HB wrote:Have you tried soaking the vacuum breaker in descaler (or even vinegar)? It may have some residual dirt / scale buildup that is making it stick or fail to seal. The one on the left has the reputation of sticking easily. The one on the right is a vacuum breaker with a heavier pin and Teflon sleeve, so it resists sticking.

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I don't know which one La Marzocco uses, but I've used a good number of consumer espresso machines and they rarely have trouble with the vacuum breaker sticking or failing to seal.

The GS/3 used the vacuum breaker on the right.

HB wrote:I don't know which one La Marzocco uses, but I've used a good number of consumer espresso machines and they rarely have trouble with the vacuum breaker sticking or failing to seal.

This is usually more or less a function of the TDS of your water, I think (regardless of whether your water is softened). People with high-TDS water will generally have more trouble with their vacuum breakers even if they soften their water-unless they use RO. That's just because, as said earlier, the water that accumulates above the actual steam boiler chamber itself, including right on the Teflon and valve o-ring, evaporates fully from the heat of the boiler, leaving behind all solids it has in it. This builds up over time on the o-ring and starts a slow leak. It's why I leave my GS3 on 24/7 when I am home, because it starts to leak and hiss slightly every couple of months with my ~250ppm TDS water if I turn it off every night.

There's no need to ever replace a whole vacuum breaker valve of the kind on the right in Dan's photo (which LM uses). You can very easily take it apart and scrub any buildup off of the teflon (comes off very easily with a brush) and the o-ring. I personally recommend pulling off the o-ring from the pin it's mounted on and applying lubrication on it (dow corning 111); this will make it seal a little better and also extend how long it lasts before cracking into pieces, in my experience.

another_jim wrote:In a pressure controlled steam boiler, a stuck vacuum breaker means false pressure at start up and a cold boiler. In a temperature controlled boiler, the false pressure doesn't count, and the boiler will get up to temperature. You just need to flush the air out by purging the steam wand prior to steaming the first time. So on a PIDed machine, the vacuum breaker is more a convenience item than a necessity -- you can still put the machine on a timer and have it fire up without surprises

Just to add to this, a small warning that if you block off the vacuum breaker valve on a machine with temperature rather than pressure control, the pressure can possibly spike very high because of the air in the system. This might open up the steam boiler safety/over-pressure valve and make some noise until enough pressure is bled off that the air in the boiler makes the total pressure less than the point where the safety valve opens. Probably isn't a huge problem, but it's something to know. Also, make sure your safety valve is in good condition if you're doing this on an old linea. They can get stuck closed and that's probably not a good thing under any circumstances, but especially when you're intentionally leaving air in the boiler.