BIAB bag getting sucked down to false bottom

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Rob2010SS

Rob2010SS

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Hi everyone. I've been using a brew bag in my MT on my Spike Trio + system for years now. I recently got a new Wilser bag as I ripped a hole in my last one. For me, the main benefit of the bag is easy removal of the grains from the MT. Instead of scooping the grains out, where it's almost guaranteed that you'll drop some when scooping out of the kettle, it's just one easy lift out of the kettle and into a bucket. Added benefit is it works as a filter.

However, since I got the new bag, I've had a problem with the pump sucking the bag down to the false bottom. This causes flow issues and actually is enough of an issue to stop the pump. I have to go and lift up the bag and I can feel AND hear it "pop" off of the false bottom. Once I do that, flow is restored and the pump continues working. Just brewed an Imperial Stout this weekend and ran into this again. It finally stopped doing it right around the 45-50 minute mark but prior to that, I was having to mess with the bag every 5 min or so.

I've seen some posts where other people have corrected this using a combination of rope/bungee cords and carabiners to tie around the bag and keep it from getting pulled down. However, my bag doesn't have multiple strap handles like those do. Besides eliminating the bag from the MT, anyone have any thoughts for solutions to this?
 
Sounds like the new bag is much finer than the last one? This would be the expected behavior... Assuming of course your mash didn't change i.e. reducing rice hulls, grinding finer, and so on. Or that you are running the pump faster (more flow through a valve) or you got a new pump. You probably already thought of these things.

That said, I think the Wilsers are all the same so that sort of doesn't really make sense. I don't have any issues with my Wilser bag but that probably doesn't help much.
 
tracer bullet said:
Sounds like the new bag is much finer than the last one? This would be the expected behavior... Assuming of course your mash didn't change i.e. reducing rice hulls, grinding finer, and so on. Or that you are running the pump faster (more flow through a valve) or you got a new pump. You probably already thought of these things.

That said, I think the Wilsers are all the same so that sort of doesn't really make sense. I don't have any issues with my Wilser bag but that probably doesn't help much.
Click to expand...
I wondered if something changed with the bag as well. I haven't reached out to him yet. Mash hasn't changed. I did have these grains milled twice just because it was an imperial stout, but I did not do that on the last brew which was an Amber ale at 1.35 qt/lb and I still ran into the issue.

Pump is trying to run at the same speed it always has - wide open.

Pump is the same pump.

If I could get the bag to stay off of the false bottom, I think it would solve it, but short of standing on a stool and manually pulling on the sides of the bag for the 60 min, not sure how to do that... yet.
 
how big is your pump? I use a Wilser but my pump is very tiny. BIAB is a fine crush which slows down flow a lot.
 
odie said:
how big is your pump? I use a Wilser but my pump is very tiny. BIAB is a fine crush which slows down flow a lot.
Click to expand...

As far as I know, nothing crazy for a pump. Standard pump that comes from Spike on their systems. Here's the info on it...

1635781614664.png
 
that's actually a pretty big pump on a home brewing scale IMO. You only need a slow flow for recirc. I use a little 12v pump I got on ebay that I power with a small transformer. I still have to use a mechanical outlet timer to cycle it on/off every 30 min since it can still out run the bag. Cost about 10 bucks. rated for 100'C so works fine for hot mash. Sorry, it's the best pic I have.

IMG_0426.JPG
 
^^^ Tend to agree, maybe simply reduce the flow rate. Maybe the new bag was somehow enough of a difference and you were already on the edge.

There could be a different change that happened, or issue, but if you run full bore then I'd add a valve and modulate it a little. Full could be a LOT.
 
odie said:
that's actually a pretty big pump on a home brewing scale IMO. You only need a slow flow for recirc. I use a little 12v pump I got on ebay that I power with a small transformer. I still have to use a mechanical outlet timer to cycle it on/off every 30 min since it can still out run the bag. Cost about 10 bucks. rated for 100'C so works fine for hot mash. Sorry, it's the best pic I have.

View attachment 747587
Click to expand...

