La Pavoni Pre-mil water heated grouphead mod

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TigerStripes

#1: Post by TigerStripes »

Hi all, wanted to share my easily reversible water heated grouphead mod. I have been using this for a few weeks on another machine and it has been working well. The group on pre-mil gets screaming hot after one or two shots. When converted to water heated, the group stays a reasonable temperature and doesn't scorch shots. I also tried out the "bong isolator" and found that it did too much isolating, resulting in a lot of half pumps needed to bring the group up to temperature for the first shot. The silicone isolator is a good middle ground, where the group easily warms up, but doesn't easily get too hot.

I used castin crafts molding silicone, which doesn't shrink or expand when curing. It is food safe and rated for up to 400f.



The first step was to mold the silicone around the dipper tube, resulting in this:



I then cut off the end of the isolator (where water enters the group/piston area). I also added a small layer of silicone around the isolator, which makes a very tight fit when you push the isolator into the group. When you screw the dipper tube into the isolator, the isolator pushes out against the group, and everything is firmly held in place, and doesn't let any water through.



This is what the isolator looks like before it gets installed. The isolator is pushed into the group, and then the dipper tube is pushed and screwed into the isolator.



This is the final, installed isolator in the group. The small piece I'm holding up, is what I cut off the isolator earlier, which creates a void in the group that water can occupy.



I have this mod on both my pavoni levers and I'm pretty happy with the water heated groups. I think the steam heated grouphead was a poor design choice from La Pavoni, but luckily it's easy to modify it.
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masterchief24

#2: Post by masterchief24 »

Wow, This is really nice.

coffeebaum

#3: Post by coffeebaum »

Hi, thanks for posting this, I like the idea of the moldable silicone and will have to get some of that to try this.

Two questions for you though: first, I assume you molded the silicone with the dip tube installed in the group-head?

Secondly, it's difficult to tell from the pics, but with your mod, is the group head area above the piston totally sealed off from the boiler? There were some posts (Heat control mod for 2nd Generation La Pavoni Levers) a few years ago where folks did something similar (note that I like your moldable silicone idea a bit better), but in those instances there were either holes cut to allow some pressure equalization or the dip tube, itself, was modified to allow water to fill the area above the piston. Thoughts on those? Thanks!

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TigerStripes (original poster)

#4: Post by TigerStripes (original poster) » replying to coffeebaum »

Yes, the molded silicone was first made with the dip tube installed - you can see the result of that in the second picture.

The end of the isolator is chopped off so that there is a small amount of space open for water to collect in the "neck" right before the grouphead. If you don't have this space, you cannot raise the lever. You can still do half pumps of the lever to bring hot water from the boiler through the dipper tube into the group - in order to heat up the grouphead.
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toolate

#5: Post by toolate »

aby chance you can do a video of that and what do you like btter about this approach?

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TigerStripes (original poster)

#6: Post by TigerStripes (original poster) » replying to toolate »

I don't have a video, but I like this approach because the grouphead does not ever get hotter than 90c, instead of 100c+ with a steam heated grouphead.
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toolate

#7: Post by toolate »

thanks
i cant see how you molded it into that shape...