Sciencemadness Discussion Board

Pump for recirculating aspirator?

monolithic - 5-3-2018 at 19:48

I'm looking to build a recirculating aspirator for vacuum filtration and vacuum distillation. My goal is 100mm Hg or under, which seems reasonable given the spec sheets of the Nalgene aspirator I want to use. I've done some research and came up with the following:

A submersible pump has far too much flow rate, which would dump heat into the water.
A fountain pump has reasonable flow rate but terrible pressure.
An RV water pump was seen in a NurdRage video, but many comments complained that typical performance was poor. There are also concerns about the longevity of the motor, since they are meant for intermittent use and not 100% duty cycle.
A used Procon pump, but 125gph and 175psi is way overkill and might blow up the aspirator.
A used 3/4 hp pool or spa pump, but I can't seem to find pressure ratings for most of these so I'm not sure.
A generic transfer pump/jet pump/utility pump like any of these, but I'm not sure how they would handle a 100% duty cycle for hours:
https://www.harborfreight.com/120-volt-portable-utility-pump... (1500 gph, 55 psi)
https://www.northerntool.com/shop/tools/product_200672183_20... (580 gph, 50 psi)


Any suggestions or input? I'm looking to keep the cost of the pump at around $100. I'm guessing 100 gph at 50psi are my target outputs, but I'm not exactly sure what that corresponds to at the typical max flow rate @ 0 psi and min flow rate @ max psi ratings that datasheets give? I have considered buying a cheap Harbor Freight vacuum pump but I don't need that much vacuum and using a needle valve to reduce vacuum will (apparently) cause the pump to puke oil all over. It seems like building a recirculating aspirator is the best route, if I can just find a reasonable pump.

[Edited on 6-3-2018 by monolithic]

Vosoryx - 5-3-2018 at 20:03

This might help:

http://www.sciencemadness.org/talk/viewthread.php?tid=78427

It works fine for most everything i've thrown at it thus far.
100 psi 5 lpm for the water pump.

monolithic - 5-3-2018 at 20:31

Quote: Originally posted by Vosoryx  
This might help:

http://www.sciencemadness.org/talk/viewthread.php?tid=78427

It works fine for most everything i've thrown at it thus far.
100 psi 5 lpm for the water pump.


Do you happen to know much vacuum it can pull?

Vosoryx - 5-3-2018 at 20:46

Actually, not off the top of my head.

I tested it by boiling water with a thermometer in it, but that number is currently written in the back of my lab journal. Usually not a problem, but i'm away from home right now. Sorry.
Other amateurs have had a lot of success with aspirators though. I seem to remember nurdrage used the same specs on the water pump... I think he got water to boil ~20 C.

monolithic - 6-3-2018 at 19:49

Quote: Originally posted by Vosoryx  
Actually, not off the top of my head.

I tested it by boiling water with a thermometer in it, but that number is currently written in the back of my lab journal. Usually not a problem, but i'm away from home right now. Sorry.
Other amateurs have had a lot of success with aspirators though. I seem to remember nurdrage used the same specs on the water pump... I think he got water to boil ~20 C.


Yes, I saw the one he built in his video performed amazingly. The replies to his videos said his results weren't typical. Even in your thread, the other poster was complaining that his vacuum was weak. If you have the time, I'm curious to see what the boiling point of water under vacuum was for your setup. :)

Vosoryx - 6-3-2018 at 20:33

Yeah, i'll let you know once I get back to my lab next week-ish.

FireLion3 - 6-3-2018 at 21:55

Quote: Originally posted by monolithic  

A used Procon pump, but 125gph and 175psi is way overkill and might blow up the aspirator.



125gph, did you mean gpm? I tried to use a 3gpm / 180 gph diaphragm pump to recirculate water for my aspirator and it was completely ineffective, whereas the aspirator worked fine on the faucet. I tried this using a different pump as well with a slightly higher flow rate. With both pumps, the vacuum that gets pulled is so insignificant that it's basically useless.

At the time I speculated that the lack of vacuum was caused by the pulsing rhythm of the pumps, as it was the only clear difference I could notice between a faucet stream and the stream from the pump.


If you only need around vacuum aspirator level vacuum, you could look into buying a used diaphragm pump on eBay. They're often very cheap and durable, and do not require changing oil (which would often become contaminated with solvents from vacuum filtration)

monolithic - 7-3-2018 at 01:32

Quote: Originally posted by FireLion3  
Quote: Originally posted by monolithic  

A used Procon pump, but 125gph and 175psi is way overkill and might blow up the aspirator.



125gph, did you mean gpm? I tried to use a 3gpm / 180 gph diaphragm pump to recirculate water for my aspirator and it was completely ineffective, whereas the aspirator worked fine on the faucet. I tried this using a different pump as well with a slightly higher flow rate. With both pumps, the vacuum that gets pulled is so insignificant that it's basically useless.

At the time I speculated that the lack of vacuum was caused by the pulsing rhythm of the pumps, as it was the only clear difference I could notice between a faucet stream and the stream from the pump.


If you only need around vacuum aspirator level vacuum, you could look into buying a used diaphragm pump on eBay. They're often very cheap and durable, and do not require changing oil (which would often become contaminated with solvents from vacuum filtration)


No, 125gph. If it was 125gpm it would be super overkill. :) When you say you recommend buying a used diaphragm pump, you're referring to a vacuum pump?

Sulaiman - 7-3-2018 at 04:27

If just for vacuum filtration I can recommend this https://www.ebay.co.uk/itm/DC-12V-24V-80Kpa-Micro-Piston-Vac...
you would also need 12 Vdc at up to 2 Adc - a dedicated power supply, PC PSU, car battery etc.
Water boils at 65oC or less with this pump and I ran it for days continuously with no problems.