Pump on Conti Comocafe does not work

[PaulTheRoaster]

Hi,
I bought a Conti Comocafe from EBay:
http://cgi.ebay.com/ws/eBayISAPI....=1&item=4461320633

Contrary to the auction text, the "pump" does not work.

There is a one-way valve in the cylinder that draws water from the kettle. The problem is that it returns water as well. I am having a difficult time fixing it. I tried to draw an image of it in a drawing tool but gave up, so I will describe it (but I imagine it is a common design).

At the bottom of the cylinder there is a channel drilled to the kettle. Above this lies a disc with 8 holes around the center (which seals around the circumference with an O-ring). It screws in with a special sort of screw that has a slot in the head for the sealing washer. The center of the washer is raised so that the outside of the washer lies flat with the disc. The washer also has 8 bumps that fit into the 8 holes in the disc. (FWIW, the bumps are much smaller than it looks in the photo below. I'd guess they're 0.1-0.2 mm tall.)

The O-ring was easy to replace, but I tried replacing the special raised washer with 8 bumps with a regular washer, and it didn't quite work. I tried putting the washer inside the slot in the head as well as below it.

Any advice? I could somehow put a one-way valve on the kettle side of the channel, but I'm not sure where I would find a small one (or how to build one).

Bottom of disc:

Top of disc, bottom of washer and screw:


The old washer doesn't even look that bad to me, but it is not doing its job.

Thanks,
-Paul

[mogogear]

Ahhhh. We wondered where that machine went Saw it on ebay also... You need Timo--------Timooo, are you out there??? I bet you can help out the Como owner!

[PaulTheRoaster]

I'm thinking maybe of ordering a generic check valve--the other end of the channel comes into the kettle through a metal tube with about a 1/4" diameter. The only problem is that the only NSF-rated check valve from McMaster is huge ...

[timo888]

Ahhhh. We wondered where that machine went Saw it on ebay also... You need Timo--------Timooo, are you out there??? I bet you can help out the Como owner!

I took a Tylenol PM for a headache and my lids are drooping. In my drowsiness I'm having a hard time following Paul's description of how things fit together. I need to see how the washer is fastened to the metal disc. Paul, if you could provide a picture of the washer + disk assembled and oriented in their actual direction, and also a picture of everything taken apart, so that the screw is not in the washer. Like an exploded parts diagram. I need to see the diameter of the screw head and how it holds the washer in place against the disk.

Also, is the kettle above the disk? Where is the piston cylinder in relation to the bottom of the kettle? Directly below it?

Also, if the washer cracks when you flex it between thumb and fingers it has lost its pliability and won't work. The one-way washers must be able to cleave to the portholes to seal them when the piston advances, and be able to pull away from the portholes when the piston retreats. Also, make sure there's no lubricant on the flat surface of the head of the piston. Wipe the piston head clean.

Regards
Timo

[PaulTheRoaster]

I took a Tylenol PM for a headache and my lids are drooping. In my drowsiness I'm having a hard time following Paul's description of how things fit together.

No need for excuses My technical writing ain't the best.

I need to see how the washer is fastened to the metal disc. Paul, if you could provide a picture of the washer + disk assembled and oriented in their actual direction, and also a picture of everything taken apart, so that the screw is not in the washer. Like an exploded parts diagram. I need to see the diameter of the screw head and how it holds the washer in place against the disk.

I hope that helps. (I need a new digital camera, too.)

Ascii art?

--- <- head of screw
| <- gap for washer
--- <- disc that holds washer from below (part of screw--not separate)
|
| <- threads
|


The point is that the washer is not screwed into the disc directly. It is held in place only by the gap in the head of the screw.

Also, is the kettle above the disk? Where is the piston cylinder in relation to the bottom of the kettle? Directly below it?

The kettle is above the disk and the cylinder. The entire cylinder is below the bottom of the kettle. (and about 1" behind.)

Also, if the washer cracks when you flex it between thumb and fingers it has lost its pliability and won't work. The one-way washers must be able to cleave to the portholes to seal them when the piston advances, and be able to pull away from the portholes when the piston retreats. Also, make sure there's no lubricant on the flat surface of the head of the piston. Wipe the piston head clean.

The washer doesn't crack. It is not cleaving to the portholes, though.

Also--I think perhaps you are misunderstanding something--the piston head doesn't touch the disc at all. The disc remains stationary. It fastens to the bottom of the cylinder. When the lever is pulled, the piston is raised, drawing water through this check valve. Then when the lever is released, this check valve is supposed to seal, and the water goes out through another channel to the group. (and another valve which seems to work so far.)

