Welch duoseal 1400 vs Edwards.

Hey guys. It’s time for me to start dabbling in distillation finally. The people I work with have most of the glassware I need, minus the cold trap and the vacuum pump of course.The last people that I worked with had a turn key set up from open source steel that included the Welch during seal 1400 pump. I see the pump is fairly standard on Turnkey set ups or entry-level distillation I guess. When I mentioned it to a buddy of mine he mentioned I should go with an Edwards. I see there’s a pretty big price gap, so I’m basically just wondering what you guys would suggest for my first deep vacuum pump for distillation. We have the capital and Intentions to upscale the distillation for sure, so I’m trying to find the balance between a good pump to start with, and avoiding the whole damn for $1000 more I could’ve got something 10 times better situation. Thanks fo any advice

I use the Edwards EM-28 and bought it used from craigslist without warranty for $1000 delivered. This is the same thing mostly as most Edwards pumps. They are direct drive and as such the noise level does not preclude conversation with the pump running nearby. In fact most of my vids are shot with the pump running. one reason the pump is quiet is the direct drive mechanism can be buried down into the core of the pump which is surrounded by oil and metal and such. The price used and rebuilt with warranty is about $2500. The listed maintenance intervals are measured in thousands of hours and the pump is designed and safe for continuous duty use 24/7.

The Welch pumps are belt driven as a rule. Belts are exposed but not in an unsafe way. Still though the exposure lends itself to transmitting more noise and any exposed surface in a contaminated environment of a factory will require more maintenance but not nearly so much more as to be a major concern during purchase decisions. The advantage gained by a belt driven arrangement are it is less expensive to manufacture and therefor less costly to the end user as a rule. Further the belt arrangement decouples the primary source of heat, the motor, from the vacuum oil. Generally the hotter the oil becomes the less tolerant of contamination the pump is in the oil and vacuum can suffer. The price of a new Welch 1400 model when I was shopping was only about $600 more than my 3 year old used Edwards without warranty. So far heat build up has not been an issue for me with a direct drive motor.

I would definately place the two pumps into different classes of performance over the long haul as should be obvious from the prices generally asked. Both companies know full well how to make fine gear for the price. This is a one time expenditure for an operation as a rule but also consider my own story. I bought my pump after somebody else had used it daily for three years and jumped at the chance of buying it for $1000. I would never of course pay that much for a belt driven unit used in similar fashion which frankly given the obvious zero maintenance policy of the last owner might not even work by that time lol. So the point is that you pay more but also can liquidate for more and have more value stored this way when the time to upgrade/renew does present itself and you need to sell it.



I own both pumps (e2m28). I have an open source 5 liter and use it every day for production.

Welch (bought new from open source): A bit slow to pull a vac (frustrating when switching balls/cows mid run). My biggest problem with the Welch is how often you need to change it’s super expensive oil. You can only do 2 or 3 first pass before you need to flush and refill the oil. Besides that it works fine on my 5 liter. (Pulls to .25 micron)

E2M28: I bought this one used from Ebay for like $1200. I bought the rebuild kit from Edwards for about $600. Rebuilt it and cleaned it, and it pulls to .6 micron (lower than spec!). This thing is an absolute BEAST. It’s not even fair to compare performance on these two pumps. The edwards could probably do a batch with water in the oil tank. It’s a damn tank.

I guess it depends what size system you’re getting, and how often you’re planning on using it. 2 liter, I’d go Welch (edwards would be big time overkill). If you’re getting a 5 liter and plan on banging runs through it all day, look into an edwards. I would highly recommend looking for used ones and either paying to rebuild or doing yourself.

Hope this helps, and I’m happy to answer any more questions or elaborate.



How easy was it to do a rebuild, the price difference for the kit and to pay someone isn’t very much but I like to know who’s to do it in case I can’t have down time

I’m only semi-retarded and it took me 4 hours. :grin: It was not easy at all, but it’s my idea of fun so I went for it.


How tough a rebuild wthout a shop but in a lab room? Tips on rebuilding?

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We didn’t do it in a shop. We did it in our lab. You’ll some tools though. Pliers, wrenches allen keys, screwdrivers. The basics.

We went off this:

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Do you guys know how to interpret the model nos? Edwards e2m0.7 vs e2m5 etc. Is e2 a series or generation and the m# the cfm?

Summit sells the Edwards 30w/2L systems, and now they sell a dual Edwards 30 setup with the 5L I believe.

Answered my own question, should have just done more research. My guess was fairly accurate the mX number is the size/volume. M28 replaces the discontinued m30. m30 could probably be had used cheaper on eBay since it’s the older discontinued 21cfm model. This big boy is 1.5hp 240v pumps down to .7 micron if I’m not mistaken

Almost positive the Edwards 30 also gets down to 3/4 micron according to @Beaker videos.

My M28 does get down to .75 micron (¾ micron) routinely as reported by the Pirani based sensor.


Has anyone tried using other pump oil in their welch?

It also looks like the rebuild kits are interchangeable? I saw the great prices of the M30 on ebay yesterday, but I was a bit concerned I wouldn’t be able to find a rebuild kit for a discontinued model. From what I’m seeing now from other vendors of the kits though, it looks like a M28 kit will work fine in an M30… Am I wrong in assuming this?

This is one of the most helpful replies I’ve seen about this topic…

We currently are running a 5L short path set up and we were trying to use one of those cheap amazon 3.5cfm rotary pumps… lol

Obviously didn’t work too well, we’re barely able to get down below 1100 microns.

That being said, we have a Welch duo seal 1400 belt driven pump and we were considering doing a small overhaul on it today, but we didn’t want to waste the time if it wouldn’t pull down low enough on our system. So if I’m reading this correctly, you were able to get yours down to .25 micron on a 5L short path?? If that’s the case we will gladly get that thing like new again.

Hey. We had to put our Edwards on our two 7.5cu vac ovens because they pull them down much faster than any other pump we have. So currently we use the DuoSeal for our 5liter setup.

We do two passes on distillate. First pass the vacuum level rarely goes below 1000 micron. The second pass we generally get 250-350micron. We are able to achieve 85-95% THC and beautiful color (material dependent).
We usually start pulling THC under 200c (on 2nd pass).

I have not tested the depth of the pump without being hooked up to the system, but I believe it is rated to go close to or under 1 micron.

We change the oil every 1-2 runs. Best to change after 1st pass.

Hope this helps.

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That welch 1400 will do fine. Best to blank it off amd get a micron reading. Under 20 microns and your good. Then plumb to your spd, and pull it again. Hoping to be under 150 micron for the run

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Yes food grade mineral oil works fine

Sorry, but I’m not putting food grade mineral oil in my 3000.00 vac pump.

Grade 19 or 20 only in my vac pumps.

I’ll leave the mineral oil to @TrueTerpenes scams.


Wait… are u saying food grade mineral oil as your pump oil?

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