Pump Sucking Air During Mash

[BadNewsBrewery]

So I find myself in a bit of a pickle... I run a full electric HERMS setup, and use the standard 10 gallon igloo cooler w/ NorCal - jBird fals bottom in my mash tun. Calculating for the deadspace beneath the FB, I still end up mashing slightly thin to try and accomodate the flow through the HERMS coil.

Here's the issue I've been having - unless I run my HERMS pump (a Chugger) at 1/4 to 1/8 open on the discharge valve, I wind up sucking air into the system somehow. I have made entirely sure that all the fittings are tight and nothing leaks water anywhere, but after a period of time with the pump running I can see air in the line running from the MLT to the pump. If I kill the pump power and let the air run back into the MLT, I get quite a few large bubbles. Even after getting the entire system fully clear of air, if I run it again for a while, it starts getting air in the line.

Now from a logical standpoint, it seems only one of 2 things can be happening. 1 - the FB is causing such a restriction that cavitation is occuring within the line somewhere. This is highly unlikely, as such low pressure would cause other issues, and the air pocket wouldn't sustain in such large volumes. 2 - the FB is causing such a restriction that the pump is somehow causing one of the fittings to leak air, but only under the low-pressure scenario. Under normal operation, there's not enough of a vaccum to cause a leak to appear.

Otherse with a similar setup have claimed the ability to run their pump full-bore. Where would you focus your efforts? Rice-hulls to help keep the FB from getting jammed up? Tripple check all the valves and fittings? Devise some sort of system to stir / scrape the FB to keep it free and clear? Get a new FB? I thought the NorCal FB was suppose to be the bee's knees... I don't mill my own grains, but I've had this problem on multiple occasions with multiple LHBS / mill combos.

Thanks for the help,
-Kevin

 

[acidrain]

I would start by experimenting with water... FB out, water in the MLT and then start the circulation.
Put your finger over the pick-up port to see if you can re-create the issue.
If you can, then you should be able to figure out how it's getting air in the line.
You are right, there is no way a chugger can pull a vacuum.
A picture of your FB/pick up tube arrangement might help.

 

[eastoak]

i've recently had the same problem so i took out the FB and re-tightened the dip tube. i also took the (march) pump head off and found the thrust washer on the impeller shaft worn down to almost nothing. we'll see if anything changes this saturday when i brew.

 

[indianajns]

I know this may be a dumb question but I will ask it just in case. Do you wait 15 minutes after you dough-in before starting your recirculation? I have a similar setup and would constantly get a stuck mash as I would start my recirc as soon as the grain hit the water and the dough balls were gone. After waiting 15 minutes for everything to settle I rarley get a stuck mash unless I have a high wheat content and then I use rice hulls.

 

[eastoak]

i do wait for the grain to soak for 10 min. as long as i'm recirculating i don't have a problem but when disconnect the recirculating hose and put it over in the brew kettle i start getting the bubbles in the hose and the flow may slow way down. if i plug the hose back into the mash recirculating arm it behaves normally. most times it starts to flow into the boil kettle normally after connecting and disconnecting to the mash tun.

 

[wilconrad]

I have had the same issue with my setup on occasion and it appears to be related to a partially-stuck mash. If I give the mash a stir, that usually clears it up and it doesn't come back for the rest of the mash. If I'm brewing with wheat, rice hulls are a must to keep things flowing. I have a chugger center inlet pump and run it full open for the entirety of the mash.

 

[BadNewsBrewery]

I typically don't wait any period of time after dough-in. Break up the clumps, get everything settled, start pumping through the HERMS. I'll give that a shot next time.

I also posted this over in the electric brewing page as many people over there have similar setups to what I use, and it seems that a regimented and deliberate check of all fittings and connections is the way to go. I'll fill with water, and try to plug it up in some places to see if I can recreate the issue. No dip-tube to worry about, the outlet of the MT is below the FB, so I just pull straight from there.

