The blue line is the pump suction, low pressure
The 3rd photo is the pump supply, high pressure
This line goes to a T. One side of the T goes to the side of the boiler for the water inlet the other leg of the T is for air release this is the yellow line
Now comes the tricky part
The large brass T on the opposite side of the boiler is a combination, one side the steam valve with the steam wand connected on the bottom the other goes to the 3 way valve
There is a one way valve where the boiler water enters the brew head
So, you turn on the pump to pull a shot, the pump ramps up the pressure in the boiler, as the pressure increases the one way valve is forced open and water hits the coffee. You turn off the pump and the 3 way valve opens, this releases the pressure in the boiler and the one way valve closes stopping any additional water from entering the portafilter, water released by the 3 way valve, this is the tricky part, the bottom side of the valve drains the excess water, the red tube in your photo equalizes the pressure in the boiler and atmosphere.
This keeps the 3 way valve from draining the boiler.
Another way, the boiler holds about 200ml of water at atmospheric pressure, at 9 bar there are a couple extra ml of water squeezed in the boiler. The 3 way valve releases the pressure the extra few ml of water are drained and the boiler returns to its operating pressure.
This is not working like any other 3 way valve. Because the portafilter mounts directly to the bottom of the boiler there is no brew water path that can be interrupted with a 3 way valve as in other machines. So, the LeLit people built a work around. The answer to your question about dirty water re-entering the boiler is no.

This is the copper pipe that runs through the middle of the boiler, via the 1st-line parts list.



This is my photoshopped version of the layout for clarity. Some of the surfaces may look a little goofy, but I removed all of the obstructing wires and darkened the background.

Frost wrote:(from the top of the boiler, then running external to the boiler, then piped back through the boiler to the group.... ) I wonder how that works for brew temp stability....

Me too. Running the machine with the top off today I noticed that the teflon red-marked pipe does not pre heat with the boiler. I think it would be a good idea to flush some water through to heat it up.

JmanEspresso wrote:The Red Marked tube, I would think, is to feed how water out of the steam arm... No?

I though so at first as well, but I believe you are incorrect. The red-marked tube screws into the copper pipe directly, which then goes through the boiler to the group. Hot water comes from the boiler through the bottom brass T-joint, then out the steam wand directly below the joint.

Zircote, your description may be mostly accurate, but I am having trouble following it. I'm pretty sure that there are no one-way valves in the system. Only the three way solenoid. Also, the red tube is on an independent system from the boiler itself. The two are linked only through the solenoid in terms of water contact.

That copper pipe-MC027 screws into the one way valve which is at the base of the boiler-MC136. The top of the tube sits in the middle of the heating element so it picks up the hottest water in the boiler when the pump is turned on. The boiler water is pumped through the tube, through the one way- spring valve to the dispersion screen and into the brew head. Without the one way valve the water would drip out of the boiler. If you ever crack open your boiler to descale it you will see the connection. By removing the dispersion screen you should be able to see up into the one way- spring check valve.
My description of the process was a bit difficult.
There is no connection between the brew head and the 3 way valve. If there were a connection then there would be no connection to the top of the boiler, because it would be mixing waste water with fresh water, which you can see is not happening.
When the 3 way valve is in the brewing position the pressure is held in the boiler. The pump is activated for a shot, pressure rises, the shot is finished and the 3 way is activated, boiler pressure is released into the 3 way valve via the T connected to the steam valve at the top of the boiler. To prevent air pockets from forming in the boiler only the volume of water that creates the pressure in the boiler should be released and disposed of. But when the valve opens a much larger volume of water, because of the pressure, wants to escape. By tying the back side of the 3 way valve- red tube- back to the top of the boiler the pressure on both sides of the 3 way will equalize with the minimum loss of water volume to the drain. No air gap, and no excess pressure.
The red tube is connected only to the top of the boiler and will not heat because there is no movement of water in the tube. When the 3 way valve is closed the tube is closed and no movement. When the 3 way valve opens the quantity of water that could move into the tube is very small so heating will not be easy to notice. The direction of flow when the 3 way valve opens is through the T at the top of the boiler to the 3 way valve. So, the red tube is returning water to the boiler, not vis versa.
I hope that was a better description. If you crack the boiler it will be obvious and make a lot more sense than my convoluted description.

