Stuck Mash And False Bottom

[benno1973]

Sorry about the long post - I'm having a bit of an issue with the draining of my mash tun. Every time (without fail) I get a stuck mash.

First some notes on my system. I have a 40L urn that drains into a gatorade cooler with a stainless steel false bottom. The false bottom is connected to a weldless fitting with a ball valve, and this drains (via gravity through a hose) to my boil kettle. If you've got trouble visualising, I've included a couple of piccies.



I hear lots of people complain of stuck sparges due to the fineness of their grind, however I don't think that this is the issue for me. Each mash goes the same way - I dough in and give it a gentle stir, let it sit for the required time, and then go to drain off. When I open the ball valve slightly, I either get one of 2 situations:

1. Nothing comes out. No matter how much I open the valve from there, nothing happens.
2. I get a slow steady stream of wort which I drain until it's clear into a jug. As soon as I move the hose into the boil kettle to continue draining, the flow stops, and no matter how much I open the valve, nothing happens.

After this, I have to resort to pulling down the mash tun, bailing everything out into a bucket, cleaning the mash tun, and pouring the grains/liquid back in. After this, everything flows smoothly, but by this stage my mash temps have dropped significantly and it's far from ideal.

So what I've considered so far:

1. Stuck mash due to the grind? I don't think so. I've tried a really coarse grind, and it didn't help, just reduced my efficiency. It also doesn't explain why, after bailing out and cleaning the mash tun, it all works fine.

2. Air pockets in the hose? I noticed (when doing a test run without grains) that when I filled my mash tun with water, there were air pockets trapped in the tubing leading from the false bottom to the ball valve. Different combinations of opening the ball valve and moving the tubing would force the air pockets out into the grain bed, presumably floating the false bottom and allowing grains underneath.

To test this theory, my last mash I bled all the air pockets from the lines before doughing in and primed the hoses with water. This didn't fix anything - the priming water drained out but the mash stuck fast, and again I had to bail everything out.

3. You'll notice at the bottom of the gatorade coolers, there's a raised bump right in the centre, presumably from the extrusion of the plastic lining.

I also noticed with my last mash, that when I went to bleed the air from the lines (at this point there was just hot water in there, no grains) that even the water wouldn't flow - not a drop. I realised that when you fill these coolers with hot water, the plastic lining expands which bows the base slightly convex. This raises the small bump on the base which then comes into contact with the inlet of the false bottom, essentially blocking it off. I pulled the false bottom out and raised the inlet higher and this seemed to solve the problem, but when it came time to run the mash off, nothing came out (again).

So I'm just looking for any other ideas, or anyone who might have had a similar experience. I tend to think that it isn't to do with the grind, but I'm prepared to try some 'shop-ground' grain if all else fails. My thoughts were either that grain gets under the false bottom (sometimes this appears to be the case, but its hard to tell) or that air pockets were preventing the liquid from drawing properly. Keep in mind that, for some reason, bailing out the mash tun, cleaning it, and then refilling it seems to work fine, so possibly the temperature of the mash drops during this time changing *something* and allowing the mash to run freely.

Any troubleshooting advice welcome!!

 

[warrenlw63]

KS

My guess would be the bit of plastic tubing you're using to join your FB to the bulkhead. Probably gets banged around when you're mashing in and lets bits of grain under your FB. Either that or a combo of the heat and weight of the mash pressing down too hard and squashing said tube.

You need to plumb the two together with some S/S or copper pipe. It's not too difficult to do.

Edit: pic added to better emphasise what I'm on about.

Warren -

 

[KHB]

My first thought is the bit of plastic hose is buckling under heat and not staying open, i would replace with copper pipe.

M2c

Warren beat me to it!!

Damn

 

[brendo]

that or replace the vinyl tubing with silicon hose (if you want something easier to remove) - it will resist the collapsing more (assuming this is the problem).

Cheers,

Brendo

 

[Sammus]

Maybe do your recirculation slower. If you do it to quick you can compact the grain bed, which I guess could hinder flow somewhat.