There was some scale on the disc that deformed the washer slightly. I removed the scale and sanded the surface of the disc. *shrug*

I greatly appreciate the help, and I hope this post makes the situation more clear.

[timo888]

After last night's headache and Tylenol PM, I'm not as bright eyed and bushy-tailed as I ought to be
I am still confused about which way is up.

The solution depends upon the orientation of the piston.

Peppina's piston is base-mounted so that the piston's downstroke is actually advancing towards the ceiling. It looked to me as if the Conti had a similar base-mounted piston, but I've never seen one opened up. If the Conti's piston were base-mounted, then the one-way valve assembly ought to be flipped over so that the washer is below the disk with the flat side of the disk facing down.

So we need to confirm the orientation of the piston. I'm fairly confident that it should be like this if the piston is base-mounted (but would feel more confident if I were looking at the machine opened up)

CEILING
.
.
.
RAISED NIPPLE OF METAL DISK
FLAT SIDE OF METAL DISK with portholes and center tap
Washer
collar on screw to press washer tightly against the flat surface of metal disk
screw head

V PISTON ^
V PISTON ^
V PISTON ^
.
.
.
.
BASE

COUNTERTOP

I think the washer fits between flat face of the disk and the collar of the screw. But I'd need to see a closeup.


In a base-mounted piston with a one-way valve assembly between the piston and a kettle above, when the piston retracts (with the downstroke of the lever) the piston head is moving away from the one-way washer and the suction would pull the pliable washer down away from the portholes, allowing water to flow into the piston chamber. When the piston advances, the washer would be pressed back against the portholes, sealing them, forcing the water to exit under pressure by some other port to the group.


Regards
Timo

[PaulTheRoaster]

The solution depends upon the orientation of the piston.

So actually the piston is mounted to the top of the machine.

So, timo, everything is exactly upside-down from your description.

ceiling

piston

port to group

washer

disc

port to kettle

bottom of cylinder


The piston initially is very nearly touching the washer. When you pull the lever, the piston is raised, drawing water into the cylinder. When the lever is relesed, the piston lowers, forcing water out the port to the group.

When I remove the valve and look at it closely, it looks like there is a slight gap between the washer and the disc, i.e., it is open. I thought perhaps it funcitoned like a vacuum breaker (and could be open at 0 pressure). But perhaps that's further confirmation it's broken.

[timo888]

I concluded that the piston cylinder ran from the base of the machine up to just below the kettle, offset back from it by about an inch, based on your earlier statement:

The kettle is above the disk and the cylinder. The entire cylinder is below the bottom of the kettle. (and about 1" behind.)

So actually the piston is mounted to the top of the machine.

So, timo, everything is exactly upside-down from your description

If the entire cylinder is below the bottom of the kettle, how can the piston be top-mounted and be above the kettle

Paul, have you been feeding me disinformation intentionally Have you been sent here by the HX contingent to mess with my mind?

Where is the piston head in its fully extended position? Just above the washer?

If your latest word-diagram is accurate

ceiling

piston

port to group

washer

disc

port to kettle

bottom of cylinder

water is being sucked up from the kettle and we'd have to remove the Conti from the list of gravity-fed machines.

Pictures of the machine taken apart, so the piston is visible, would be helpful.

Regards
Timo

[PaulTheRoaster]

I concluded that the piston cylinder ran from the base of the machine up to just below the kettle, offset back from it by about an inch, based on your earlier statement:

That's right.

The kettle is above everything.

There is a channel at the bottom of the cylinder that goes to the kettle.

f the entire cylinder is below the bottom of the kettle, how can the piston be top-mounted and be above the kettle Confused

Paul, have you been feeding me disinformation intentionally Question Have you been sent here by the HX contingent to mess with my mind? Smile

Where is the piston head in its fully extended position? Just above the washer?

Heh, I have not been sent here by the HX disinformation team

So ... the entire cylinder, piston, and check valve are below the kettle, but oriented upside down from the peppina.

In the fully extended position, the piston is just above the washer.

When you pull the lever, the piston is retracted.

water is being sucked up from the kettle and we'd have to remove the Conti from the list of gravity-fed machines.

Pictures of the machine taken apart, so the piston is visible, would be helpful.

The water is sucked down .... since the entire cylinder is below the kettle.

I will take some pictures later.

Mathias has some nice pictures: http://lm.steen.free.fr/html/photo_gallery-1.html but not of the piston and cylinder.