Your pictures are great. Are you using a macro lens to get the depth of field?
I forgot to mention the pipe MC027 is very small, 1.5" long and 1/8" OD, + or -, the parts photo makes it look gigantic.

Zircote wrote:That copper pipe-MC027 screws into the one way valve which is at the base of the boiler-MC136. The top of the tube sits in the middle of the heating element so it picks up the hottest water in the boiler when the pump is turned on. The boiler water is pumped through the tube, through the one way- spring valve to the dispersion screen and into the brew head. Without the one way valve the water would drip out of the boiler. If you ever crack open your boiler to descale it you will see the connection. By removing the dispersion screen you should be able to see up into the one way- spring check valve.
My description of the process was a bit difficult.
There is no connection between the brew head and the 3 way valve. If there were a connection then there would be no connection to the top of the boiler, because it would be mixing waste water with fresh water, which you can see is not happening.
When the 3 way valve is in the brewing position the pressure is held in the boiler. The pump is activated for a shot, pressure rises, the shot is finished and the 3 way is activated, boiler pressure is released into the 3 way valve via the T connected to the steam valve at the top of the boiler. To prevent air pockets from forming in the boiler only the volume of water that creates the pressure in the boiler should be released and disposed of. But when the valve opens a much larger volume of water, because of the pressure, wants to escape. By tying the back side of the 3 way valve- red tube- back to the top of the boiler the pressure on both sides of the 3 way will equalize with the minimum loss of water volume to the drain. No air gap, and no excess pressure.
The red tube is connected only to the top of the boiler and will not heat because there is no movement of water in the tube. When the 3 way valve is closed the tube is closed and no movement. When the 3 way valve opens the quantity of water that could move into the tube is very small so heating will not be easy to notice. The direction of flow when the 3 way valve opens is through the T at the top of the boiler to the 3 way valve. So, the red tube is returning water to the boiler, not vis versa.
I hope that was a better description. If you crack the boiler it will be obvious and make a lot more sense than my convoluted description.

There is NO, repeat NO one-way valve at the base of the boiler. You're thinking about machines like the Nemox Fenice, which don't have the solenoid valve and pipe through the middle of the boiler arrangement. On the PL041 you can remove the showerscreen and poke a thin, flexible wire all the way up through the copper tube and into the teflon tube with no problem.

The short teflon tube does get hot when you're pulling shots as the hot water is flowing out of the boiler, into the 3-way valve and down through the copper pipe to the water distributor nut and showerscreen. Water NEVER flows directly into or out of the boiler via the teflon tube.

Part of my business is importing, selling and servicing these machines, something I've been doing for over 15 years.

Alan

Zircote wrote:Your pictures are great. Are you using a macro lens to get the depth of field?

Nope. My 6mp snapshot camera does pretty well. I'm right at the edge of it's focus range. Lots of lighting as well.

Alan Frew wrote:There is NO, repeat NO one-way valve at the base of the boiler.

Yes, I'm going to have to defer to and agree with Alan. I've also discovered that the red-marked tube becomes hot after the pump runs for a couple of seconds (it is quite apparent). The way that he describes the water flow makes the most sense to me, especially after you play around with the brew and hot water switches.

I do understand what you are describing now though - it's just not what happens in this particular machine.

My apologies, it seems they have changed something since I last looked inside one.
I would be very interested to know how they keep the waste water from the top of a used puck from remixing with clean water from the boiler for each successive shot.
From Mr Frew's description the 3 way valve is in the brew path.

Lots of light works wonders for the depth of field. A 6mp camera in the right hands....

I think if you re-read Alan's original post with fresh eyes, it will be clear to you.

Basically, the red-marked tube connects directly to the copper pipe, which goes through the boiler (no contact with boiler water) to the group. Brew water follows this path in reverse when released by the solenoid.

Overall this was a fun discussion though. I've gained a lot of insight into the mechanics and thermal properties of my machine. Thanks, all!

[quote="Alan Frew"]
Your PL041 is a bit different from those I just received, mainly due to repositioning the steam valve and knob off to the right hand side and eliminating the attached tamper to free up the internal space. However, the fundamental logic of the water flow hasn't changed.

I couldn't help but notice this comment! Alan, are we looking at the insides of the new Lelit PL041 here?

Alan, are we looking at the insides of the new Lelit PL041 here?

Not as far as I know. Certainly didn't come with the new steam wand.

Alan