Thanks for the tips!
-Kevin

 

[jsmcclure]

I had the same problem when I switched to the Chugger. It pulls really hard. I switched to a stainless gate valve to get better control of the flow. I keep it really clamped down for the first few minutes then gradually increase my flowrate. It never gets anywhere near wide open but the flow is plenty to make temperature control easy and maintain circulation. It really did the trick for me.


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[Rivenin]

i've recently had the same problem so i took out the FB and re-tightened the dip tube.

had the same problem, and that was the culprit... i didn't notice till one day i for some reason touched the dip tube in the HLT and the compression nut moved just a hair. was about a 1/2 turn from being tight or so. made all the difference, no more bubbles!

 

[eastoak]

had the same problem, and that was the culprit... i didn't notice till one day i for some reason touched the dip tube in the HLT and the compression nut moved just a hair. was about a 1/2 turn from being tight or so. made all the difference, no more bubbles!

i'm recirculating right now after tightening everything up and installing a new thrust washer, no bubbles. when i switch the hose over to the boil kettle we'll see if i have the same problem as before, i don't think it will happen.

 

[BadNewsBrewery]

The only place I could imagine a leak is either at the bulkhead fitting through the plastic side of the cooler (likely) or at the cam-lock fitting itself (less likely). I'll go through and torque the hell out of everything and give it a shot. Haven't had much of a chance to troubleshoot it as I've been pretty busy, but this week is looking good.

 

[eastoak]

i did not have any issues at all while brewing this weekend, i think the loose dip tube fitting was the problem in my case.

 

[BadNewsBrewery]

So I tightened all the fittings, filled the MLT with some water, hooked up the hoses, fired up the pump, and did my best to restrict the flow and create suction on the pump intake side. I even 'pulsed' my finger over the opening, causing the hose to jump about from the pressure changes.

In no way was I able to recreate the issue, and gave up after about 10 minutes of trying and my arm going numb... Which led to a few possible conclusions.

1 - The water was cold (48*), normally the wort is 100+* hotter - perhaps the heat is causing the fittings to flex or expand, and I can't recreate the scenario.
2 - It does have something to do with the FB, and I wasn't able to recreate the issue.
3 - By tightening the fittings I fixed it and the problem is solved.

I'm hoping for #3...

One question though - for those using a similar setup with a bulkhead fitting in your MLT (I don't use a dip tube, but no matter), and then a valve, and then a camlock fitting - do you find that the whole assembly outside the MLT is fairly long and unsupported? I'm thinking about trying to come up with a way to build a little stand that will take some of the weight of the equipment (and hose when it's attached) off the bulkhead fitting that's squeezing against a relatively thin piece of plastic. That stress can't be good, and may be another cause of possible failure. Anyone build their own little support?

-Kevin

 

[kombat]

Isn't this precisely what a "grant" is used for? You run the wort from the MLT to the grant using nothing but gravity, which eliminates the suction effect on the outlet port of the MLT and prevents cavitation. Then the pump takes the wort from the outlet barb/valve of the grant and recirculates it back to the MLT. The pump is cycled either manually (by keeping an eye on the wort level in the grant) or with a float switch.

 

[BBL_Brewer]

Isn't this precisely what a "grant" is used for? You run the wort from the MLT to the grant using nothing but gravity, which eliminates the suction effect on the outlet port of the MLT and prevents cavitation. Then the pump takes the wort from the outlet barb/valve of the grant and recirculates it back to the MLT. The pump is cycled either manually (by keeping an eye on the wort level in the grant) or with a float switch.

Grants aren't meant to prevent pump cavitation, they are meant to prevent the grain bed from compacting which can cause a stuck mash. You could use a grant for HERMS, but you're going to loose more heat that way, it's a more complicated, expensive set up and it will limit your flow rate. If you're running a HERMS, you probably don't want to loose any more heat than you have to and probably don't want any added flow restrictions. I guess if you're getting stuck mashes right and left you have no choice, but I don't think too many people use a grant with HERMS.