 

[Yorg]

It still doesn't entirely explain why it works when you restore it, but definitely replace the tube. I use silicon hose. I have also used plastic hose with a spiral of stainlesswire in it ( suction hose) that I got from a wine making shop.
The silicon hose slips on and off easily for cleaning.
Let us know how it goes.

 

[BennyBrewster]

+1 for the pvc tube collapsing.

Although you would have noticed it when you did a hot water test.

 

[niggles]

Yep, agree with the other guys... replace the pvc with something more resistant to collapsing.

I have a similar tun/fb, & ended up going with 10mm reinforced pvc hose (from bunnings). Thought about the copper, but the geometry of the setup (not much room between hosetails) make it a bit hard to install/disassemble/clean.



I use a slightly longer hose so it all fits nicely & is easy to disassemble/clean. Also, fit a couple hoseclamps so the hose doesn't pop off...
Works great, no stuck sparges, no probs with air pockets.

Cheers, Niggles.

 

[benno1973]

So the consensus seems to be replace the tubing... good idea!

The tubing is pretty flexible (I can squeeze it easily between my fingers even when it hasn't been heated), so there is some chance it is being crushed under the weight of the mash. Not sure why it resurrected itself when I bailed out the mash tun, but it could just be the change in temps. Actually, now I think about it, when I do drain the mash tun, it drains fast to start with and then slows *riiiiggghhhttt* down towards the end. Maybe spending an hour at mash temps is enough to collapse the tubing.

I've seen the reinforced PVC hose from Bunnings, so I'll get me some of that and test it out. I'll let you know how it goes, although my wife's just had a baby so it could be a few weeks before the next brew day!

Thanks for all the responses...

 

[niggles]

Yep, I'm guessing the progressive slowing of drainoff might be due to the compaction of the grain bed as it sucks down through the sparge? This might explain why it worked better after you bailed out the tun.

Oh, while you're at the hardware shop maybe grab a decent sized washer for the outside of the mash tun.... I have the rubbermaid/gatorade cooler as well, & a big washer makes it a little more solid & gives a much nicer joint (less flexy when using the tap etc).



BTW, with my setup (same cooler/FB) I've been getting pretty good mash efficiency (85-90%) extraction with a reasonably fine crush (1mm mill gap) & batch sparge in two equal volumes.

Cheers, Niggles.

 

[snoozer]

Hi all,
KS, it seems I have the exact same problem as u with the same rubbermaid, FB setup. Runs well into a jug during vorlauf but when I attch my silicon hose (about 1m long) to transfer into the kettle same thing happens! Starts of OK, but then slows right down eventually stopping with lots left to transfer. At first I thought I was opening the ballvalve too wide and running off too quickly resulting in a compacted grainbed. But I've tried varying the runoff rate (ballvalve wide open or nearly shut) with the same results, a transfer that stops midway with wort still above the grainbed! This only seems to happen when I connect the hose mind you, when I remove it and transfer all the wort with a jug it flows well until its complete. So the problem seems to be with the transfer hose and it doesn't matter how high I have the MT above the kettle, it will slow right down and stop. I'm using neoprene hose between the FB and outlet and its quite rigid. Can anyone offer any explanations as to why this happens? Its probably really simple...
cheers, snoozer

 

[benno1973]

Snoozer - what type of hose do you have between the false bottom and ball valve? Thinking about what the other guys said, if it's compressible, then the suction created by pulling the wort through will slowly compress the hose until you can't get any more through?

 

[snoozer]

Its a length of neoprene hosing I got from Craftbrewer,which is reasonably rigid. Is suction created when pulling the wort through? :unsure: I have the MT lid on loosly so air can enter on top and no vacuum forms as the tun emptys. Actually, I hope that is the problem 'cause then I can just replace the hose with pipe and problem solvered!

 

[Pumpy]

Yep there is only one way like Warren clamp it down with a bit of rigidity

Pumpy

 

[snoozer]

Thanks, and it will prolly solve the other problem I've had, grain getting under my FB due to it moving from an over zealous stir!. I'm guessing the FB wont be moving anywhere when attached via pipe to the bulkhead on the outlet.

