New mash tun, super low efficiency, help needed

[trussyd]

Hi All,

I got a new esky for Christmas to use as a mash tun and had my first run with it today. I ended up with an efficiency of about 65% which is way below what I used to get (sometimes nudging 80%).

• 
  My old system was a small esky with a manifold at the bottom to drain. I used to batch sparge due to the small size of the esky.
  
• 
  With shiny new 55l job I was able to have a go at continuous sparging for the first time.
  
• 
  Instead of fitting a new manifold I just used a grain bag (cheaper and easier)
  
• 
  6kg of pale malt mashed in 18L of water and sparged with another 18L to make 30L into the kettle.
  
• 
  30L of 1.023 went into the kettle at 62C. This equates to about 1.040
  
• 
  While I didnt measure flow rate while sparging it was probably around 2L/min.
  

My first suspicions were aroused when I took a SG measurement of the final runnings just as the kettle was nearly full. It was a corrected SG of 1.049! I was expecting somewhere around 1.004. It was down to a trickle so the wort coming out would have been in contact with the grain bed for a long time.

Now over to you AHB world. What do you think I've done wrong? Has anyone had success using a grain bag instead of a false bottom / drainage manifold? Do you think my flow rate was too high? Or is there something entirely different going on?

On a related note: how do all the BIABers out there get their grain bag clean after each brew?!?

Thanks,

 

[twizt1d]

sounds like channeling, you are probably going to need a manifold/falsie to fly sparge
when im fly sparging its somewhere around 1L/min, slower the better (within reason)

besides if you are getting good efficiency with batch sparging, stick with it


i used to turn the bag inside out and hose as much off as i could be bothered
hang it on the clothes line to dry then shake the rest of the crap off it
doesnt have to be spotless, just dont leave it damp for too long

 

[philmud]

Very quickly re: BIAB bag cleaning. I turn it inside out and blast it with the hose. Then dry it and brush whatever is left off.

Edit: beaten by Tone...

 

[malt_shovel]

The surface area you are trying to drain from is the cross sectional area of the hole in the mash tun. Basically as has been suggested earlier you are bypassing sugar laden liquor in the bulk of the tun. Either batch sparge (recommend until a manifold / false bottom is available) or treat like BIAB and use the entire liquor volume to infuse. Once you have a manifold worked out give fly sparging another try. Keep the flow rate down and you will be getting better lautering efficiency.