# Adjusting OPV. Water leaking from Portafilter when under pressure.



## _shakeyjake_ (Dec 16, 2016)

I've had a bit of an odd outcome every time I try to check the OPV setting on my ISOMAC Millennium.

I have a pressure gauge that I fit to the portafilter. When locked into the grouphead, water somehow flows past the grouphead seal so I can't get an accurate pressure reading.

When I do normal backflush routines, this never happens. Always seals.

What am I doing incorrectly? Why would this happen?


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## ashcroc (Oct 28, 2016)

_shakeyjake_ said:


> I've had a bit of an odd outcome every time I try to check the OPV setting on my ISOMAC Millennium.
> 
> I have a pressure gauge that I fit to the portafilter. When locked into the grouphead, water somehow flows past the grouphead seal so I can't get an accurate pressure reading.
> 
> ...


No basket when checking OPV means the portafilter turns more before locking off. If the group gasket is old & hard it'll be formed to the shape of the basket too.


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## _shakeyjake_ (Dec 16, 2016)

ashcroc said:


> No basket when checking OPV means the portafilter turns more before locking off. If the group gasket is old & hard it'll be formed to the shape of the basket too.


Hi! Thanks for the quick reply.

To expand upon what I do and don't do.

-Always have kept the basket in, so it seals properly. Should I be doing this? I only assumed I should because it Should seal better (clearly not at the moment!)

-Group gasket is very new. I overhauled the machine only a month or two ago. This was replaced, so should be OK.

I do also pre fill the portafilter/gauge with water. Should this be done?

I assumed I should to get a more accurate reading because of the lack of air. I could be wrong in thinking this?

Thoughts?


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## DavecUK (Aug 6, 2013)

*When using a pressure measuring portafilter, never use a basket, because it can't seal.* Also always ensure the portafilter has an unbroken rim, some have 3 small vertical slots cut into the rim (god knows why).

P.S. When not using a basket, don't lock it in too hard the sharper rim can damage the group gasket.


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## _shakeyjake_ (Dec 16, 2016)

OK, no basket. Will try that.

Should I fill the portafilter with water first or just attach it dry and test?


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## ashcroc (Oct 28, 2016)

_shakeyjake_ said:


> OK, no basket. Will try that.
> 
> Should I fill the portafilter with water first or just attach it dry and test?


Fill with water first. The needle will jump around otherwise until the OPV has let the air out.


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## _shakeyjake_ (Dec 16, 2016)

ashcroc said:


> Fill with water first. The needle will jump around otherwise until the OPV has let the air out.


Cool. Will give it a go again!

Thanks all.


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## _shakeyjake_ (Dec 16, 2016)

Can conform, you guys know what your talking about. Tried without basket. Didn't leak. Perfect!


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## _shakeyjake_ (Dec 16, 2016)

Can conform, you guys know what your talking about. Tried without basket. Didn't leak. Perfect!


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## DavecUK (Aug 6, 2013)

_shakeyjake_ said:


> Can conform, you guys know what your talking about. Tried without basket. Didn't leak. Perfect!


Glad it's solved, it's the sort of embedded knowledge of experience that often we take for granted and assume everyone knowws....which of course is not the case. Just remember the water expansion on heating when setting pressure, otherwise you will get the wrong result.


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## _shakeyjake_ (Dec 16, 2016)

DavecUK said:


> Glad it's solved, it's the sort of embedded knowledge of experience that often we take for granted and assume everyone knowws....which of course is not the case. Just remember the water expansion on heating when setting pressure, otherwise you will get the wrong result.


I know what you mean. Seems like a straightforward process but there's a knack to it all.

Noted on the water temp. I was watching your video yesterday about setting the Expansion Valve on the Minima and you did it when cold (or set the boiler to not heat).

If its tested and set to 9bar when cold, would it not actually sit higher when warm, because of expansion?

Would it not make more sense to set it when warmed up to fully functional temperature? So that you get the 9bar exactly.


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## DavecUK (Aug 6, 2013)

_shakeyjake_ said:


> I know what you mean. Seems like a straightforward process but there's a knack to it all.
> 
> Noted on the water temp. I was watching your video yesterday about setting the Expansion Valve on the Minima and you did it when cold (or set the boiler to not heat).
> 
> ...


No trust me on this, that's not how it works.


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