[timo888]

It looks as though the gravity-water-pressure from the kettle above fills the piston chamber, assisted by the hydraulic suction of the upwardly retreating piston-head. Then, with the chamber full of water, the piston advances downward, and water exits through the group port. If this is the case, then the one-way valve assembly should be positioned like this:


Screw head
collar
washer
flat side of disk with holes
nipple side of disk with holes

Is that how you have it?

When you say it doesn't work, what are the symptoms?

No water or feeble water stream at the dispersion screen?
An airy whooshing sound as the piston retracts?
A airy whooshing sound as the piston advances?

Is there a one-way valve to prevent backflow from the puck? If so, and it is not functioning, when the piston retracts, air would be sucked into the piston chamber through the port to the group; this would reduce the upward suction upon the one-way washer between piston chamber and kettle, and so tend to prevent water from being pulled up into the chamber.


Regards
Timo

[PaulTheRoaster]

It looks as though the gravity-water-pressure from the kettle above fills the piston chamber, assisted by the hydraulic suction of the upwardly retreating piston-head. Then, with the chamber full of water, the piston advances downward, and water exits through the group port. If this is the case, then the one-way valve assembly should be positioned like this:


Screw head
collar
washer
flat side of disk with holes
nipple side of disk with holes

Is that how you have it?

Mostly.

It is as you said, but I put the washer between the collar and the screw head. Actually I tried it both ways. (When I disassembled the cylinder, the washer was between the collar and screw head.)

If I put the washer below the collar, then when I tighten the screw the washer turns up. (I couldn't find a way to adjust the screw to get a seal between the collar and the washer, and between the washer and the disc.)

Also--there would be no need for a collar on the screw if the washer were supposed to lie below the collar.

When you say it doesn't work, what are the symptoms?

No water or feeble water stream at the dispersion screen?
An airy whooshing sound as the piston retracts?
A airy whooshing sound as the piston advances?

When I pull the lever, the water level in the kettle lowers as water goes into the cylinder. When I release the lever, water doesn't come out of the group valve, it returns into the kettle and the water level in the kettle rises.

When I manually fit the piston into the cylinder, water comes back out the channel into the kettle. (So the washer fails whether I use the full pressure of the spring, or the gentle pressure of manually fitting the piston into the cylinder.

There are no airy wooshing sounds.

Is there a one-way valve to prevent backflow from the puck? If so, and it is not functioning, when the piston retracts, air would be sucked into the piston chamber through the port to the group; this would reduce the upward suction upon the one-way washer between piston chamber and kettle, and so tend to prevent water from being pulled up into the chamber.

Yes, there is a one-way valve in the group to prevent backflow. It seems to be functioning. If I put my finger on the port in the kettle, then water comes out the group when I release the lever. Still, I don't want to have to put my finger in 198F water to pull a shot

Anyways, the problem is that the one-way washer in the kettle is letting water in and out all the time--I don't think the check valve in the grouphead has anything to do with it.


I might try to get some PVC pipe to hold down the washer just as a final test, but I am convinced the washer is bad. The tricky part is finding a replacement washer that is shaped just so.

Cheers,
-Paul

[timo888]

Your symptoms do seem to point to a defective one-way washer, or one that is not properly mounted. If the washer is seated between the collar and the screw head, and if that causes any gap between washer and disk, I would expect the symptoms you've described.

The washer must be perfectly flush against the flat side of the disk, or it is not going to stop the water from being expelled from the piston chamber back into the kettle upon the downstroke of the piston. It doesn't flex down as much as press against. Those rings on the washer are from repeated pressure. They're not plugs that were on the washer originally.

With regard to the collar and seating the washer beneath it: does the washer bend away from the plate with the slightest bit of pressure as the screw is tightened? Or does it happen only when you've fully tightened the screw?

Recommendation: find a thin washer with an inner diameter slight smaller than the diameter of the collar.
Finding washers the right size is harder than finding o-rings, and the search is made even harder if you add FDA approved materials into the mix. And when you do find them, you'd better want a couple of dozen or maybe a 100 of them because you won't find them at the hardware store but from online suppliers where there are always minimum quantity requirements to deal with.

In an old thread, Steve Robinson mentioned making washers DIY style. You could buy some thin EPDM PC sheets and sharpen yourself some copper tubes and have at it with a hammer. It won't matter much if the outer edge is jagged. It's the inner diameter cutout that's critical for the one-way washer to be seated properly and behave itself.