 

[MHB]

If it isn't the hose, it might be the false bottom being forced down onto that bottom of the tun.
As the wort is drained more and more weight is applied to the false bottom, I have taken to putting a couple of cuts with an angle grinder in the bottom nut of the elbow, so that wort can flow in even if the face of the nut meets the floor.
That bump in the bottom might be exacerbating the problem.

Quick test
Put 5-10 L of water in the tun, open the tap, press down on the top of the elbow check the flow.
Good luck.

MHB

 

[Yorg]

Thanks, and it will prolly solve the other problem I've had, grain getting under my FB due to it moving from an over zealous stir!. I'm guessing the FB wont be moving anywhere when attached via pipe to the bulkhead on the outlet.

How's it gone?
Summarising above, its either:
1 Hose constriction
2 Grain compaction upon suction or settling
3 Blocking due to raised bit on the bottom.

Re 2: Are you crushing very fine, generating lots of fines that sludge your false bottom?

 

[snoozer]

How's it gone?
Summarising above, its either:
1 Hose constriction
2 Grain compaction upon suction or settling
3 Blocking due to raised bit on the bottom.

Re 2: Are you crushing very fine, generating lots of fines that sludge your false bottom?

Dunno yet, won't be brewing til next weekend. I'm guessing it's the hose being crushed under the weight of the mash. I may avoid the problem altogether anyway 'cause a larger mash tun is on the cards. A keg setup like pumpy's insulated with armaflex, I already have the FB, it fits the rubbermaid so it should fit a keg right? Incidentally, pumpy where did u get the stainless fittings & pipe connecting the FB to the outlet?
Oh, grain was precrushed by craftbrewer btw

 

[Ross]

Hi all,
KS, it seems I have the exact same problem as u with the same rubbermaid, FB setup. Runs well into a jug during vorlauf but when I attch my silicon hose (about 1m long) to transfer into the kettle same thing happens! Starts of OK, but then slows right down eventually stopping with lots left to transfer. At first I thought I was opening the ballvalve too wide and running off too quickly resulting in a compacted grainbed. But I've tried varying the runoff rate (ballvalve wide open or nearly shut) with the same results, a transfer that stops midway with wort still above the grainbed! This only seems to happen when I connect the hose mind you, when I remove it and transfer all the wort with a jug it flows well until its complete. So the problem seems to be with the transfer hose and it doesn't matter how high I have the MT above the kettle, it will slow right down and stop. I'm using neoprene hose between the FB and outlet and its quite rigid. Can anyone offer any explanations as to why this happens? Its probably really simple...
cheers, snoozer

Snoozer & most likely KS,

It's not the weight of the grain collapsing the tube, it's the suction created by the transfer hose causing the hot tube inside the mash tun to collapse. This is why it's fine with just the tap open (worts being pushed out, not sucked) & fine once the mash has cooled a little (tube in mash is becoming a little more rigid).
If this is not the problem, it's as MHB pointed out earlier, the bottom sucking on to the false bottom, because of pretty much the same senario as I just explained.

Good luck guys, shouldn't be hard to fix.

Cheers Ross

 

[Pumpy]

Dunno yet, won't be brewing til next weekend. I'm guessing it's the hose being crushed under the weight of the mash. I may avoid the problem altogether anyway 'cause a larger mash tun is on the cards. A keg setup like pumpy's insulated with armaflex, I already have the FB, it fits the rubbermaid so it should fit a keg right? Incidentally, pumpy where did u get the stainless fittings & pipe connecting the FB to the outlet?
Oh, grain was precrushed by craftbrewer btw

Snoozer,

The 1/2 BSP SS compression fittings are from Pirtek they are a a bit exxy but it solved my problem ,I have a 1/2 " BSP spigot welded in the side of my tun the pipethe pipe was from an old siphon I never used so put to good use

I have a 12" FB from CB but I have to support it under to stop the pump sucking it down ,I think the 9" FB may be better
(If you are just draining by gravity you should be OK)

I have been through lots of different FB but this is the trouble free version .

The FB is part of some other things I do to get I get 85% efficiency


Pumpy