 

[acidrain]

Many people including myself use pumps and hoses without grants. I'd say it's un-usual to use a grant, and normal not to use one.

Supporting your fittings sounds like a good idea.

 

[eastoak]

my mash tun is a keg so there are no support issues for the valves/fittings.

 

[helibrewer]

If you pull fluid from under your FB faster than it can flow through the grain bed you will start drawing air...which will also further compact your grain bed. A grant prevents suction from being pulled on a grain bed, I use a 2 Qt grant on my Cooler MLT (bottom draining, no spigot conversion).

 

[BadNewsBrewery]

If you pull fluid from under your FB faster than it can flow through the grain bed you will start drawing air...

Where might said air be drawing from? Are you suggesting that funnel or vortex might form through the grain bed? If the valves and fittings are air tight, then where would that air be originating? I don't think I follow your logic there.

 

[hunter306]

Out of curiosity and with little actual useful contribution to your problem, Are you using Rice Hulls during your recirc? I've taken to tossing them in every batch now.

Basically cheap insurance, and we haven't seen any trouble with getting nice recirc through the HERMS coil now. We even opened it up quicker last brew and got quite a decent flow going.

 

[BadNewsBrewery]

No hulls, but like you say - cheap insurance.

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[BadNewsBrewery]

Got a brew in yesterday, and I have to say, total success, but I threw the scientific method out the window so who knows what the exact fix was.

1 - Added a half pound of rice hulls to the mash. I added some early while heating the water / recirculating through the HERMS and a few got through and clogged my HERMS valve which killed me flow and had me totally worried until I diagnosed and fixed it. The majority were added to the grains and mixed in.

2 - I let it sit a while before starting up the HERMS, mainly because I was dealing with the clogged valve, so things had a little time to settle.

3 - I had tightened the fittings earlier.

I have to say, I was able to run the HERMS pump at full volume for the entire mash, no issues. Thanks for all your help, HBT!
-Kevin

 

[hunter306]

Glad to hear you had a successful mash. I was nervous the first mash-in after our issues, but haven't seen any trouble since.

Also, I still haven't tried to go full open on my valves since the incident. Did you ease them open, or did you just swing them right open at the start of your herms recirc?

 

[BadNewsBrewery]

I worked into full open, but maybe only over a period of 10-15 seconds.

 

[kiblerjd]

I know this is a super old post but I'm having the exact same issue and I'm completely stumped. My QD fittings are the CPC ones they have always worked great for me. To rule that out I got oversized o-rings and actually even removed the QD and replace it with a barb. No luck. It is the weirdest thing if I get past half open on my outlet valve it sucks so much air it binds the pump. I don't even understand where the air could be coming from but you can see it in the hose right where it comes out of the mash tun. This is the weirdest thing. If there isn't a fitting leak where the heck could air be coming from.

When my mash was done today I actually added water back into the grain bed and did a ton of experiments and it did it every single time. I'm losing my mind over here hahaha. I attached a picture of my setup. If anyone has advice I would greatly appreciate it. I don't mind using rice hulls if that could help but I still don't get where the friggin air is coming from!

 

[kiblerjd]

Figured I would follow up on my own reply to help anyone else that might stumble on this in the future. With everything else eliminated I did another batch and only changed two things. I loosened up my grain mill a bit (now at just a hair above 1.1mm) and added a half pound of rice hulls to the mash. Air bubble problem complete gone. Not only that but my entire system was much happier having that nice unrestricted flow. So my only guess is that the mash was so tight before the suction was actually pulling entrained air from the grains in the mash and that is what i was seeing. My pump was powerful enough to overcome the fact that i probably had a 95% stuck mash. What a difference those two changes made very happy now.