Regards
Timo

[PaulTheRoaster]

With regard to the collar and seating the washer beneath it: does the washer bend away from the plate with the slightest bit of pressure as the screw is tightened? Or does it happen only when you've fully tightened the screw?

This happens only if I position the washer under the collar. It seems not to take much pressure for it to turn up. I can play with this some more. Perhaps there is a way to get it to work. (Before I did anything, the washer was between the collar and the head, and the machine looked like no one had taken it apart since it was built.)

On the equivalent peppina valve does the inside of the washer touch the disc directly, or is there a collar or metal washer?

Recommendation: find a thin washer with an inner diameter slight smaller than the diameter of the collar.
Finding washers the right size is harder than finding o-rings, and the search is made even harder if you add FDA approved materials into the mix. And when you do find them, you'd better want a couple of dozen or maybe a 100 of them because you won't find them at the hardware store but from online suppliers where there are always minimum quantity requirements to deal with.

Uff, that doesn't sound fun. Actually 2 washers at my local hw store had inner diameters just smaller than the collar. (lucky me) But they were a bit thicker than the original washer.

The old washer does have sort of an indentation to make room for the collar and remain flat. I may try to recreate this with one of my new washers and a rotary tool somehow.

I suspect that in the end I'll just adapt a generic check valve on the other end of the channel.

(This is another thread, but is it "safe" to use non-NSF or FDA rated check valves whose only components are things like stainless steel and viton or rubber? Would a good soak in strong detergent remove any leftover oils from the machining process?)

-Paul

[timo888]

On the equivalent peppina valve does the inside of the washer touch the disc directly, or is there a collar or metal washer?

The Peppina's washer sits beneath the head of the screw, flush with the plate that contains the egress holes from the kettle. If it is not flush, it won't work. Water will escape the piston chamber in the gap, and the turbulence of the backflow, once the flow begins, prevents the washer from sealing. It's got to be touching to begin with.

I am a bit of a fanatic about food safety and toxicity. I'm extremely sensitive, generally speaking, to all kinds of chemicals. You wouldn't believe the stuff they put into household products, perfumes, colognes, lotions, etc ... petroleum-based chemicals that can be absorbed directly through the skin, or mucus membranes, or breathed in, which then enter the bloodstream and directly affect the central nervous system. Totally unregulated uses because not a food product. And yet when in the bloodstream they might as well have been ingested.

I don't know what kinds of chemicals you might find on a washer that was not intended for drinking water, and what would wash off with detergent. Me, I'd stick with EPDM PC. Should be fine if placed in a location a good distance away from the heating element. Good to 300F. But believe me, you CAN overheat an EPDM o-ring in an espresso machine if you leave the machine boiling for 5 minutes. The metal can get pretty hot if it is in direct contact with the heating element.

However, it might not do the trick for you if you place a one-way valve at the bottom of the machine. A good amount of water can be expelled from the piston chamber back towards the kettle, and you'd either not be getting all the water you needed and/or cooling it down by passing some of it twice through the conduit. There could be undesirable sife-effects to a modded design.

What are the relevant dimensions of the washer?

Regards
Timo

[PaulTheRoaster]

IT WORKS!

Okay, not entirely.

But, I found that the new washer I bought was not quite thick enough to take up all the space between the collar and the head of the screw. So I put in two new washers, and now that valve works.

Another part of the story is that the pf that was included came from a steam toy. It didn't quite fit, but it had the right diameter, so I filed the ears down until they fit and then stuck some rubber up the grouphead to take up some of the space.

Bad idea. It turns out that if anything between the group check valve and the dispersion screen is interfered with, the check valve either won't open when you want it to, or will open when you don't. (BTW, it is not just to prevent backflowing of water--the cylinder will much more happily fill itself with air than water if this valve won't close.)

But it seems that the cylinder valve is working if I can stall the lever by misadjusting the group valve.

Back to the portafilter--so the ears are not quite tall enough alone to press the filter up against the gasket. It seems that even if I add rubber bands and o-rings between the filter and the portafilter to make it a tight fit, the filter is still not mating with the o-ring around the dispersion screen that is the grouphead gasket. I will have to see if I can find a thicker o-ring and/or slip a very thin layer of rubber above it somehow without disturbing the delicate group valve.

Is it a bad idea to try to adapt a steam toy portafilter? (The kind where the filter has a line for a single or a double.) Over there -> in HX land they talk about different filters doing different things. I could perhaps get a 49 mm Europiccola filter to fit. Worth a try I think.