So when I initially got this setup from Spike, I was running the pumps at a slow rate but I was seeing a huge temperature discrepancy between the top of the grain bed and the bottom where it was being pulled for recirculation. I contacted Spike on how to address that and they said to run the pumps full bore. Since then, it's been much better. I've been doing it that way for a long time with no issue until this new bag.

I wonder if just adding rice hulls to every recipe will help?
 
It should help, yes, a little more flow ability down the hull openings. It's a common thing to prevent stuck mashes which might be basically what you have.

Maybe ask Wilser if the bag changed, maybe the micron spacing got tighter? It's of course just one of many factors.

Might consider stirring a few times as well during the mash, and then skipping the last 10 - 15 minutes of you consider the reflow there to more or less be a vorlauf.

It's ugly and mroe money but maybe insulate the mash tun so you can get away with a slower flow rate. And simply play with the rate, maybe something between the old rate and full bore keeps it pretty even?
 
When I built my system I had the same thing happen, I ordered a 400 micron bag from The Brewbag replacing my 200 micron bag and throttled my flow down. I crush my grain really fine and have only had a problem when using a lot of flaked grains.
 
When mashing, I crush my grain using a .030 mill gap, typically using a 1.90 Qt/Lb (3.96 L/Kg) mash thickness, and throttle the flow rate down while stirring the mash frequently.
 
Rob2010SS said:
I was running the pumps at a slow rate but I was seeing a huge temperature discrepancy between the top of the grain bed and the bottom
Click to expand...
Put some good insulation around the kettle to reduce heat loss. Also around the return pipe.

The other thing to keep an eye on is the temp of the wort underneath the false bottom (where the elements are). You don't want the temp to be too high, denaturing enzymes prematurely.
 
tracer bullet said:
^^^ Tend to agree, maybe simply reduce the flow rate. Maybe the new bag was somehow enough of a difference and you were already on the edge.

There could be a different change that happened, or issue, but if you run full bore then I'd add a valve and modulate it a little. Full could be a LOT.
Click to expand...
That looks like a Chugger pump, same specs too. But my chuggers dont have the protrusion on the motor. Is that where the speed control is?
They (chugger) advise a ball valve on the output to control flow.
It is a magnetic drive so even dead-heading it shouldn't be a problem.
I use one for recirculating the mash and transfers.
 
Last edited:
Rob2010SS said:
This is pretty good. I like this, not terribly expensive. Might try the tube idea on the bottom first to see how it goes and then go this route if that doesn't work.
Click to expand...
To minimize dead space under the FB, I rigged it so the FB is under the pickup tube in my Spike 10 gallon MT. Had to remove part of the screen and it takes a little bit of finessing to install and remove but this has been working great for me.
3F82A41A-23C4-4740-B1C8-2790937A054E.jpeg
 
IslandLizard said:
Put some good insulation around the kettle to reduce heat loss. Also around the return pipe.

The other thing to keep an eye on is the temp of the wort underneath the false bottom (where the elements are). You don't want the temp to be too high, denaturing enzymes prematurely.
Click to expand...

I don't have any elements in the MT. It's a HERMS system.
 
yorkeken said:
To minimize dead space under the FB, I rigged it so the FB is under the pickup tube in my Spike 10 gallon MT. Had to remove part of the screen and it takes a little bit of finessing to install and remove but this has been working great for me.View attachment 747645
Click to expand...
So I already have a false bottom that I'm using. Is there any issue in using this BIAB false bottom on top of my pre-existing false bottom? The idea is to keep the bag off of my current false bottom and this would be perfect, but want to make sure I'm not missing any negative aspects of doing this.
 
Rob2010SS said:
So I already have a false bottom that I'm using. Is there any issue in using this BIAB false bottom on top of my pre-existing false bottom? The idea is to keep the bag off of my current false bottom and this would be perfect,
Click to expand...
You don't want too much space underneath the false bottom assembly, adding a 2nd one increases that space.

I think the issue in your current system is that when the mesh bag is resting upon the false bottom, it's not permeable enough. The much coarser grate of the NorCal false bottom may help alleviate that. Or not, the bag's finer mesh being the restriction.

