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Jun 08, 2022 View:

Wash transfer

I need to go from a fermenter to a centrifugal pump that feeds a continuous column.  The pump has a water hose connector for both input and output.  The fermenter uses a 2" Tri-clamp.  The input to the still is 3/8".

Would I be better off going into the pump with a 3/8" line from the fermenter or would a larger input hose be more efficient?

I have this working now going into the pump with a 3/8" connector but I am wondering if I gain any efficiency by going into the pump with a large supply hose.



Bigger supply hose is better. That way you are much less likely to cavitate the pump and get irregular output.


I agree with Jedd's comment above, I assume he means supply hose to the pump, after the pump it does not matter as long as you are getting enough flow.

I am using a variable rate diaphragm pump, when I was using a centrifugal the rate changed too much as the level in the supply tank dropped.

Also if there is any CO2 left in the feed a centrifugal will cavitate (foam around the impellor) very easily.



Thanks @Pete B  I'll keep an eye out for foam in the lines at the pump intake and exhaust.  

Any ideas on a small variable rate diaphragm pump if I need to change?  My feed rate is only 100 liters/hour.


26 gallons an hour is a tricky one.  For me, metering that little, 1/2 gallon a minute +- some for adjustability, feels like a displacement pump.   Any pump with 1.5-2" on the input is going to be too big unless throttled down pretty substantially.

Do you have air handy?  Why not try a small aodd/diaphragm pump?  Something on the smaller side, 3/8" to 1/2"?  The nice thing is that they dispense a specific amount per pulse.  You can count your pulses (like heart beat), and get a fairly good approximation of flow rate without needing flow meters, etc.

Small centrifugal pump with a 3 phase motor (a bit of an oxymoron) will let you dial it back a bit with a frequency drive, that'll let you dial your pump curve back enough that you can control it more easily with a valve.


@Silk City DistillersThe centrifugal I'm using a 1/10 hp 12 volt bilge pump and it seems to be working quite well.  I'm going to increase the intake to 5/8" stepping down from a 2" tri-clamp on a 500 gallon fermenter leaving the exhaust at 3/8" which is the intake on the still.  I do have air handy if I need to change things.  At this point it seems that I am able to control the flow pretty well with the valve on the still.  But, I have not done a full fermenter yet so I may still have issues that I am not aware of.


If anything the increased head pressure from the full fermenter would help prevent cavitation.  You might see a little variability in flow rate from start to finish, but probably minor.

I could probably send you a variable speed peristaltic to try out if you wanted to experiment with something different.  Also have a bunch of smaller centrifugals laying around.


Go with air power. It's super easy to set a rate with a pressure regulator. You can plumb the air pump way far away from where you work so you won't hear it. The fluid pumps themselves are generally pretty quiet. When I was doing sand blasting I setup the air pump on the other part of the building and put a large 100g receiver tank near where was working. I don't think you would need something that big but it would be a good idea to have something closer to the pump. It helps reduce cycling with the main pump, cools the air, and catches any fluid in the line. Also plumb in an on/off valve before the regulator so you can just turn that off and not mess with the regulator every time.

One thing you didn't mention - do you pump solids or not? I'm assuming with a 3/8 feed to the still you're not.

For non solids the Flojet G57 series might be just right for you depending on how low the flow rate is on the low side. It has 1/2" connections so you would only need a reducer on the output side. I wouldn't be concerned with the input side as your feed rate is really slow.

Reply:4 hours ago, Silk City Distillers said:
Reply:On 8/23/2021 at 7:54 PM, Thatch said:
Reply:On 8/23/2021 at 9:52 PM, Silk City Distillers said:
Reply:On 9/7/2021 at 8:34 AM, PeteB said: