Finally finished addjusting my water jet pumt (water vacuum pump), it's made totally from things one can by at hardware store. And it's comparable in performance with commercial pump of same type :)

Heres a shematic pic of it:
http://www.geocities.com/frogfot/stuff/waterjetvac.png (copy&past)

This thing consists of 1 brass T joint, 3 pipe adapters and brass pipe inside (dimentions specified in pic). Brass pipe was sharpened with a file. Rubber pipe on outlet is about 15 cm long. The small PVC pipe inside (red) is cable isolation, it got 4 mm inside diam. and it was formed to disired shape with help of heat and glued in place by epoxy.

Some about it's performance
I borrowed a "vacuum-meter" from dads lab and compared my pump with real jet pump. Real pump gave 9 torr @ 9*C water. My homemade pump gave down to 13 torr @ 9*C :D

I've also compared capacity. Real pump sucked 300 ml water per 3-4,5 s, while my did same volume per 7,5 s. Thats twice as slow, but! real pump consumed 1,5 kg tap water per 10 s while my did only 0,8 kg per 10 s! Seems like consumption of water is proportionall to pumps capacity.

IMO pumps capacity can be easily increased together with consumption of water by addjusting length of brass pipe (the one inside). Also, making this pipe sharper would probably play a role too. This way one could easily addjust pipe to ones needs.

Anybody played with this? Also, have anybody thoat of a simple way (cheap) to measure vacuum? Cause commercial manometer can be pretty expencive.
I've thoat about a syrigne connected to weighting scale (the one we usually weight fish with), but never tested this.. have limited time. Wanna add this on my page in nearest future.

I'll post a photo of pump when there will be some free time..

EDIT: Forgot to mention that in the beginning I injected water into upper inlet, this gave only down to 250 torr. Idea to inject water into side inlet came from a picture here:
http://www.kinetic-therm.com/english/product/ejec-thermo-vac/ejec-thermo-vac.htm

Wonderful - a ghetto aspirator for $10. Definitely beats the kimble-kontes prices of ~$70. A 13 torr vacuum is adequate for nitric acid concentration. You can rip a vacuum gauge off an old no-longer-functional bike pump or a cheap hand pump, if you desperately need to measure the vacuum.

to use a standard pressure guage as a vacuum guage, wouldn't you have to put the body of the guage inside the vacuum and port the fitting to the outside world?

When I had to test my recirculating vacuum setup, I heated various pure liquids with known boiling points and then applied suction. The liquids started boiling when the pressure dropped, and continued to do so until the temperature dependent vapour pressure was equal to the reduced pressure from the pump. Having monitored the temp all the way through, it was easy to calculate the pressure in the vessel. I did it with both water and ethanol and they gave exactly the same value, so I'd say that the method is reliable.
Of course, this is only useful for determining the capacity of a pump, not for routinely monitoring the vacuum in your destillations.

Microtek's method is probably the most convenient, but you might also want to try measuring the vacuum with a simply made U-tube manometer, like shown here (http://www.rverscorner.com/articles/manometer.html). After calibrating it would directly show the pressure loss quite accurately, and would also allow a constant monitoring of pressure during distillations..

Nice idea Microtek, thats probably the cheapest way. Have tested this while checking real pressure by digital manometer, this gave surprising results. Temp got to 14*C ==> 12 torr, while real pressure was 11 torr. Gonna use destilled water next time (just to see if there are any difference).
In some cases one could probably use this method continiuosly, but water would dry out..

In U manometer one should change out water with other liquid with high boiling point (paraffine?) since water can dry out here too..

Some more on vacuum technique :
The Bell Jar (http://www.belljar.net/articles.htm) Check the first five articles
Sam's Laser FAQ (http://www.repairfaq.org/sam/lasercva.htm#cvatoc) The vacuum section.

I like Microteks idea, an excellant way to calibrate a homebuilt gauge.

hmm the picture does not want to load at this moment...

Made finall version of pump and wrote a text on it:
http://www.geocities.com/frogfot/misc/waterjetvac.html
There more pics, they all should show..
Pump showed to be better than ever, I got a table in bottom of page that compares commercial and homemade pumps.

