Cooler with False Bottom Dead Space Questions

[awilkes67]

HI all, pretty new to all this. I have a 10-gallon blue Igloo cooler from Lowe's that is fitted with a domes false bottom with a pipe leading out to a valve. I did some experiments yesterday to try and calculate a dead space for BeerSmith. I read on the forums that attaching a tube to the hose barb attached to the drain valve helps drainage by creating a vacuum. I did three runs using 5 gallons of plain cold water in the cooler with a tube attached draining below the cooler. In all three runs it drained almost all the way in 5 minutes with less than a quart (0.4qt) left in it consistently.

I then tried it again without the drain tube outside the cooler just letting it drip from the hose barb, it drained much slower this time, and after an hour the drip stopped with what appeared to be close to a gallon left in the cooler. I was puzzled by this result. I read that the vacuum draining effect of the tube gets more liquid out but I was very surprised to see the difference. During brewing I always use a tube, so my question is, should I use the 0.4 qt for dead space or should I plan on higher.

Or should I keep experimenting?

Also, I have recently read that tipping the cooler is bad to get more out. I have always done this and had no issues with grains coming out. Could tipping have been throwing off my water and gravity? Any opinions would be appreciated. I will try and shoot some pics of my setup today.

Here is a link to my cooler: https://www.lowes.com/pd/Igloo-10-Gallon-Beverage-Cooler/999949206

Here is a link to the false bottom kit: All Stainless Steel Mashing Made Cooler False Bottom 10 Gallon

 

[tracer bullet]

"It depends" - hah.

I can tell you my method, not saying it's right. Pour water in an empty cooler w/ the false bottom and see how much is needed to get it just peeking through the false bottom itself. I refer to that as the dead space. When I do my calculations for water to get the 1.25 - 1.50 qt / pound, I add this additional space to get a final strike water volume total (my old cooler was about 3/4 gallon, my new SS one is more like 1/4, yours will probably be in the ballpark).

As for draining, would normally just measure right in the boil kettle, which I poured into, what I got. It was almost always 1/4 gallon shy of expected with my cooler (with my old cooler, 0 now with the new SS brewtech one which has the drain hole in the bottom). I never noticed any variation in that, but I suppose I was always monkeying with things and moving the bag around, etc. and never really allowed for a vacuum. I'd check pre boil volume and gravity and decide then if I wanted to manually lift the cooler and dump out that extra quart or so.

Specifics for me though - I used a bag along with the false bottom, and I drained / poured through a hop spider just in case anything got through.

So - maybe that didn't help at all, but it's info just and ideas in case it does.

 

[McKnuckle]

The reason this happens is very simple. The height of the drain valve is above the height of the pickup at the bottom of the cooler. When you attach a hose to the barb and allow it to drop below the cooler's bottom, a siphon is established, pulling liquid from the bottom and allowing it to rise and drain out.

When you omit the tube, flow stops at the height of the drain valve itself, which means you are leaving volume in the cooler between the height of the drain valve and the cooler bottom.

A siphon will always drain to the level of the higher of its two open ends.

On the dead space issue, I would simply pour the remaining contents out over a filter and then have no dead space at all. I hate wasting recoverable wort!

 

[bobeer]

I have the same cooler with a similar false bottom. I have only used a tube if I'm brewing inside so the wort doesn't splash all over the floor. I think people are against tilting because it might disturb the grain bed that has fallen nicely on the false bottom to create another filter. I've always tilted my mlt to get the last bit out and haven't noticed any ill effects nor have I thought about it much, haha. I tend to also use a fine mesh strainer if I don't have the time to vorlauf but, either way, by the time grain bed is set not much is going to come though.

With my process I tend to worry more about end volume of the batch and how much the grain will absorb during the mash and how much will boil off during the boil. I tend to lose a gallon to the grain and a gallon to a 60 minute boil so I calculate my sparge volume based on that so I know I need all the water in the sparge and in the mlt to get to my boil volume.

 

[tracer bullet]

When you attach a hose to the barb and allow it to drop below the cooler's bottom, a siphon is established, pulling liquid from the bottom and allowing it to rise and drain out.

I'm realizing I had a slightly different picture in mind. If this is how it's set up then yes of course this is true and part of or simply the reason. My cooler had a pretty low false bottom with a drain tube coming from the top of it. I wouldn't have realistically gotten anything underneath it. Perhaps the OP's set up is indeed different and a tube can be placed underneath in which case this makes perfect sense.

I'd started to wonder if a vacuum was created by the grain bed or something, similar to putting your finger on top of a straw.

 

[McKnuckle]

In the 5 gallon cooler that I used to employ, there was a disk-shaped false bottom with a slightly concave profile facing the bottom. The drain connected via a straight piece of stainless tubing to a 90 degree fitting that was set into a hole in the center of the disk. A short length of brass tubing was connected to the 90 degree fitting underneath the disk, spanning the concave area to reach the bottom, where it rested. It had notches cut into it at its terminus to allow flow.

 

[awilkes67]

Thanks all for the input. With a tube I get an average of 0.4qt and without the tube I get an average of 2.2qt. I am glad I found this source of variation. For my next batch I will use the tube and no tip.

 

[tld6008]

Just make sure to slow the flow when you get to the point where you are relying on the siphon to drain the portion under the false bottom as you can break the siphon if its not slowed way down. I use the same method in my brew keggle but with a stainless mesh screen and I can drain all but a couple ounces under what is somtimes 8-10 ounces of hops.