Before I forget, special thanks to Timo and Mathias!

[mogogear]

My head hurts!!!!! from reading all the descriptions you guys have been posting 1. Observing 2. Describing 3. Comprehending 4. repeat 5. Repeat....... Good focus My 49 year old eyes and 15 year old atttention span is tired.

[PaulTheRoaster]

My head hurts!!!!! from reading all the descriptions you guys have been posting 1. Observing 2. Describing 3. Comprehending 4. repeat 5. Repeat....... Good focus My 49 year old eyes and 15 year old atttention span is tired.

Heh, I understand. I felt that way reading the Peppina thread, but now that I've tinkered with my Comocafe everything in that thread is crystal clear.

(If only I were good with a CAD tool I could save a lot of confusion and head rubbing.)

Question: I definitely need a new filter basket, probably a new portafilter too. The filter should probably be around 49 mm. Portafilter ID around 52. Anything cheaper than the Europiccola portafilter? Oh, it has to have 3 ears, too.

[timo888]

IT WORKS!

Okay, not entirely.

But progress is good.

It turns out that if anything between the group check valve and the dispersion screen is interfered with, the check valve either won't open when you want it to, or will open when you don't. (BTW, it is not just to prevent backflowing of water--the cylinder will much more happily fill itself with air than water if this valve won't close.)

That's why I was asking you about any airy whooshing sounds.

If the group valve is working, the piston, when it retracts, will be able to draw water from the kettle. If the group valve is not working, the piston draws mostly air.

If the piston has drawn water, and if the cylinder valve is working (i.e. closes properly), the piston will be able to push the water to the group. If the cylinder valve is not working (i.e. fails to close properly), much of the water in the piston chamber will go back towards the kettle and only a feeble amount will go to the group.

But it seems that the cylinder valve is working if I can stall the lever by misadjusting the group valve.

I assume you mean here that the spring-piston cannot push water through the dispersion screen (when the PF is empty for testing purposes). If the machine is stalled in that manner, it means that the group valve is not opening or that the PF is otherwise blocked. The cylinder valve is not implicated in that sort of stall in this design:

ceiling

piston

port to group

washer

disc

port to kettle

bottom of cylinder

The downstroke of the piston would send water to the group if the cylinder washer were closed, and would send water back to the kettle if the cylinder washer were open. Neither of these scenarios produces the stall effect, i.e. where water can't exit the group.

Regards
Timo

[PaulTheRoaster]

The downstroke of the piston would send water to the group if the cylinder washer were closed, and would send water back to the kettle if the cylinder washer were open. Neither of these scenarios produces the stall effect, i.e. where water can't exit the group.

Maybe I wasn't making myself clear--
I accidentally misadjusted the group valve so it wouldn't open.
Then when I pull the lever, water enters the cylinder through the cylinder valve. When I release the lever, the lever stalls, because the water in the cylinder has nowhere to go.

When I then backed out the screw on the group valve all the water released.

This makes me thing my repair to the cylinder valve worked. It's good to know that it doesn't leak at all under full pressure.

(I also did notice the whooshy sounds when I had the group valve misadjusted too far in the opposite direction.)

Now to find a smaller filter.

BTW, Timo, I was reading through the Peppina thread. It is uncanny how similar these two machines are.

-Paul

[timo888]

This makes me thing my repair to the cylinder valve worked. It's good to know that it doesn't leak at all under full pressure.

It is a good sign that the cylinder valve holds when the group valve is closed. It may seem that a stall puts the cylinder washer through a stress test. But, with this type of valve, paradoxically the real stress test occurs when the cylinder valve is under normal stress, i.e. when then group valve is open.

For optimal water flow to the puck, the washer in the piston cylinder should be delicate and pliant enough to "sense" the piston's downstroke immediately and yet be not so flimsy that turbulence of the water in the piston chamber would dislodge it, breaking the seal. For if the seal is broken, water flows out of the piston chamber in two directions, towards the group but also back towards the kettle, resulting in less than the optimal amount of water reaching the puck. This bifurcated flow also lowers brew pressure.

This can happen on the Peppina if the washer in the piston cylinder is working but not optimally. As you say, the two machines are quite similar, so this problem could also affect the Conti -- unless that little collar on the screw solves the problem by adding some stability to the washer? I don't understand what it does that the screw head wouldn't also do.

So much depends
upon the black
rubber washer
glazed with brew
water
inside the piston
chamber.

With apologies to William Carlos Williams

Regards
Timo