Sparge sticks in 5gal MLT but not in 10gal. Any ideas?

[QuaffableQuips]

Here's one for you. I've been mashing in a converted 10gal Home Depot cooler for several years now. I get consistently good brewhouse efficiency (70-80%) and haven't experienced a single stuck sparge, even with large percentages of wheat, rye, or oats. I batch sparge with this lauter screen from Bargain Fittings and a weldless bulkhead/valve kit from the same vendor. I couldn't be happier, except it doesn't maintain temperatures as well for small grain bills (<1.045ish) as for larger ones due to the headspace.

So, I decided to build a second MLT from a 5gal Home Depot cooler. I used exactly the same components as for the 10gal, except I had to shorten the kettle screen to make it fit in the cooler. I just snipped a couple of inches off the end and crimped it. Otherwise, it's the same setup as above, just smaller scale.

However, every time I've mashed in this smaller cooler, the sparge has either stuck, or the runoff has been exceptionally slow. I've eliminated just about every variable I can think of, and I still can't figure out what might be causing it. I can look straight down the barrel of the ball valve and see the lauter screen when the tun is empty. And the screen doesn't collapse at all under the weight of the grain. I've only been able to save my sparges by blowing into the silicone tubing and vorlaufing again. I may have to do this 4 or 5 times during the sparge.

Am I missing something? The only thing I can think of is maybe there's some relationship between crush size and tun geometry. But if the screen mesh spacing is the same, that doesn't seem like it should matter. I also thought about the height of the grain bed relative to the diameter of the vessel, but if that were the case shouldn't I get stuck sparges when I mash high gravity grists in the 10gal tun?

I'm at a loss. Any ideas? I can still mash in the larger MLT, so at this point I'm mostly trying to figure this out because I'm stubborn.

 

[zzARzz]

The only thing I could think of is maybe try a coarser grind the next time you use it and see if that solves the issue. The combination of the concentrated weight and a finer grind (assuming that's what you're doing, of course) may be what's causing the stuck sparges. Your efficiency may suffer a bit, but at least it will tell you if you need to go in a different direction or not.

 

[poislb]

I had the same problem, even used a false bottom. Maybe its the small cyl size of the cooler and the amount of grain weight or something preventing it from vourlouf. Didnt care to figure it out so up graded to a 10 gallon myself years ago.

 

[helibrewer]

I think it's the tall, narrow grain bed

 

[buzzno]

I mash in two 5gal round gott coolers but I don't have the tube screen like you have, I use a braid fashioned in a circle and I've never had a stuck sparge. It might be the tall narrow grain bed difference. I use rice hulls to help with drainage because I noticed it was slow when I first started using this system.

 

[TrubDog]

I have my own mill and I crush at .035 - lots of flour. I have two MTs, one 5 gal Rubbermaid and a larger rectangular one. I use a copper manifold in one and a cpvc in the other. Never had a stuck sparge, always a good flow. It's your setup.

 

[QuaffableQuips]

Thanks for the input. Coarsening my crush is probably the next thing to try. Maybe the dimensions of the narrower tun simply won't allow me to use the same crush I do on the larger setup, even though the filter screen is the same. I condition the malt prior to milling, so I get fairly intact husks, even with a relatively fine crush. Though I don't go as low as TrubDog, I'm only at 0.037. Just a little tighter than the factory setting (Barley Crusher).

I am interested in the manifold idea and have seen some good designs around here. CPVC is pretty cheap, so it might be would be worth a try. Particularly if it allows me to use the same crush for both tuns.

Thanks a lot for the feedback. Appreciated as always! I'll update here after I try some of these ideas.

 

[forstmeister]

Maybe just add a couple handfuls of rice hulls to the mash. It would be cheaper than losing efficiency to a coarser crush most likely.

 

[QuaffableQuips]

Maybe just add a couple handfuls of rice hulls to the mash. It would be cheaper than losing efficiency to a coarser crush most likely.

Thanks, I actually tried this a few batches ago when I made a dry stout with 20% flaked barley. Given my prior experiences and the large amount of sticky adjunct, I used half a pound of rice hulls, which is considerably more than I usually would use. Still stuck on me. Next time I'll try a full pound.