Tautara, I finally read all theese sources and they seem to be about pumps that go down below 1 torr.. Heh, now I wanna make an electrical pump :)

Btw, I realised that there was already thread on respirators, though, before, I didn't knew they were called respirators :P

This may be stupid, but can someone tell me what is the advantage of using aspirator over using compressure of a refrigerator that I got(second hand) for 300Rs.(7$)?
I mean is there any diffrence in performence? I couldn't measure the pressure but it seems to work well. Or aspirator is able to generate better vaccume? If someone have used both then he/she;) can help.

The only advantages to an aspirator, in my opinion, are first, it pulls a greater volume of gas per minute than an average refrigerator pump, and second, it dilutes and discharges any noxious vapors. For example, if you're distilling nitric acid, the vapors will eat your pump in pretty short order. Also, even water vapor will contaminate the oil in a fridge pump to where it'll not work well. One other minor hazard with a fridge pump is the compression stroke in the cylinder. If you have a flammable mixture of say, xylene and air from a solvent evaporation, the compression in the pump can work like a deisel engine and explode, ruining the pump and possibly your whole day.

I have an aspirator, a manual vacuum pump(diagnostic type used on cars),
and an electric continuous vane pump. It depends on the application.

The best one I've used for nitric acid is the aspirator. Gives sufficient
vacuum, is quiet, gets rid of noxious gases, and is cheap(cost only $9).

With the electric, a water bottle is necessary to prevent corrosion of the
pump and the beast makes too much noise in my apartment building,
drawing both unwanted and unnecessary attention to my hobby. So I'll
relegate this one to my automotive air conditioning sideline(profitable).

With the manual, it's not practical because of the continuous pumping
that would be required. I use it for filtrations of hydrazine and high
mesh aluminum powder(in alcohol).

The max vacuum of a water aspirator equals the vapor pressure of your water. So, if you'd make an NaCl/ice bath and pump the water through the aspirator using an ordinary water pump, you could achieve quite some spectacular results.

The max vacuum of a water aspirator equals the vapor pressure of your water. So, if you'd make an NaCl/ice bath and pump the water through the aspirator using an ordinary water pump, you could achieve quite some spectacular results.

Thats a myth.
The vacuum which is to reach by an aspirator is actually lower than the theoretical determined by the water temperature. Yes I HAVE references for this.

Just think: If the vacuum reaches the point where water goes gaseous, what will happen? The water evaporating will of course strongly cool the jet. hehe....

In realworld the vacuum which can be reached by any vacuum source is mainly determined by other things, like tubing length and diameter etc. pipapo. Using HARD tubing of rather big diameter (20mm for an aspirator is ok) helps more than waterpressure or watercooling or whatever as vacuum which never reaches your flask is no vacuum at all. Thats it.
:p

Nice I was looking for something like this sounds good. I am going to giv eit a go.

(We'll expect results shortly - kingspaz)

If any of the things you guys posted works for me...you are mine heroes...well not exactly me I have a friend who got a job in the place I call Never-Go-Land and the working conditions are atrocious (I didn't belive but, yes, I did go there once - and it is disaster). I will try to make him a water pump as described here since he does have one and he need it. Since he have very low water pressure I guess we will have to use the water tank-electric pump recirculating system.

Any UK members intending to build an aspirator type pump as described in this thread may want to check out this (http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=57230&item=4321623051&rd=1) eBay item and hit "buy it now".

It will cost you �65 inc. P&P and for 1.5 horse power that is an absolute bargain from what I have seen. A pump like that would cost around �180 new, 0.5 hp would cost around �140. The reason I don't snap it up myself is that I need only my vacuum cleaner suction for filtrations, and I believe my water pressure is high enough for a suitable aspirator should I wish to do vacuum distillations. I have other projects the money is better spent on, but I thought someone here might have it high on their list of priorities and would like to know.

if some have watertank-electric pump-aspirator setup and likes to mess a bit:
replace water with diesel fuel or low-viscosity oil.should be better vacuum.

With frogfots good directions I constructed a water aspirator but due to incorrect usage of glue the brass tube kept moving out of correct position and needed constant adjustment.

I ordered, at a price of 20$, a stainless steel aspirator from Cynmar but it did not work! I called them and they were very friendly and I have now returned the one I have for one that works. They tend to be helpfull when you use chemical and lab terms fluently.

Once I get it I can make formalin and thus make PE and Hexamine! : )