Common Espresso Machine O-rings & Copper Sealing Washers

AS-568 is the Aerospace Standard (AS) as well as the SAE (Society of Automotive Engineers) standard and is used for military and industrial manufacturing in North America.

See this website for a sizing chart on AS 568 O-rings: http://www.oringsusa.com/html/o-rings.html

See this website for a sizing chart on Italian specification O-rings: http://mdmetric.com/or/corda1gb.htm

LM Linea Check Valve(s)

AS-568 size: -012
McMaster-Carr P/N 9561K13
Material = NSF Certified EPDM

Vacuum Breaker Valve O-ring

OR 102 (Italian designation)
AS-568 size: -007
McMaster-Carr P/N 9396K12
Material = Silicone

Brew Solenoid Valve O-rings

OR 105 (Italian designation)
AS-568 size: -010
McMaster-Carr P/N P/N 9396K15
Material = Silicone

Ulka Pump Priming Valve

OR 2025 (Italian designation)
AS-568 size: -010
McMaster-Carr P/N P/N 9396K15
Material = Silicone

"Hardware store" o-rings will work fine for the priming valve but will not meet the temperature requirements of the others. See this website pdf for a nice sizing chart on sealing washers: http://mdmetric.com/tech/DIN7603tdc.pdf

If anyone has another "common" o-ring, I will gladly do my best to add to the original list. As always, negative comments greatly appreciated.

Eric, thanks for posting this list and thank you for the off-line help. I found out that the vacuum breaker valve on my Brasilia is not closing all the way even with enough pressure. If I am going to take it out to do a descale, I might as well replace it with the new one from Chris. The one currently on this machine uses a copper washer as a seal. What size is this washer, assuming this valve is of typical size for E61 type home espresso machines? Could I use this washer type with the new valve or is it secured differently? Thanks.

The shape/size of the hex on the bottom of your existing vacuum breaker valve is designed for a copper sealing washer whereas typical vacuum breaker valves (including the new style sold by Chris' Coffee) are not. Apply about 2-3 match heads worth of Loctite 567 to the threads of the new valve and it will seal well.

The thread size of most vacuum breaker valves is 1/4" BSPP (a little over 0.50" OD).

Eric, this is great. I'm looking forward to getting some silicone spares for the vacuum breaker valve on my machine. I wish I'd seen this before yesterday; my GS3's steam wand valve seat had been acting up a bit lately (taking a long time to close all the way after steaming), and I pulled it last night to re-lube the o-rings/gaskets. There are 3 relevant ones; at least 2 of them are definitely o-rings and I think the 3rd as well, though that's only if its face was totally flattened by the mating surface (which I assume is very much the case). It would have been nice to get the calipers out and check that.

Thanks.

I've added the Maryland Metrics site page for Italian specification o-rings to the original post. As you can imagine, some espresso machine manufacturers are fairly explicit in describing their o-ring applications and others are less so.

I had to flush the round sight glass on my Linea (some fluffy stuff floating around in there) and the little drain plug under it will not seal. Is there something better then a new copper washer for this spot?
Thank, Duke Masters

MAYBE.

Firstly, new copper washers for a 6 mm threaded screw SHOULD be available from your local "friendly" German car parts store. They show the size as 6 x 12 whereas the ones I use all the time are 6 x 10 (all nominal). You could substitute a teflon washer if you can find one at the local store.