 

[Vale71]

There is no such thing as entrained air in the grain. Once you mash in any air will float to the top and be gone. Your system was most likely pulling so much negative pressure with the stuck mash condition that it was pulling air in from some connection. Fittings that are designed to seal with positive pressure often end up being leaky when pressure is applied in the opposite direction, i.e. from the outside to the inside instead of vice-versa.

 

[kiblerjd]

Sorry i guess i skipped two key pieces of information with that theory. The night before the second batch i did a wet test with just water on the system. I got the system running and literally plugged the suction of my mash tun with my finger and could not get air bubbles to draw in anywhere on any fitting, valve, connection, etc. I routed the hoses in several different ways and could not get a leak at vacuum or pressure.

Another key thing is that when i batch sparge i will drain the mash tun completely for the first runnings, then add the sparge water and recirculate, completely drain again, and repeat for a total of three times. Been doing it that way for a long time and I seem to get consistently high efficiency. I won't bore you with the other details but that method works very well for me and is 1000 times faster than fly sparging. So when I do it that way it certainly re-introduces air into the grain.

 

[odie]

your pump is too big...simple as that IMO. the pump you are using simply has a greater flow rate than the natural gravity flow of your mash.

switch to a smaller pump. You can't force the mash. That will just compact it more and exasperate your problem.

 

[kiblerjd]

Hey there thanks for the reply. I actually have this thing dialed in now. Just got done brewing could not have gone better. Once I got my mill adjusted, added the rice hulls, and took the time to figure out my flow rates these pumps are actually working great.

having said that part of getting this fixed involved adding some restrictions in the system to be able to control the flow better. You are right the pump is way more pump than I needed and before it was hard to adjust the flow. I went back to smaller tubing and smalle qd’s on that part of the system and it now works like a dream.

 

[day_trippr]

I have to say I'm surprised this system couldn't be easily managed using the properly placed ball valves on the pump outputs. I run a similar 3v2p single tier rig with a pair of 815PLs and control is never a problem - certainly don't need any added restriction beyond what the ball valves provide. All tubing is 1/2" Si and all camlock fittings are @Bobby_M's high-flow models...

Cheers!

 

[kiblerjd]

I'm surprised this system couldn't be easily managed using the properly placed ball valves on the pump outputs

Yeah I was surprised too! Because those pumps are so powerful tiny little changes with the pump outlet ball valve would cause huge changes in flow. I think it was just in that sweet spot on the ball valve where flow control just wasn't at its peak. Super happy now. I have to say too once I got the flow under control the rims system really started to get a lot happier too. I'll have to take an updated picture next time i'm brewing. I added a small sight glass to the outlet of the RIMS and ohh boy was that a great upgrade as well. I'm just super super happy with everything now this last brew day just felt like things were finally dialed in.

Also FWIW these chugger pumps are absolutely amazing. I think I did a separate post on this site, but now that i have even more time with them..... they are amazing. Far far better than the riptide but that is purely just my opinion so please don't get worked up if anyone is a die hard riptide fan haha.

 

[Hwk-I-St8]

Yeah I was surprised too! Because those pumps are so powerful tiny little changes with the pump outlet ball valve would cause huge changes in flow. I think it was just in that sweet spot on the ball valve where flow control just wasn't at its peak. Super happy now. I have to say too once I got the flow under control the rims system really started to get a lot happier too. I'll have to take an updated picture next time i'm brewing. I added a small sight glass to the outlet of the RIMS and ohh boy was that a great upgrade as well. I'm just super super happy with everything now this last brew day just felt like things were finally dialed in.

Also FWIW these chugger pumps are absolutely amazing. I think I did a separate post on this site, but now that i have even more time with them..... they are amazing. Far far better than the riptide but that is purely just my opinion so please don't get worked up if anyone is a die hard riptide fan haha.

What did you use for a sight glass?

 

[kiblerjd]

Ss Brewtech one. Small and decent price.