View Full Version : Do you use a dedicated Pressure/Vacuum manifold?

19-01-2017, 10:44 AM
Hello everyone,

A simple one really, I wondered how many of you have a dedicated pressure and vacuum testing manifold and your thoughts on how necessary they are?

I ask because a lot of literature Iíve been reading suggests that normal charging hoses arenít rated for vacuum and may leak slightly under vacuum. Even product catalogues, in the blurb about the PVR manifolds, point this out. Also to consider is the fact that the gauges on charging manifolds arenít accurate enough to show ďsmallerĒ leaks of either vacuum or OFN when vacuum/pressure testing (though I know correct practice is to use a dedicated vacuum gauge anyway, perhaps negating the need for a manifold gauge as well).

However, I was told that they arenít necessary. And all Youtube vids that Iíve been looking at to educate myself on the vacuum and OFN testing stages use OFN and the vacuum pump in through the service hose of the normal charging manifold that was used for recovery. Nobody in reality (well, that Iíve seen in my limited experience) uses a charging manifold to recover, swaps over the manifolds to draw vacuum with a dedicated PVR manifold, then swaps back to the charging manifold to charge the system.

I see that most manufacturers of equipment provide 4-way charging manifolds such that a vacuum pump may be attached without swapping the service hose from recovery machine to vacuum pump as you do on 2 way manifolds. I would reason that if manufacturers of charging manifolds provide equipment such as 4-way charging manifolds, then itís perfectly acceptable to use regular charging manifolds for the vacuum stage - otherwise there would be no market for them.

One may also use a vacuum rated hose from the manifold to the vacuum pump, but I would reason that this is redundant if the rest of the hoses are regular hoses and the manifold is a regular manifold. A chain is only as strong as it's weakest link and all that.

Iíve been debating all this with myself as I want to do things correctly but then itís a waste of money if the reality is no one really uses them because in actual fact they just arenít necessary. But I've been going around in circles with it and could do with some help. Does the wider collective have some opinions on this?

Do you use them? Are they a necessity? Or are they unnecessary?

Thanks for your time


Rob White
19-01-2017, 12:39 PM

I do use separate vac gauges and I always
fit them as far away from the vac pump as possible.

This is not possible on some systems and most AC kit,
so the manifolds with a port on for a gauge is the only

I do know you should use the largest diameter pipe you
can get 3/8 at least because the normal gauge lines are
too narrow.



21-01-2017, 12:03 PM
Start using good micron vacuum gage (like BlueVac) and you will immediately know answers to your above dilemmas!

23-01-2017, 02:44 PM
I was referring to the use of the manifold pressure/vacuum gauges such as the Javac PVR pressure testing manifold rather than the digital vacuum gauge.

I thought it was the case that standard charging manifolds and hoses aren't vacuum rated

23-01-2017, 04:27 PM
I use JB-DV-22N electronic vacuum gauge,

Because it has 1/1000 accuracy, it can tell if there is the smallest leak.

23-01-2017, 04:50 PM
I was referring to the use of the manifold pressure/vacuum gauges such as the Javac PVR pressure testing manifold rather than the digital vacuum gauge.

I thought it was the case that standard charging manifolds and hoses aren't vacuum rated

You are right! They aren't! But you cannot see that with your own eyes without using micron gage. And it is important that on the jobsite you work without presumption that something is vacuum tight. You should be able to measure it. That cannot be done without micron meter!


In practice, it is not absolutely necessary that manifolds and hoses are vacuum tight, until you start to make vacuum holding and rise rate test. While pump is pumping, you can still make your required target vacuum level and hold it at that level, with hoses and manifolds even if they are not 20 microns rated. But you need to isolate them from system and micron gage with vacuum tight isolation valve.
This is one of them:


Good new O rings and Nylog is your friend!

23-01-2017, 10:34 PM
Personally I don't use a separate manifold for charging but I do have a vacuum/recovery set up that I use.

My hoses are 1/2" one end and 1/4" the other end. I have two of these hoses that connect directly onto a tie piece from my vacuum pump.
This coupled with vacuum rated core removal tools, both 1/4 and 5/16" and my Accutools Bluvac.

The amount of time it saves when trying to vac a large system really is extraordinary.

While at first it may seem counter intuitive to use large diameter hoses the value rapidly becomes apparent after starting the evacuation. 1/2" hoses will decrease the time required for evacuation by a factor of 16 times over the typical 1/4" hoses used by most of the industry. Larger hoses reduce friction and therefore increase conductance speed. The conductance speed of 1/4" hose is so small it should never be used for evacuation.