Mash tun dead space and impact on efficiency

[BrewHark]

I recently switched to a new mash tun set-up. It is a 10 gallon ss kettle with a ss false bottom (purchased from homebrewstuff.com). I use it for 5 gallon batches. Problem: I haven't been able to hit my OG target...not even close. For example, yesterday I brewed a beer with a target OG of 1.071. I ended up at 1.056! I think I know the problem, but first I wanted to share the process and get your thoughts.

7 lbs 2 row
5 lbs white wheat
2 lbs torrified wheat
3 oz crystal wheat
Crusher set at .048" (too loose?)

I have a well, so I used distilled built up with salts (tsp each of calcium chl, epsom salt, gypsum, baking soda). Using PH strip, mash appeared to be just a tad on the plus side of 5.4.

1.25 qts/lb

Single infusion 152F @ 60 minutes. 149F at the end of the mash. No mash out (should I?) Sparge water 170F.

Now here is where I think the problem is: the mash tun. The false bottom creates 2 gallons of dead space, so to get the water/grist ratio of 1.25 I need to add 6.375 gallons of strike water to the tun. 2 gallons of that water sits at the bottom of the tun throughout the mash. I stir occasionally throughout the mash. The other problem with 2 gals of dead space is that it only leaves me with a little less than 3 gallons to sparge.

I vorlauf ~2 gals of first runnings then a 40 minute sparge with a gravity sparge arm.

My concern is that with less than 3 gallons of sparge water, the grains aren't being properly rinsed.

In all, I start with 9 gals of water, 6.5 make it to the kettle and 5.25 to the fermenter.

Any and all comments welcome. Thanks!

EDIT: I have received some comments suggesting I get a dip tube. To be clear I have a dip tube - I am leaving very little wort in the mash tun. My problem is that I have two gallons of water sitting below the false bottom that doesn't come into contact with the grain.

This is the kettle: http://www.homebrewstuff.com/10-gallon-kettle-w-valve-thermometer.html
The legs on the FB are two inches tall and the pot is just under 18" wide, so {(pi*9^2*2)/231} = 2.2 gals

 

[lazarwolf]

I think you have figured out the problem. The numbers jive almost exactly. You arent really making 6.5 gallons of wort, you are making 8.5. I have a similar issue with my indoor set up. I loose a gallon of wort. So I have to add that to the batch calculations. Although, Ill admit I often take that gallon and use it to build up sours etc...

 

[AF1HomeBrew]

Do have a pump that can recirculate the mash? My Bru-Gear 20 gal. kettle has about the same dead space, but I recirculate throughout the mashing...

 

[BrewHark]

I am thinking about recirculating but wasn't sure if that would fully compensate for such a small amount of sparge water. Thoughts?

 

[chickypad]

Deadspace should be less of an issue with fly sparging than batch sparging, but I suppose you could have some higher gravity runnings trapped in the deadspace. Sounds like you need a diptube.

 

[ScrewyBrewer]

Wow. 20% dead space is a lot. When fly sparging with a 5 gallon cooler and a braided stainless steel grain filter there is like only a quart of dead space. After several more mashes you'll have the amount of grain dialed in to hit our OG, but it may require adding considerably more grain to your recipes.

 

[bkboiler]

that's a lot of dead space even for a 10 gallon kettle. Are you sure you measured correctly?
i use a 5 gallon cooler with a stainless braided sock instead of a false bottom and thought that this and the dead space were the cause of my efficiency issues, but within the last few brews I realized it was because I was draining the mash tun too quickly. once I finally began draining at slightly more than a trickle (first runnings takes 20 mins or so and 2nd runnings from batch sparging takes 20-25 mins). then my efficiency shot up to 75-80% instead of 55% where it used to be for a over a year. I always program Beersmith for 75% and then can top up with a tiny bit of water if I am more efficient.

 

[aprichman]

If you're leaving 2 gallons of wort in the mash tun you need to figure out a way to rig up a pickup tube.

 

[AF1HomeBrew]

If you're leaving 2 gallons of wort in the mash tun you need to figure out a way to rig up a pickup tube.

I think he does get the 2 gallons out, but that it's liquid that isn't coming in contact with the grain during mashing causing him not to get the efficiency... Recirculating should help him out.

 

[CA_Mouse]

I agree with chickypad, sounds like you need a pick up tube. My 16 gallon with false bottom would leave about 1.25 gallons so I got a short pick up tube and now it leaves less than .5 gallons. If you are pulling off the correct boil volume and leaving 2 gallons in the MT, than lazarwolf is correct in that you are leaving a lot of sugars in that 2 gallons of dead space.

 

[Qhrumphf]

Was gonna say it, but the rest already did, definitely need a dip tube. Not sure why anyone bothers with that design of false bottom (the kind that sits flat above the kettle bulkhead, yes?) without putting a diptube in. I got the cheap domed false bottom with an elbow in the middle that sits flat against the bottom of my cooler MLT (below the bulkhead) with some barbed fittings and high temp tubing between the false bottom elbow the ball valve bulkhead. My deadspace is usually only a quart or so, and because it's drawn from the very bottom by the nature of the design, it's only the tail end of runnings left behind.

The only flaw I see with my design (both cheap and effective) is that it's possible to disconnect the tubing between false bottom and bulkhead while stirring the mash. Only done it a couple times out of +100 batches through it though. But it's a major nuisance when it happens as I have to transfer the entire mash.

 

[AF1HomeBrew]

Was gonna say it, but the rest already did, definitely need a dip tube. Not sure why anyone bothers with that design of false bottom (the kind that sits flat above the kettle bulkhead, yes?) without putting a diptube in. I got the cheap domed false bottom with an elbow in the middle that sits flat against the bottom of my cooler MLT (below the bulkhead) with some barbed fittings and high temp tubing between the false bottom elbow the ball valve bulkhead. My deadspace is usually only a quart or so, and because it's drawn from the very bottom by the nature of the design, it's only the tail end of runnings left behind.

The only flaw I see with my design (both cheap and effective) is that it's possible to disconnect the tubing between false bottom and bulkhead while stirring the mash. Only done it a couple times out of +100 batches through it though. But it's a major nuisance when it happens as I have to transfer the entire mash.

Definitely necessary to use a dip tube... When a lot of us bought kettles from Bru-Gear... they didn't even supply one... I had to end up finding my own https://www.homebrewtalk.com/showpost.php?p=6570024&postcount=25. Not sure which kettle the OP bought on homebrewstuff.com

 

[BrewHark]

that's a lot of dead space even for a 10 gallon kettle. Are you sure you measured correctly?
i use a 5 gallon cooler with a stainless braided sock instead of a false bottom and thought that this and the dead space were the cause of my efficiency issues, but within the last few brews I realized it was because I was draining the mash tun too quickly. once I finally began draining at slightly more than a trickle (first runnings takes 20 mins or so and 2nd runnings from batch sparging takes 20-25 mins). then my efficiency shot up to 75-80% instead of 55% where it used to be for a over a year. I always program Beersmith for 75% and then can top up with a tiny bit of water if I am more efficient.

Positive. I sat the false bottom in place and poured in 2 gals of water before it came up to the screen.

 

[pricelessbrewing]

I would look into a dip tube or replace the false bottom. A 2 gallon dead space is going to reduce your mash efficiency quite a bit. My "typical" brew setup will lose about 13%mash efficiency with a 2 gallon dead space is no dead space.