I got my Bacchi last fall. Until I find my next desktop machine, it's my daily driver and I've got about 400-500 double shots through it.

It is an inspired design and Londoniun had very good customer service. When it is working correctly, the shots are in the Pavoni neighborhood.

After a couple of months, it started leaking steam from the bottom seal. This usually happened dramatically when I would touch the knob to pull the shot. Big puff of steam down into the flame. The shot would pull but not at full pressure. Usually disappointing and blond.

I tried tightening more, tightening less, removing,cleaning, and replacing the o-ring, a new o-ring, a new larger diameter o-ring. The last (new larger diameter o-ring) helped for about a month. It also seemed to help to store the unit with the pressure off the o-ring overnight so it has a chance to recover its original shape.

It recently got to the point that I couldn't use it any more. Every shot is ruined by the release of steam either while it is heating or when I touch it to brew. And the steam always releases from the front center of the unit regardless of the orientation of the piston portion.

Today I took the base apart and placed the bottom plate on a granite reference stone (flat to .001 millimeters per meter). Sure enough, the base is bowed in the way I expected. Looks like pulling up on the sides has distorted it so it bows down in the middle. Just enough to see light through I don't have the appropriate tools handy to measure the distortion.

I'm going to get some sandpaper and flatten it on the reference stone. Looks like there is enough lip to be able to sacrifice some.

I hope this is helpful. I'll report back with results.

Regards

Tom

Have you tried filling the base less? I get this problem when using the Bacchi on uneven ground when camping, and as long as the water is just touching the bottom of the "fill mark" (and indeed even with a fraction less), all is fine. If I fill it just a touch more, I get the same problem you are reporting. The Bacchi is quite sensitive to this.

Cheers

Mike

Thanks Mike. I'll try that. I measure out 1 oz in a shot cup for consistency.

I ground it down with 60 grit. The place it was leaking was the last to reach the paper.

I took it down to 300 grit. Works better but seems to have a generalized leak now. I suspect I need to polish it to 600 grit or put a high temp gasket sealant to lube the o-ring.

Interesting when I get it up to temp and rock it back and forth, the water seals it and it starts to whistle.

Tom, I've been having the same problem as you. Several months of good use and great coffee, now steam escaping from the bottom boiler. At first, I still got the whistle after 6 minutes even with steam escaping during heating. But now I don't get that, so pretty much useless. You say your base bowed because of pulling up on the sides? I don't get what you mean. How exactly could my base have become bowed - if this is in fact what has happened?

I've already replaced the o-ring once; I'll try Mike's tip and perhaps get hold of some food-grade lubricant.

Anthony

aodonnell wrote:You say your base bowed because of pulling up on the sides? I don't get what you mean. How exactly could my base have become bowed - if this is in fact what has happened?

As far as I can tell, when you tighten the top knob, it pushes down on the center of the assembly and pulls up on both round bars on the sides. These in turn pull up on the base at each side. And so the base takes on a curve. The bending pressure combined with the heat apparently allow it to give way. Once it does, no more 9 bars pressure. Imagine putting your foot on a paper plate and pulling up on the sides. Does that make sense?

I think my refinishing solution will work once I polish the surface up enough to from a good seal. Although, it may bend again once subjected to heat and pressure.

It looks like a design defect. Renders the thing useless unless fixed. Fortunately, the fix is pretty easy if they are willing to re-engineer the piece. It's easy to replace. The base needs to retain it's shape for the system to work. Either another material or thicker aluminum. While they are fixing this, they could make the base a little bigger, and concave, to allow it to catch more of the heat off the burner flame.

Lubing the o-ring is a very good idea, as is lubing the piston - if that gets stiff it is obviously going to require that much more steam pressure.

There's no need for the top knob to be done up so tight that it exerts a force nearly substantial enough to bow the base.

Even interesting mistakes on my part - like forgetting to fill the base or plunging the hot Bacchi into very cold water to immediately prepare new shots has not had any effect on the base.

I agree that it shouldn't be necessary to overtighten. This issue sneaks up on you. As the base starts to bend, it releases steam once in a while, then more often. Each time leads you to tighten a little more to avoid the problem. And so it goes. Until it won't keep a seal at all.

I'm new here, but thought I'd chime in. I have the Bacchi and had the same problem. The answer is to lube the piston.

My piston seems to move freely with just water as lubrication. What do you use?

In Europe it's called Molykote 111 and in the US I think it's called Dow Corning 111. I originally used rice bran oil on the outer side of the piston and it worked fine. But the Molykote is proper food grade grease. So you can use it in the inside of the piston where it comes in contact with the drinking water.

The piston will move by hand without lubrication, but the steam pressure is not enough to overcome the drag, so you get back pressure that escapes through the base.