But reducing the flow rate may simply solve the problem, without resorting to a coarser grate.
Have you measured the actual flow rate?
 
It's all about flow rate. Nothing else. If your pump exceeds the natural flow rate of your set up then you will get stuck. You can't push/pump/suck it through...it has to flow naturally.

Crush, bag mesh and surface area are the 3 things you need to look at. 3 is the number and the number is 3 "Monty Python"

1. Crush: a finer crush slow the natural flow rate. Improved conversion but reduce circulation.
2. Bag mess: smaller micron will slow the flow rate.
3. Surface area: how much of the bag's bottom is exposed, ie not touching AYTHING? Anything the bottom of the bag is touching or resting on will stop the flow. A false bottom blocks the bag any place it touches. The more gaps or open space the FB provides the better the flow. A steamer basket has only a few holes to allow flow and a lot of solid bottom area, so a steamer rack or something holds the bag off a little, providing more exposed surface area to flow.

All three affect flow rate. Match your pump to that flow rate. Either improve any/all of those 3 to match the pump. Or reduce the pump to match the 3 flow limitations. Do both until they are in equilibrium.

Better, have the natural flow rate exceed the pump. I think most pumps people are using are over sized for the need.
 
odie said:
It's all about flow rate. Nothing else. If your pump exceeds the natural flow rate of your set up then you will get stuck. You can't push/pump/suck it through...it has to flow naturally.

... A false bottom blocks the bag any place it touches. The more gaps or open space the FB provides the better the flow. A steamer basket has only a few holes to allow flow and a lot of solid bottom area, so a steamer rack or something holds the bag off a little, providing more exposed surface area to flow.
Click to expand...

That's what I like about the pic Yorkeken posted.
That rack looks like it would work well with a bag.

My false bottom is the standard convex disk full of holes with plenty of solid area to cause problems for a bag (which I don't use).
 
Rob2010SS said:
Hi everyone. I've been using a brew bag in my MT on my Spike Trio + system for years now. I recently got a new Wilser bag as I ripped a hole in my last one. For me, the main benefit of the bag is easy removal of the grains from the MT. Instead of scooping the grains out, where it's almost guaranteed that you'll drop some when scooping out of the kettle, it's just one easy lift out of the kettle and into a bucket. Added benefit is it works as a filter.

However, since I got the new bag, I've had a problem with the pump sucking the bag down to the false bottom. This causes flow issues and actually is enough of an issue to stop the pump. I have to go and lift up the bag and I can feel AND hear it "pop" off of the false bottom. Once I do that, flow is restored and the pump continues working. Just brewed an Imperial Stout this weekend and ran into this again. It finally stopped doing it right around the 45-50 minute mark but prior to that, I was having to mess with the bag every 5 min or so.

I've seen some posts where other people have corrected this using a combination of rope/bungee cords and carabiners to tie around the bag and keep it from getting pulled down. However, my bag doesn't have multiple strap handles like those do. Besides eliminating the bag from the MT, anyone have any thoughts for solutions to this?
Click to expand...
Why not just skip the MT and use the BIAB in the kettle? BIAB cuts out the need for a MT. Or am I missing something?
 
PCABrewing said:
My false bottom is the standard convex disk full of holes with plenty of solid area to cause problems for a bag (which I don't use).
Click to expand...
get what is called a "bakers rack" or "cake cooling rack". They are typically a very open wire mesh grid with like 1/2" spacing. Almost "invisible".
 
IslandLizard said:
You don't want too much space underneath the false bottom assembly, adding a 2nd one increases that space.

I think the issue in your current system is that when the mesh bag is resting upon the false bottom, it's not permeable enough. The much coarser grate of the NorCal false bottom may help alleviate that. Or not, the bag's finer mesh being the restriction.

But reducing the flow rate may simply solve the problem, without resorting to a coarser grate.
Have you measured the actual flow rate?
Click to expand...
I have not measured the actual flow rate of the pump. Not even sure how I'd do that, other than a flow meter which I don't have or collecting wort for a measured period of time...
 
odie said:
It's all about flow rate. Nothing else. If your pump exceeds the natural flow rate of your set up then you will get stuck. You can't push/pump/suck it through...it has to flow naturally.

