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Author: Subject: Water pumps for Distilation
Arcus
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[*] posted on 12-5-2021 at 11:07
Water pumps for Distilation


My water pump broke due to some fault, and I need to buy a new one. Do you know what sort of speed is best for general distillations? eBay sellers have many options: Everything from 180/h to 17000L/h. I thought if it was on the high side it could cause enough pressure to break the glass, but not enough and it wouldn't cool it enough.
Any help is appreciated, as I have not been able to find any useful answers.

[Edited on 12-5-2021 by Arcus]
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Oxy
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[*] posted on 12-5-2021 at 11:31


You want a pump which will pump the water to the condenser? I am using the cheapest one from hardware store which can pump few l/min.
You don't need enormous speed and pressure for coolant circulation.
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Fyndium
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[*] posted on 12-5-2021 at 12:18


I suggest using an industrial pressure washer for condenser.

No, really, even the cheapest aquarium or aquaponic pump is more than sufficient for any tabletop distillations. The head might be 30-50cm so the pump circuit must be primed by either lowering the condenser or raising the reservoir, but after that it keeps the water running.

For ejector aspirator pump, things are a bit different. You want at least 5bar pressure with at least 10L/min rated capacity. The ejector will throttle the flow to it's capacity.
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B(a)P
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[*] posted on 12-5-2021 at 13:36


I run a cheap pond pump. Don't worry too much about flow rate, just make sure the pump can achieve the head you need. Then to deal with the flow rate you can have a recirculation loop before your condenser with a valve on the line going to the condenser and one on the recirculation loop. You can then adjust your flow rate as needed.
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RustyShackleford
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[*] posted on 12-5-2021 at 15:11


I have been using these small 5 dollar 12VDC cube pumps for years. so far ive only replaced it once, but in retrospect it probably just had some gunk cought in the shaft.
The pump has good water pressure, its able to pump water from the floor to like 2m up without problems in performance. The flowrate is enough that ive never had issues, even with distillations so fast the stream was continuous.

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Sulaiman
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[*] posted on 12-5-2021 at 20:42


At home in UK I use small 5v or 12v d.c. water pumps,
here I'm using a 20W 220Vac submersible pump.

Flow rate is not a problem, very little flow is required.
(you can calculate the temperature rise of the water based on cooling power required (watts), flow rate and specific heat capacity of water)

Head (m or ft.) IS important;
When I use a small reservoir of water (with or without ice) on the bench there is no problem
but when I need to pump from low down (e.g. a bucket on the floor, or a swimming pool)
the available pressure is often not enough,
so, as mentioned above, I can prime the system and then it will keep working as the downwards flow 'sucks up' the upwards flow
- IF there are no air leaks.

The problem is that if for some reason the water circulation fails,
it is difficult to re-prime the system quickly enough to prevent gas/vapour escaping uncondensed.
Depending on what I'm distilling this could be just a nuisance,
or it could allow volatile/combustible/explosive or noxious gasses to escape in bulk.

I feel safer using 5v or 12v dc pumps,
but I do sometimes put my hands in the reservoir with a running 220Vac pump,
they don't kill fish so I expect I'll be ok.

P.S. foam/expanded polystyrene food boxes make excellent ice-water reservoirs




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Oxy
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[*] posted on 12-5-2021 at 23:41


Yes, when the pump is not so strong it may require to have the reservoir at the condenser's level. I keep the bucket with water next to my distillation setup.
The pump is running on 230V and on the beginning when I started using it I was very cautious when doing any manipulations while it was submerged. It serves me well however, no complains.

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Fyndium
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[*] posted on 13-5-2021 at 11:59


Very few people seem to understand the concept of "head". Sulaiman got it right on point.

I have survived with low head pumps, but the air bubbles are PITA. Air is dissolved in cold water, but as it heats, the air forms bubbles, which will eventually cause issues with circulation if the pump is not strong enough. The difference seldom has to be 100% of your true head, but something about 20-30% at max will be great, once you prime it. Using decent tubing and never letting reservoir drain completely will ease things.

I use reservoir that has a tap. I can easily drain off warm water and add more cold water without disturbing the circulation.
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