# Isomac Tea - curing that spritzing



## centaursailing (Feb 27, 2012)

I've tried everything I could think of except, on the advice of Peter at My Espresso Ltd not to do it, adjusting the pressure at the group head. Nothing worked and the spritzing remained to plague me and prevent me from using weight instead of volume for extraction ratios I've read about here (1:1.6). Finally, after a fair bit of research, I got up the courage to locate and adjust the Over Pressure Valve. What was giving me trouble was that the adjustment collar was screwed right in and I couldn't find anything to adjust and had to work it out by tracing tubes and pipes. No wonder I was getting the spritzers, the pressure was about as high as it could be due to no release from the OPV. Using a blind filter I got a consistent 9.5 bar on the group head pressure gauge and about 8.5 to 9 through coffee in a filter basket.









Having had such trouble in identifying the OPV, while the housings were off I took a photo of the important bits and added some notes which I hope may help other owners of the Isomac Tea with a similar story.

Rod


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## funinacup (Aug 30, 2010)

Good detective work! Are you shots better as a result?


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## 4085 (Nov 23, 2012)

Rod, has this cured your problem then? Spritzing, even though your bar pressure seemed high, is obviously the water finding the easiest route through the puck, so if your distribution or tamp is wrong, should in theory still occur.


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## centaursailing (Feb 27, 2012)

Thanks funinacup, the shots are better, they've got a fuller rounder taste.

David, yes it does seem to cured the problem. After my visit to your place, I've been using the end of a straightened paper clip in a stirring motion before tamping. I will be honest though, I tried the nutation technique you showed me but then forgot to use it every time - might explain the occasional pin hole and tiny spritzer but overall the improvement is massive! Thanks again.

Rod


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## DavecUK (Aug 6, 2013)

Incredible in 7 years Isomac have changed nothing about their machine by the look of the parts I can see and comparing with my photo archive.....can't remember who bought them,, might have been Crem?


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## marcuswar (Aug 19, 2013)

I've meaning to adjust the OPV on my TEA for ages. I've tried a few times but mine seems to be stuck solid. The built in pressure gauge shows 11bar when pulling a shot so it could definitely do with reducing. How exactly did you turn the opv? did you grip the tube with pliers and turn ? I tried this but it just started to tear the tubing ?


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## centaursailing (Feb 27, 2012)

Hi Marcus

Pliers on the brass collar rather than the tubing. I was as gentle on squeezing the pliers as possible while still getting the collar to turn, which it did fairly easily once I had a good grip, however I did leave some scratch marks on the collar from the pliers. If you can't see any of the collar protruding you could try removing the tubing, when the machine is cool, which is likely to result in a flow of water, a tapered plastic or similar spigot could be pushed into fitting to stem the flow while the brass connection onto which the tubing fits could be turned until the collar becomes accessible.

Claudette at Bella Barista told me "The OPV valve used (in my photo) looks the same as the one Expobar used to use. There are better OPV's available now..." so that may be another option for you. If you decide to go this route, I'd be grateful to you post the details here of the replacement you used and how it looks for everyone to see.

Rod


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## DavecUK (Aug 6, 2013)

centaursailing said:


> Claudette at Bella Barista told me "The OPV valve used (in my photo) looks the same as the one Expobar used to use. There are better OPV's available now..." so that may be another option for you. If you decide to go this route, I'd be grateful to you post the details here of the replacement you used and how it looks for everyone to see.Rod


it's not the same expansion valve as the Expobars..in the expobars you used a flathead screwdriver to adjust them via a screw in valve on one end. The expansion valve you could use is the same as on the Duetto and many other machines, but you will find it a little awkward to fit and will have to buy some fittings as well I think.

http://coffeetime.wikidot.com/opv-over-pressure-valve

Have a read, the middle valve is the one Expobar used/still use and the one on the right is used in the Duetto, alex, vivi, QM etc..


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## centaursailing (Feb 27, 2012)

Thanks for the clarification and link Dave. Just in case the URL changes I've downloaded your pdf to keep for reference.

Rod


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## marcuswar (Aug 19, 2013)

Hi Rod.

Thanks for the info. I'm sure I tried it like that last time I tried but the pliers just slipped around and started to scratch it, that's why I think I tried gripping the tubing instead. I'll give it another go later when the machines cooled down.

Its a really annoyingly designed OPV, the Classic's was much easier. Would it have killed them to put two flat edges on the collar so we could use a spanner or even make the exit hole hexagonal so we could use an Allen key in it!

Pulling the tube off is no worries I've removed it a number of times and have recently replaced it with a new longer tube when I insulated the boiler and had to reroute it. Now we have an actual ISOMAC sub forum I'll post some pictures later.


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## marcuswar (Aug 19, 2013)

Well I had "the lid" off my Isomac this morning and tried to adjust the OPV but its a solid as rock, won't budge at all. I'm seriously tempted to file two flat spots on it so I can more leverage with a spanner rather than trying to use a pair of pliers.

My pump pressure gauge has started to fluctuate madly all the time now (it used to do it just occasionally) so either I've got air in it somehow or the OPV is misbehaving.


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## centaursailing (Feb 27, 2012)

Might be worth having a replacement OPV on hand, if they aren't expensive, just in case the old one 'gets damaged beyond use' or can't be fixed then you have the necessary ready and waiting?


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## marcuswar (Aug 19, 2013)

Yeah I was thinking the same. The OPV are £15 from Ferrari espresso but the problem is where do you draw the line. I could have a complete machine in spare parts just in case! At the end of the day this is why I kept my old Gaggia classic as a backup machine.


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## centaursailing (Feb 27, 2012)

Snap! I used to carry so many spares on board our yacht that we often joked it would be easier to tow a spare yacht to be cannibalised for spares


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## marcuswar (Aug 19, 2013)

Inspired by a comment made by another member regarding his wife suggesting using a heat gun to free up his OPV I had a go at mine again and it worked. A quick 20second blast with the heat gun and the OPV valve could be adjusted









I used one of the nozzle attachments for the heatgun as a heat shield and heated the body of the OPV (i.e. expand the casing).










After heating I turned the valve about 1 or 2mm anticlockwise to adjust the pressure down by 1bar. Those scratch marks (from a previous attempt) were originally at the 12 O'clock position.










Checked the pressure both with the built in pressure guide my home made pressure gauge in the naked portafilter. The static pressure showed as about 10bar on both and when pulling a shot this seemed to equate to about 9-9.5bar (needle on the built in gauge was fluctuating do hard to be exact).


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## El carajillo (Mar 16, 2013)

Marcus , it be worth totally unscrewing the valve centre cleaning and greasing with Molycote 111 to include the seal(s) as well


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## marcuswar (Aug 19, 2013)

Thanks for the comment ElCarajillo , I have some Molycote so may strip it down completely next time I have a couple of hours spare. Since it was stuck solid initially I can only assume it was scaled up so could probably do with a proper clean anyway. I assume I just keep unscrewing the nipple end and it will come out with the spring and seal?


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