Crush, bag mesh and surface area are the 3 things you need to look at. 3 is the number and the number is 3 "Monty Python"

1. Crush: a finer crush slow the natural flow rate. Improved conversion but reduce circulation.
2. Bag mess: smaller micron will slow the flow rate.
3. Surface area: how much of the bag's bottom is exposed, ie not touching AYTHING? Anything the bottom of the bag is touching or resting on will stop the flow. A false bottom blocks the bag any place it touches. The more gaps or open space the FB provides the better the flow. A steamer basket has only a few holes to allow flow and a lot of solid bottom area, so a steamer rack or something holds the bag off a little, providing more exposed surface area to flow.

All three affect flow rate. Match your pump to that flow rate. Either improve any/all of those 3 to match the pump. Or reduce the pump to match the 3 flow limitations. Do both until they are in equilibrium.

Better, have the natural flow rate exceed the pump. I think most pumps people are using are over sized for the need.
Click to expand...
Ok, so if I took @yorkeken advice and just swapped my false bottom for that BIAB false bottom, that may actually help as well based on your number 3.

1635890441258.png


As you can see, there's a lot of surface area on that false bottom where when the bag is in contact, it could block the flow. By giving more room for liquid to flow, may help my issue. That in combination with reducing flow a bit, if need be.
 
I like that grated thing better. It'll do the job and have like 0 restrictions. The one you linked would be better than what you have perhaps, but - why not go for it?

Either way though, you're on the right track. Reduce the amount of stuff impeding the flow.

For the flow rate it's easy, next time you have a pot filled with water connected to your pump, maybe for cleaning or before you get it to strike temp, move it into another one with the pump and 1) count how long (time) it takes to 2) move X (volume) amount of water. 3 gallons in 30 seconds or something like that (which would of course be 6 gallons / minute). The math for flow rate will fall right out of that. It's also probably published, most companies use it for their advertising.
 
Rob2010SS said:
So I already have a false bottom that I'm using. Is there any issue in using this BIAB false bottom on top of my pre-existing false bottom? The idea is to keep the bag off of my current false bottom and this would be perfect, but want to make sure I'm not missing any negative aspects of doing this.
Click to expand...

Yes. A HUGE difference. Picture it like this... once you build up some suction under your false bottom, the bag gets pulled down hard to the false bottom. Now the only place the bag is able to drain is the spaces directly over the cut slots. When you switch to my coarse wire mesh false bottom, you get about 95% open area so you'll drain through almost the entire diameter.
 
Bobby_M said:
Yes. A HUGE difference. Picture it like this... once you build up some suction under your false bottom, the bag gets pulled down hard to the false bottom. Now the only place the bag is able to drain is the spaces directly over the cut slots. When you switch to my coarse wire mesh false bottom, you get about 95% open area so you'll drain through almost the entire diameter.
Click to expand...
^^This is some DEEP TRUTH^^

Ain't no false bottom
Like a BH false bottom
Cuz a BH false bottom is
PERMEABLE.
 
Rob2010SS said:
Ok, so if I took @yorkeken advice and just swapped my false bottom for that BIAB false bottom, that may actually help as well based on your number 3.

View attachment 747660

As you can see, there's a lot of surface area on that false bottom where when the bag is in contact, it could block the flow. By giving more room for liquid to flow, may help my issue. That in combination with reducing flow a bit, if need be.
Click to expand...
You want something that looks like post #23. that FB you have looks like a manhole cover...
 
You don't have to measure your flow rate...you just need to observe that the bag is draining faster than the pump is pumping...

watch your sight tube as the pump is running...if the level starts dropping then you know your pump is out running the bag flow.

If you don't have a sight tube, watch the wort level inside the bag...if it's going up then the bag is filling up faster than it can drain.

mark the starting level before running the pump. This is your base line. Once the pump is running it should not change unless you have a "problem" like too much pump or too little flow.
 

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