a design flaw.

If not -- how much free draining wort will be lost where there is a grain bed in there (in other words -- what is the volume of water that can be drained from 10-11 quarts of saturated grain/wort combo.

 

[grathan]

I can't fathom where 11qts is, how high up on the pvc in the picture?

 

[dciolek]

The cooler has a rather large footprint. The photo is only showing about half -- the drain line is connected to the exact middle of the manifold.

The water level stops almost to the top of the CPVC pipe that is laying flat in the cooler (not the drain line that is above the surface of the main manifold lines). It is below the height of the elbows and tees. Makes me think it is stopping just about at the level where the topmost portion of the inner diameter of the pipe is.

But I expected it to drain down to the level of the slots in the CPVC -- which is closer to 1/3 through the section of the pipe (at most halfway through due to some errant cuts in a few slots). You can just barely see the slots in the top pipe in the photo.

Maybe I need to test it by lowering the output level of the exit, such that it is siphoning as much as it is draining out of the cooler?

 

[dciolek]

Yes -- it is the siphoning effect.

With just the outlet valve hooked up, so it drains horizontally (into my sink for the test), the water level stopped at the top of the inner diameter of the manifold pipe.

With an extra length of 3/4" siphon hose attached to the exit valve and the outlet of that hose placed 3 feet below the level of the cooler exit valve -- the water stops at a level consistent with where the slots are cut through. It even gives a noticeable "sucking" sound through the manifold as it starts to approach the terminal level, and takes a bit more liquid with it during that time. Total liquid remaining was 3.75 qts instead of 11 qts (which means more in the brew kettle).

So the moral of the story is (duh) -- you are going to get more wort drained out of a cooler mash tun that uses a slotted manifold system (with an exit pipe with a section above the level of the main manifold) if you take advantage of the siphoning effect and attach an outlet hose to the mash tun exit valve and direct it to a lower level (hmm, let's say the bottom of your boil vessel that is gravity fed below your mash tun).

Which I know is pretty much a general practice anyway to keep from introducing too much oxygen to the wort pre-boil (Hot Side Aeration).